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1. Spin decoherence and off-resonance behavior of radiofrequency-driven spin rotations in storage rings

Author: Nikolaev, N. N., Rathmann, F., Slim, J., Andres, A., Hejny, V., Nass, A., Kacharava, A., Lenisa, P., Pretz, J., Saleev, A., Shmakova, V., Soltner, H., Abusaif, F., Aggarwal, A., Aksentev, A., Alberdi, B., Barion, L., Bekman, I., Beyß, M., Böhme, C., Breitkreutz, B., Canale, N., Ciullo, G., Dymov, S., Fröhlich, N. -O., Gebel, R., Gaisser, M., Grigoryev, K., Grzonka, D., Hetzel, J., Javakhishvili, O., Kamerdzhiev, V., Karanth, S., Keshelashvili, I., Kononov, A., Laihem, K., Lehrach, A., Lomidze, N., Lorentz, B., Macharashvili, G., Magiera, A., Mchedlishvili, D., Melnikov, A., Müller, F., Pesce, A., Poncza, V., Prasuhn, D., Shergelashvili, D., Shurkhno, N., Siddique, S., Silenko, A., Stassen, S., Stephenson, E. J., Ströher, H., Tabidze, M., Tagliente, G., Valdau, Y., Vitz, M., Wagner, T., Wirzba, A., Wrońska, A., Wüstner, P., and Żurek, M.
Subjects: Physics - Accelerator Physics, High Energy Physics - Experiment, Nuclear Experiment
Abstract: Radiofrequency-driven resonant spin rotators are routinely used as standard instruments in polarization experiments in particle and nuclear physics. Maintaining the continuous exact parametric spin-resonance condition of the equality of the spin rotator and the spin precession frequency during operation constitutes one of the challenges. We present a detailed analytic description of the impact of detuning the exact spin resonance on the vertical and the in-plane precessing components of the polarization. An important part of the formalism presented here is the consideration of experimentally relevant spin-decoherence effects. We discuss applications of the developed formalism to the interpretation of the experimental data on the novel pilot bunch approach to control the spin-resonance condition during the operation of the radiofrequency-driven Wien filter that is used as a spin rotator in the first direct deuteron electric dipole moment measurement at COSY. We emphasize the potential importance of the hitherto unexplored phase of the envelope of the horizontal polarization as an indicator of the stability of the radiofrequency-driven spin rotations in storage rings. The work presented here serves as a satellite publication to the work published concurrently on the proof of principle experiment about the so-called pilot bunch approach that was developed to provide co-magnetometry for the deuteron electric dipole moment experiment at COSY., Comment: 31 pages, 10 figures, 5 tables
Published: 2023

2. Pilot bunch and co-magnetometry of polarized particles stored in a ring

Author: Slim, J., Rathmann, F., Andres, A., Hejny, V., Nass, A., Kacharava, A., Lenisa, P., Nikolaev, N. N., Pretz, J., Saleev, A., Shmakova, V., Soltner, H., Abusaif, F., Aggarwal, A., Aksentev, A., Alberdi, B., Barion, L., Bekman, I., Beyß, M., Böhme, C., Breitkreutz, B., Canale, N., Ciullo, G., Dymov, S., Fröhlich, N. -O., Gebel, R., Gaisser, M., Grigoryev, K., Grzonka, D., Hetzel, J., Javakhishvili, O., Kamerdzhiev, V., Karanth, S., Keshelashvili, I., Kononov, A., Laihem, K., Lehrach, A., Lomidze, N., Lorentz, B., Macharashvili, G., Magiera, A., Mchedlishvili, D., Melnikov, A., Müller, F., Pesce, A., Poncza, V., Prasuhn, D., Shergelashvili, D., Shurkhno, N., Siddique, S., Silenko, A., Stassen, S., Stephenson, E. J., Ströher, H., Tabidze, M., Tagliente, G., Valdau, Y., Vitz, M., Wagner, T., Wirzba, A., Wrońska, A., Wüstner, P., and Żurek, M.
Subjects: Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract: In polarization experiments at storage rings, one of the challenges is to maintain the spin-resonance condition of a radio-frequency spin rotator with the spin-precessions of the orbiting particles. Time-dependent variations of the magnetic fields of ring elements lead to unwanted variations of the spin precession frequency. We report here on a solution to this problem by shielding (or masking) one of the bunches stored in the ring from the high-frequency fields of the spin rotator, so that the masked pilot bunch acts as a co-magnetometer for the other signal bunch, tracking fluctuations in the ring on a time scale of about one second. While the new method was developed primarily for searches of electric dipole moments of charged particles, it may have far-reaching implications for future spin physics facilities, such as the EIC and NICA., Comment: 5 pages, 3 figures + references + supplemental material (6 pages, 2 figures, 6 tables + references)
Published: 2023

3. Spin Physics at COSY (2021-2024 and beyond) -- Pathfinder investigations toward an EDM storage ring and Spin-for-FAIR

Author: Gebel, R., Hejny, V., Kacharava, A., Lehrach, A., Lenisa, P., Nass, A., Pretz, J., Rathmann, F., Ströher, H., Keshelashvili, I., Stephenson, E. J., Filatov, A. Wrońska Y., Kondratenko, A., Kondratenko, M., Nikolaev, N., Melnikov, A., Senichev, Y., Aksentyev, A., Butenko, A., Syresin, E., Saleev, A., Shmakova, V., Karanth, S., Breitkreutz, B., Shurkhno, N., Stassen, R., and Pesce, A.
Subjects: Physics - Accelerator Physics, Nuclear Experiment
Abstract: The unique global feature of COSY is its ability to accelerate, store and manipulate polarized proton and deuteron beams. In the recent past, these beams have been used primarily for precision measurements, in particular in connection with the study of charged particle EDMs (Electric Dipole Moment) in storage rings. The role of COSY as a R&D facility and for initial (static and oscillating) EDM measurements can hardly be overestimated. Unfortunately, as a consequence of the strategic decisions of Forschungszentrum J\"ulich and the subsequent "TransFAIR" agreement between FZJ and GSI Darmstadt, it is currently planned to stop the operation of COSY by the end of 2024. The various groups working with polarized beams at COSY felt it important to collect information on essential measurements to be performed until the termination of machine operation. These experiments, briefly described in this document along with an estimate of the beam time required, serve as pathfinder investigations toward an EDM storage ring and Spin for FAIR., Comment: 40 pages, 17 figures
Published: 2021

4. First detection of collective oscillations of a stored deuteron beam with an amplitude close to the quantum limit

Author: Slim, J., Nikolaev, N. N., Rathmann, F., Wirzba, A., Nass, A., Hejny, V., Pretz, J., Soltner, H., Abusaif, F., Aggarwal, A., Aksentev, A., Andres, A., Barion, L., Ciullo, G., Dymov, S., Gebel, R., Gaisser, M., Grigoryev, K., Grzonka, D., Javakhishvili, O., Kacharava, A., Kamerdzhiev, V., Karanth, S., Keshelashvili, I., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Magiera, A., Mchedlishvili, D., Müller, F., Pesce, A., Poncza, V., Prasuhn, D., Saleev, A., Shmakova, V., Ströher, H., Tabidze, M., Tagliente, G., Valdau, Y., Wagner, T., Weidemann, C., Wrońska, A., and Żurek, M.
Subjects: Nuclear Experiment, Quantum Physics
Abstract: We investigated coherent betatron oscillations of a deuteron beam in the storage ring COSY, excited by a detuned radio-frequency Wien filter. The beam oscillations were detected by conventional beam position monitors. With the currently available apparatus, we show that oscillation amplitudes down to \SI{1}{\micro \meter} can be detected. The interpretation of the response of the stored beam to the detuned radio-frequency Wien filter is based on simulations of the beam evolution in the lattice of the ring and realistic time-dependent 3D field maps of the Wien filter. Future measurements of the electric dipole moment of protons will, however, require control of the relative position of counter-propagating beams in the sub-picometer range. Since here the stored beam can be considered as a rarefied gas of uncorrelated particles, we moreover demonstrate that the amplitudes of the zero-point (ground state) betatron oscillations of individual particles are only a factor of about 10 larger than the Heisenberg uncertainty limit. As a consequence of this, we conclude that quantum mechanics does not preclude the control of the beam centroids to sub-picometer accuracy. The smallest Lorentz force exerted on a single particle that we have been able to determine is \SI{10}{aN}., Comment: 20 pages, 16 figures
Published: 2021
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5. A New Beam Polarimeter at COSY to Search for Electric Dipole Moments of Charged Particles

Author: Müller, F., Javakhishvili, O., Shergelashvili, D., Keshelashvili, I., Mchedlishvili, D., Abusaif, F., Aggarwal, A., Barion, L., Basile, S., Böker, J., Canale, N., Ciullo, G., Dymov, S., Felden, O., Gagoshidze, M., Gebel, R., Demary, N., Grigoryev, K., Grzonka, D., Hahnraths, T., Hejny, V., Kacharava, A., Kamerdzhiev, V., Karanth, S., Kulikov, A., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Macharashvili, G., Magiera, A., Metreveli, Z., Nass, A., Nikolaev, N. N., Nioradze, M., Pesce, A., Poncza, V., Prasuhn, D., Pretz, J., Rathmann, F., Saleev, A., Sefzick, T., Senichev, Yu., Shmakova, V., Slim, J., Soltner, H., Stephenson, E., Ströher, H., Tabidze, M., Tagliente, G., Uzikov, Yu., Valdau, Yu., Wagner, T., Wrońska, A., Wüstner, P., and Żurek, M.
Subjects: Physics - Instrumentation and Detectors, High Energy Physics - Experiment, Nuclear Experiment
Abstract: A calorimetric polarimeter based on inorganic LYSO scintillators is described. It has been designed for use in a storage ring to search for electric dipole moments (EDM) of charged particles such as the proton and deuteron. Its development and first use was on the Cooler Synchrotron (COSY) at the Forschungszentrum J\"ulich with 0.97 GeV/c polarized deuterons, a particle and energy suitable for an EDM search. The search requires a polarimeter with high efficiency, large analyzing power, and stable operating characteristics. With typical beam momenta of about 1 GeV/c, the scattering of protons or deuterons from a carbon target into forward angles becomes a nearly optimal choice of an analyzing reaction. The polarimeter described here consists of 52 LYSO detector modules, arranged in 4 symmetric blocks (up, down, left, right) for energy determination behind plastic scintillators for particle identification via energy loss. The commissioning results of the current setup demonstrate that the polarimeter is ready to be employed in a first direct search for an EDM on the deuteron, which is planned at COSY in the next two years.
Published: 2020
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6. Beam-based alignment at the Cooler Synchrotron COSY as a prerequisite for an electric dipole moment measurement

Author: Wagner, T., Nass, A., Pretz, J., Abusaif, F., Aggarwal, A., Andres, A., Bekman, I., Canale, N., Ciepal, I., Ciullo, G., Dahmen, F., Dymov, S., Ehrlich, C., Gebel, R., Grigoryev, K., Grzonka, D., Hejny, V., Hetzel, J., Kacharava, A., Kamerdzhiev, V., Karanth, S., Keshelashvili, I., Kononov, A., Kulikov, A., Laiham, K., Lehrach, A., Lenisa, P., Lomidze, N., Magiera, A., Mchedlishvili, D., Müller, F., Nikolaev, N. N., Pesce, A., Poncza, V., Rathmann, F., Retzlaff, M., Saleev, A., Schmühl, M., Shergelashvili, D., Shmakova, V., Slim, J., Stahl, A., Stephenson, E., Ströher, H., Tabidze, M., Tagliente, G., Talman, R., Uzikov, Yu., Valdau, Yu., and Wrońska, A.
Subjects: Physics - Accelerator Physics
Abstract: The J\"ulich Electric Dipole moment Investigation (JEDI) collaboration aims at a direct measurement of the Electric Dipole Moment (EDM) of protons and deuterons using a storage ring. The measurement is based on a polarization measurement. In order to reach highest accuracy, one has to know the exact trajectory through the magnets, especially the quadrupoles, to avoid the influence of magnetic fields on the polarization vector. In this paper, the development of a beam-based alignment technique is described that was developed and implemented at the COoler SYnchrotron (COSY) at Forschungszentrum J\"ulich. Well aligned quadrupoles permit one to absolutely calibrate the Beam Position Monitors (BPMs). The method is based on the fact that a particle beam, which does not pass through the center of a quadrupole, experiences a deflection. The precision reached by the method is approximately 40 micro meter. Some consequences for the design of a new high precision storage ring for EDM mesasurements are discussed., Comment: Submitted to "Journal of Instrumentation (JINST)"
Published: 2020
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7. Search for the $\eta$ mesic $^3$He in the $pd\rightarrow d p \pi^{0}$ reaction with the WASA-at-COSY facility

Author: Adlarson, P., Augustyniak, W., Bashkanov, M., Bass, S. D., Bergmann, F. S., Berlowski, M., Bondar, A., Buscher, M., Calen, H., Ciepal, I., Clement, H., Czerwinski, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Fohl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Heijkenskjold, L., Hejny, V., Husken, N., Hirenzaki, S., Johansson, T., Kamys, B., Kelkar, N. G., Kemmerling, G., Khoukaz, A., Khreptak, A., Kirillov, D. A., Kistryn, S., Kleines, H., Klos, B., Krzemien, W., Kulessa, P., Kupsc, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Morsch, H. -P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Ritman, J., Roy, A., Rundel, O., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Stroher, H., Szczurek, A., Wolke, M., Wronska, A., Wustner, P., Yamamoto, A., Zabierowski, J., Zielinski, M. J., Zlomanczuk, J., and Zurek, M.
Subjects: Nuclear Experiment
Abstract: The excitation function for the $pd\rightarrow$ $d p \pi^{0}$ reaction has been measured by WASA-at-COSY experiment with the aim of searching for $^{3}\hspace{-0.03cm}\mbox{He}$-$\eta$ mesic nuclei. The measurement in the vicinity of $\eta$ meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the $\eta$-mesic Helium decays via the formation of an intermediate N$^{*}$(1535) resonance. No direct signal of the $\eta$-mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the $pd\rightarrow$ $(^{3}\hspace{-0.03cm}\mbox{He}$-$\eta)_{bound} \rightarrow$ $d p \pi^{0}$ process. It varies between 13 nb to 24 nb for the bound state with width in the range $\Gamma \in (5,50)$ MeV.
Published: 2020
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8. Differential Cross Sections for Neutron-Proton Scattering in the Region of the $d^*(2380)$ Dibaryon Resonance

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. --O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hodana, M., Höistad, B., Hüsken, N., Jany, A., Jany, B. R., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krapp, M., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yurev, L., Zabierowski, J., Zink, A., Złomańczuk, J., {Ż}uprański, P., {Ż}urek, M., Workman, R. L., Briscoe, W. J., Strakovsky, I. I., and Švarc, A.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec{n}p$ scattering performed in the energy region of the $d^*(2380)$ dibaryon resonance covering the the range of beam energies $T_n$ = 0.98 - 1.29 GeV ($\sqrt s$ = 2.32 - 2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process $dp \to np + p_{spectator}$. That way the $np$ differential cross section $\sigma(\Theta)$ was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power $A_y(\Theta)$ measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled $^3D_3 - ^3G_3$ waves.
Published: 2020
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9. Measurement of deuteron carbon vector analyzing powers in the kinetic energy range 170-380 MeV

Author: JEDI Collaboration, Müller, F., Zurek, M., Bagdasarian, Z., Barion, L., Berz, M., Ciepal, I., Ciullo, G., Dymov, S., Eversmann, D., Gaisser, M., Gebel, R., Grigoryev, K., Grzonka, D., Hejny, V., Hempelmann, N., Hetzel, J., Hinder, F., Kacharava, A., Kamerdzhiev, V., Keshelashvili, I., Koop, I., Kulikov, A., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Maanen, P., Macharashvili, G., Magiera, A., Mchedlishvili, D., Nass, A., Nikolaev, N. N., Pesce, A., Prasuhn, D., Pretz, J., Rathmann, F., Rolando, V., Rosenthal, M., Saleev, A., Schmidt, V., Senichev, Y., Shergelashvili, D., Shmakova, V., Silenko, A., Slim, J., Soltner, H., Stahl, A., Stassen, R., Stephenson, E., Ströher, H., Tabidze, M., Tagliente, G., Talman, R., Trinkel, F., Uzikov, Yu., Valdau, Yu., Valetov, E., Weidemann, C., Wronska, A., and Wüstner, P.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: A measurement of vector analyzing powers in elastic deuteron-carbon scattering has been performed at the Cooler Synchrotron COSY of Forschungszentrum J\"ulich, Germany. Seven kinetic beam energies between 170 and 380 MeV have been used. A vector-polarized beam from a polarized deuteron source was injected, accelerated to the final desired energy and stored in COSY. A thin needle-shaped diamond strip was used as a carbon target, onto which the beam was slowly steered. Elastically scattered deuterons were identified in the forward direction using various layers of scintillators and straw tubes. Where data exist in the literature (at 200 and 270 MeV), excellent agreement of the angular shape was found. The beam polarization of the presented data was deduced by fitting the absolute scale of the analyzing power to these references. Our results extend the world data set and are necessary for polarimetry of future electric dipole moment searches at storage rings. They will as well serve as an input for theoretical description of polarized hadron-hadron scattering.
Published: 2020

10. Influence of electron cooling on the polarization lifetime of a horizontally polarized storage ring beam

Author: Karanth, S., Stephenson, E., Wronska, A., Ciullo, G., Dymov, S., Gebel, R., Guidoboni, G., Hejny, V., Kacharava, A., Keshelashvili, I., Kulessa, P., Lenisa, P., Lehrach, A., Lorentz, B., Mchedlishvili, D., Nass, A., Nikolaev, N., Pesce, A., Pretz, J., Prasuhn, D., Rathmann, F., Saleev, A., Senichev, Y., Shmakova, V., Stroeher, H., Talman, R., Valdau, Yu., Weidemann, C., and Wuestner, P.
Subjects: Physics - Accelerator Physics
Abstract: A previous publication has shown that the in-plane polarization (IPP) component of a polarized 0.97-GeV/c deuteron beam in the COSY storage ring may acquire a polarization half-life in excess of 1000 s through a combination of beam bunching, electron cooling (prior to any spin manipulation), sextupole field adjustment, and a limitation of the beam intensity. This paper documents further tests pointing to additional gains in the IPP lifetime if cooling is active throughout the beam store., Comment: 11 pages, 6 figures Submitted to Physical Review Accelerators and Beams
Published: 2020
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11. Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study

Author: Abusaif, F., Aggarwal, A., Aksentev, A., Alberdi-Esuain, B., Andres, A., Atanasov, A., Barion, L., Basile, S., Berz, M., Böhme, C., Böker, J., Borburgh, J., Canale, N., Carli, C., Ciepał, I., Ciullo, G., Contalbrigo, M., De Conto, J. -M., Dymov, S., Felden, O., Gaisser, M., Gebel, R., Giese, N., Gooding, J., Grigoryev, K., Grzonka, D., Tahar, M. Haj, Hahnraths, T., Heberling, D., Hejny, V., Hetzel, J., Hölscher, D., Javakhishvili, O., Jorat, L., Kacharava, A., Kamerdzhiev, V., Karanth, S., Keshelashvili, I., Koop, I., Kulikov, A., Laihem, K., Lamont, M., Lehrach, A., Lenisa, P., Lomidze, I., Lomidze, N., Lorentz, B., Macharashvili, G., Magiera, A., Makino, K., Martin, S., Mchedlishvili, D., Meißner, U. -G., Metreveli, Z., Michaud, J., Müller, F., Nass, A., Natour, G., Nikolaev, N., Nogga, A., Okropiridze, D., Pesce, A., Poncza, V., Prasuhn, D., Pretz, J., Rathmann, F., Ritman, J., Rosenthal, M., Saleev, A., Schott, M., Sefzick, T., Senichev, Y., Shankar, R., Shergelashvili, D., Shmakova, V., Siddique, S., Silenko, A., Simon, M., Slim, J., Soltner, H., Stahl, A., Stassen, R., Stephenson, E., Straatmann, H., Ströher, H., Tabidze, M., Tagliente, G., Talman, R., Uzikov, Y., Valdau, Y., Valetov, E., Vilella, E., Vitz, M., Vossebeld, J., Wagner, T., Weidemann, C., Wirzba, A., Wrońska, A., Wüstner, P., Zupranski, P., and Żurek, M.
Subjects: High Energy Physics - Experiment, Nuclear Experiment, Physics - Accelerator Physics
Abstract: The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly $^3$He) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation from the longitudinal to the vertical direction. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. A stepwise plan is foreseen, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal plane polarization lifetimes, and control of the polarization direction through feedback from scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally a high-precision electric-field storage ring., Comment: 243 pages
Published: 2019
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12. Study of Three-Nucleon Dynamics in the dp breakup collisions using the WASA detector

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., Bondar, A., Buscher, M., Calen, H., Ciepal, I., Clement, H., Czerwinski, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Fohl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Heijkenskjold, L., Hejny, V., Husken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khoukaz, A., Khreptak, A., Kirillov, D. A., Kistryn, S., Kleines, H., Klos, B., Krzemien, W., Kulessa, P., Kupsc, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Morsch, H. -P., Moskal, P., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Ritman, J., Roy, A., Rundel, O., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Stroher, H., Szczurek, A., Trzcinski, A., Wolke, M., Wronska, A., Wustner, P., Yamamoto, A., Zabierowski, J., Zieli, M. J., Zlomanczuk, J., Zupranski, P., Zurek, M., Deltuva, A., Golak, J., Kozela, A., Skibinski, R., Skwira-Chalot, I., and Witala, H.
Subjects: Nuclear Experiment
Abstract: Differential cross section for the 1H(d,pp)n breakup reaction at deuteron beam energy of 340 MeV has been measured with the use of WASA detector at COSY-Juelich. The set of proton-proton coincidences registered at Forward Detector has been analysed on dense grid of kinematic variables, giving in total around 5600 data points. The cross section data are compared to theoretical predictions based on the state-of-the-art nucleon-nucleon potentials, combined with three-nucleon force, Coulomb interaction or carried out in a relativistic regime.
Published: 2019
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13. Search for eta mesic 3He with the WASA-at-COSY facility in the pd-> 3He 2gamma and pd-> 3He 6gamma reactions

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bass, S. D., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Heijkenskjöld, L., Hejny, V., Hirenzaki, S., Jarczyk, L., Johansson, T., Kamys, B., Kelkar, N. G., Kemmerling, G., Khreptak, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Morsch, H. P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Ritman, J., Roy, A., Rundel, O., Sawant, S., Schadmand, S., Schätti--Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: We report on the experimental search for the bound state of an $\eta$ meson and $^{3}\hspace{-0.03cm}\mbox{He}$ nucleus performed using the WASA-at-COSY detector setup. In order to search for the $\eta$-mesic nucleus decay, the $pd\rightarrow$ $^{3}\hspace{-0.03cm}\mbox{He} 2\gamma$ and $pd\rightarrow$ $^{3}\hspace{-0.03cm}\mbox{He} 6\gamma$ channels have been analysed. These reactions manifest the direct decay of $\eta$ meson bound in $^{3}\hspace{-0.03cm}\mbox{He}$ nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to an $^3$He-$\eta$ nucleus width $\Gamma$ above 20 MeV and binding energy $B_s$ between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the $\eta$-mesic $^{3}\hspace{-0.03cm}\mbox{He}$ nucleus formation followed by the $\eta$ meson decay which varies between $2$ nb and $15$ nb depending on possible bound state parameters., Comment: Article accepted to be published in PLB
Published: 2019
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14. Feasibility Study for an EDM Storage Ring

Author: Abusaif, F., Aggarwal, A., Aksentev, A., Alberdi-Esuain, B., Barion, L., Basile, S., Berz, M., Beyß, M., Böhme, C., Böker, J., Borburgh, J., Carli, C., Ciepał, I., Ciullo, G., Contalbrigo, M., De Conto, J. -M., Dymov, S., Engels, R., Felden, O., Gagoshidze, M., Gaisser, M., Gebel, R., Giese, N., Grigoryev, K., Grzonka, D., Hanraths, T., Hanhart, C., Heberling, D., Hejny, V., Hetzel, J., Hölscher, D., Javakhishvili, O., Kacharava, A., Karanth, S., Käseberg, C., Kamerdzhiev, V., Keshelashvili, I., Koop, I., Kulikov, A., Laihem, K., Lamont, M., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Macharashvili, G., Magiera, A., Maier, R., Makino, K., Martin, S., Mchedlishvili, D., Meißner, U. -G., Metreveli, Z., Michaud, J., Müller, F., Nass, A., Natour, G., Nikolaev, N., Nogga, A., Pesce, A., Poncza, V., Prasuhn, D., Pretz, J., Rathmann, F., Ritman, J., Rosenthal, M., Saleev, A., Schott, M., Sefzick, T., Senichev, Y., Shergelashvili, D., Shmakova, V., Siddique, S., Silenko, A., Simon, M., Slim, J., Soltner, H., Stahl, A., Stassen, R., Stephenson, E., Straatmann, H., Ströher, H., Tabidze, M., Tagliente, G., Tahar, M., Talman, R., Uzikov, Yu., Valdau, Yu., Valetov, E., Wagner, T., Weidemann, C., Wilkin, C., Wirzba, A., Wrońska, A., and Wüstner, P.
Subjects: Physics - Accelerator Physics, High Energy Physics - Experiment
Abstract: This project exploits charged particles confined as a storage ring beam (proton, deuteron, possibly $^3$He) to search for an intrinsic electric dipole moment (EDM, $\vec d$) aligned along the particle spin axis. Statistical sensitivities can approach $10^{-29}$~e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarization, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarization ($\vec d \times\vec E$). The slow rise in the vertical polarization component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal-plane polarization lifetimes, and control of the polarization direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring.
Published: 2018

15. Backward single-pion production in the $\boldsymbol{pd\rightarrow {}^3\textrm{He}\,\pi^0}$ reaction with WASA-at-COSY

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Morsch, H. --P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Złomańczuk, J., Żuprański, P., Żurek, M., and Wilkin, C.
Subjects: Nuclear Experiment, Nuclear Theory
Abstract: New data on the production of single neutral pions in the $pd\rightarrow{}^3\textrm{He}\,\pi^0$ reaction are presented. For fifteen proton beam momenta between $p_p=1.60\;\textrm{GeV}/c$ and $p_p=1.74\;\textrm{GeV}/c$, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum., Comment: 9 pages, 5 figures, 3 tables submitted to EPJA
Published: 2018
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16. On the Production of an Isotensor Dibaryon in the $pp \to pp\pi^+\pi^-$ Reaction

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Marciniewski, P., Mariański, B., Morsch, H. --P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti--Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p = 1.08 - 1.36$ GeV ($\sqrt s$ = 2.35 - 2.46 GeV), which includes the regions of $N^*(1440)$ and $\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with experimental differential cross sections and underpredict substantially the measured total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P) = 2(1^+)$ produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong and more recently calculated by Gal and Garcilazo.
Published: 2018
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17. An Isotensor Dibaryon in the $pp \to pp\pi^+\pi^-$ Reaction?

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Marciniewski, P., Mariański, B., Morsch, H. --P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti--Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have been carried out at WASA@COSY by means of $pd$ collisions at $T_p$ = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region $T_p = 1.08 - 1.36$ GeV, which is the region of $N^*(1440)$ and $\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor $\Delta N$ dibaryon resonance with $I(J^P) = 2(1^+)$ produced associatedly with a pion is able to overcome these deficiencies., Comment: arXiv admin note: substantial text overlap with arXiv:1803.03192
Published: 2018
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18. Search for $C$ violation in the decay $\eta\rightarrow\pi^0+e^++e^-$ with WASA-at-COSY

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Hanhart, C., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Morsch, H. -P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Złomańczuk, J., Żuprański, P., Żurek, M., and Wirzba, A.
Subjects: High Energy Physics - Experiment
Abstract: We report on the investigation of the rare decay $\eta\rightarrow\pi^0+\text{e}^++\text{e}^-$ which is of interest to study both $C$ violation in the electromagnetic interaction and to search for contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum J\"ulich, Germany. In total $3\times10^7$ events of the reaction $\text{p}+\text{d}\rightarrow{^3\text{He}}+\eta$ have been recorded at an excess energy of $Q = 59.8\,\textrm{MeV}$. Based on this data set the $C$ parity violating decay $\eta\rightarrow\pi^0+\gamma^*\rightarrow\pi^0+\textrm{e}^++\textrm{e}^-$ via a single-photon intermediate state has been searched for, resulting in new upper limits of $\Gamma\left(\eta\rightarrow\pi^0+\textrm{e}^++\textrm{e}^-\right)/ \Gamma\left(\eta\rightarrow\pi^++\pi^-+\pi^0\right) < 3.28\times10^{-5}$ and $\Gamma\left(\eta\rightarrow\pi^0+\textrm{e}^++\textrm{e}^-\right)/ \Gamma\left(\eta\rightarrow\textrm{all}\right) < 7.5\times10^{-6}\ (\textrm{CL} = 90\,\%)$, respectively., Comment: 7 pages, 8 figures, submitted to PLB
Published: 2018
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19. Total and differential cross sections of $\eta$-production in proton-deuteron fusion for excess energies between $Q_\eta=13\;\text{MeV}$ and $Q_\eta=81\;\text{MeV}$

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Hanhart, C., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Morsch, H. -P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawanta, S., Schadmand, S., Schätti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Złomańczuk, J., Żuprański, P., Żurek, M., and Wilkin, C.
Subjects: Nuclear Experiment, Nuclear Theory
Abstract: New data on both total and differential cross sections of the production of $\eta$ mesons in proton-deuteron fusion to ${}^3\text{He}\,\eta$ in the excess energy region $13.6\;\text{MeV}\leq Q_\eta \leq 80.9\;\text{MeV}$ are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum J\"ulich, using a proton beam at 15 different beam momenta between $p_p = 1.60\;\text{GeV}/c$ and $p_p = 1.74\;\text{GeV}/c$. While significant structure of the total cross section is observed in the energy region $20\;\text{MeV}\lesssim Q_\eta \lesssim 60\;\text{MeV}$, a previously reported sharp variation around $Q_\eta\approx 50\;\text{MeV}$ cannot be confirmed. Angular distributions show the typical forward-peaking that was reported elsewhere. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a large interval., Comment: 8 pages, 7 figures, preprint submitted to Physics Letters B
Published: 2018
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20. Phase Measurement for Driven Spin Oscillations in a Storage Ring

Author: Hempelmann, N., Hejny, V., Pretz, J., Soltner, H., Augustyniak, W., Bagdasarian, Z., Bai, M., Barion, L., Berz, M., Chekmenev, S., Ciullo, G., Dymov, S., Eversmann, D., Gaisser, M., Gebel, R., Grigoryev, K., Grzonka, D., Guidoboni, G., Heberling, D., Hetzel, J., Hinder, F., Kacharava, A., Kamerdzhiev, V., Keshelashvili, I., Koop, I., Kulikov, A., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Maanen, P., Macharashvili, G., Magiera, A., Mchedlishvili, D., Mey, S., Müller, F., Nass, A., Nikolaev, N. N., Nioradze, M., Pesce, A., Prasuhn, D., Rathmann, F., Rosenthal, M., Saleev, A., Schmidt, V., Semertzidis, Y., Shmakova, Y. Senichev V., Silenko, A., Slim, J., Stahl, A., Stassen, R., Stephenson, E., Stockhorst, H., Ströher, H., Tabidze, M., Tagliente, G., Talman, R., Engblom, P. Thörngren, Trinkel, F., Uzikov, Yu., Valdau, Yu., Valetov, E., Vassiliev, A., Weidemann, C., Wrońska, A., Wüstner, P., Zuprański, P., and Żurek, M.
Subjects: Physics - Accelerator Physics, 13.40.Em, 11.30.Er, 29.20.D, 29.20.dg, 29.20.db
Abstract: This paper reports the first simultaneous measurement of the horizontal and vertical components of the polarization vector in a storage ring under the influence of a radio frequency (rf) solenoid. The experiments were performed at the Cooler Synchrotron COSY in J\"ulich using a vector polarized, bunched $0.97\,\textrm{GeV/c}$ deuteron beam. Using the new spin feedback system, we set the initial phase difference between the solenoid field and the precession of the polarization vector to a predefined value. The feedback system was then switched off, allowing the phase difference to change over time, and the solenoid was switched on to rotate the polarization vector. We observed an oscillation of the vertical polarization component and the phase difference. The oscillations can be described using an analytical model. The results of this experiment also apply to other rf devices with horizontal magnetic fields, such as Wien filters. The precise manipulation of particle spins in storage rings is a prerequisite for measuring the electric dipole moment (EDM) of charged particles.
Published: 2018
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21. The connection between zero chromaticity and long in-plane polarization lifetime in a magnetic storage ring

Author: Guidoboni, G., Stephenson, E. J., Wrońska, A, Bagdasarian, Z., Bsaisou, J., Chekmenev, S., Dymov, S., Eversmann, D., Gaisser, M., Gebel, R., Hejny, V., Hempelmann, N., Hinder, F., Kacharava, A., Keshelashvili, I., Kulessa, P., Lenisa, P., Lehrach, A., Lorentz, B., Maanen, P., Maier, R., Mchedlishvili, D., Mey, S., Nass, A., Pesce, A., Orlov, Y., Pretz, J., Prasuhn, D., Rathmann, F., Rosenthal, M., Saleev, A., Semertzidis, Y. K., Senichev, Y., Shmakova, V., Stockhorst, H., Ströher, H., Talman, R., Thörngren-Engblom, P., Trinkel, F., Valdau, Yu., Weidemann, C., Wüstner, P., and Zyusin, D.
Subjects: Physics - Accelerator Physics, Nuclear Experiment, Physics - Instrumentation and Detectors
Abstract: In this paper, we demonstrate the connection between a magnetic storage ring with additional sextupole fields set so that the x and y chromaticities vanish and the maximizing of the lifetime of in-plane polarization (IPP) for a 0.97-GeV/c deuteron beam. The IPP magnitude was measured by continuously monitoring the down-up scattering asymmetry (sensitive to sideways polarization) in an in-beam, carbon-target polarimeter and unfolding the precession of the IPP due to the magnetic anomaly of the deuteron. The optimum operating conditions for a long IPP lifetime were made by scanning the field of the storage ring sextupole magnet families while observing the rate of IPP loss during storage of the beam. The beam was bunched and electron cooled. The IPP losses appear to arise from the change of the orbit circumference, and consequently the particle speed and spin tune, due to the transverse betatron oscillations of individual particles in the beam. The effects of these changes are canceled by an appropriate sextupole field setting., Comment: 18 pages, 18 figures, prepared for Phys. Rev. Accel. Beams
Published: 2017
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22. Spin dependence of {\eta} meson production in proton-proton collisions close to threshold

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bass, S. D., Bergmann, F. S., Berlowski, M., Bondar, A., Buscher, M., Calen, H., Ciepal, I., Clement, H., Czerwinski, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Fohl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullstrom, C. -O., Heijkenskjold, L., Hejny, V., Husken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Klos, B., Krzemien, W., Kulessa, P., Kupsc, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Morsch, H. -P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schatti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Szczurek, H. Stroher A., Trzcinski, A., Wolke, M., Wronska, A., Wustner, P., Yamamoto, A., Zabierowski, J., Zielinski, M. J., Zlomanczuk, J., Zupranski, P., and Zurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment, High Energy Physics - Phenomenology, Nuclear Theory
Abstract: Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high degree of the polarized proton beam of COSY, the reaction pp{\to} pp{\eta} has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the precision improved by more than one order of magnitude with respect to previous results allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q = 15 MeV signaling s wave production with no evidence for higher partial waves. At Q = 72 MeV the data reveals strong interference of P s and P p partial waves and cancellation of (P p) and Ss*Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the {\eta} meson., Comment: Accepted for publication in Phys. Rev. Lett
Published: 2017
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23. Importance of d-wave contributions in the charge symmetry breaking reaction $dd \to {}^4\text{He}\pi^0$

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Hanhart, C., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Morsch, H. -P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction $dd \to {}^4\text{He}\pi^0$ using the WASA-at-COSY detector setup at an excess energy of $Q = 60$ MeV. The determined differential cross section can be parametrized as $\text{d}\sigma/\text{d}\Omega = a + b\cos^{2}\theta^*$, where $\theta^*$ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are $a = \left(1.55 \pm 0.46 (\text{stat}) ^{+0.32}_{-0.8} (\text{syst}) \right)$ pb/sr and $b = \left(13.1 \pm 2.1 (\text{stat}) ^{+1.0}_{-2.7} (\text{syst})\right)$ pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the $\Delta$ isobar to the $dd \to {}^4\text{He}\pi^0$ reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions., Comment: 5 figures
Published: 2017
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24. Phase locking the spin precession in a storage ring

Author: Hempelmann, N., Hejny, V., Pretz, J., Stephenson, E., Augustyniak, W., Bagdasarian, Z., Bai, M., Barion, L., Berz, M., Chekmenev, S., Ciullo, G., Dymov, S., Etzkorn, F. -J., Eversmann, D., Gaisser, M., Gebel, R., Grigoryev, K., Grzonka, D., Guidoboni, G., Hanraths, T., Heberling, D., Hetzel, J., Hinder, F., Kacharava, A., Kamerdzhiev, V., Keshelashvili, I., Koop, I., Kulikov, A., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Maanen, P., Macharashvili, G., Magiera, A., Mchedlishvili, D., Mey, S., Müller, F., Nass, A., Nikolaev, N. N., Pesce, A., Prasuhn, D., Rathmann, F., Rosenthal, M., Saleev, A., Schmidt, V., Semertzidis, Y., Shmakova, V., Silenko, A., Slim, J., Soltner, H., Stahl, A., Stassen, R., Stockhorst, H., Ströher, H., Tabidze, M., Tagliente, G., Talman, R., Engblom, P. Thörngren, Trinkel, F., Uzikov, Yu., Valdau, Yu., Valetov, E., Vassiliev, A., Weidemann, C., Wrońska, A., Wüstner, P., Zuprański, P., and Żurek, M.
Subjects: Physics - Accelerator Physics
Abstract: This letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV/$c$ bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring in order to control both the precession rate ($\approx 121$ kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a one standard deviation range of $\sigma = 0.21$ rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.
Published: 2017
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25. Spin tune mapping as a novel tool to probe the spin dynamics in storage rings

Author: Saleev, A., Nikolaev, N. N., Rathmann, F., Augustyniak, W., Bagdasarian, Z., Bai, M., Berz, M., Chekmenev, S., Ciullo, G., Dymov, S., Eversmann, D., Gaisser, M., Gebel, R., Grigoryev, K., Grzonka, D., Guidoboni, G., Heberling, D., Hempelmann, N., Hejny, V., Hetzel, J., Hinder, F., Kacharava, A., Kamerdzhiev, V., Keshelashvili, I., Koop, I., Kulikov, A., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Maanen, P., Macharashvili, G., Mchedlishvili, D., Magiera, A., Mey, S., Nass, A., Pesce, A., Prasuhn, D., Pretz, J., Rosenthal, M., Schmidt, V., Semertzidis, Y., Senichev, Y., Shmakova, V., Silenko, A., Slim, J., Stahl, A., Stassen, R., Stephenson, E., Stockhorst, H., Ströher, H., Engblom, P. Thörngren, Tabidze, M., Tagliente, G., Talman, R., Trinkel, F., Uzikov, Yu., Valdau, Yu., Valetov, E., Vassiliev, A., Weidemann, C., Wrońska, A., Wüstner, P., and Zuprański, P.
Subjects: Physics - Accelerator Physics, Nuclear Experiment, Physics - Instrumentation and Detectors
Abstract: Precision experiments, such as the search for electric dipole moments of charged particles using storage rings, demand for an understanding of the spin dynamics with unprecedented accuracy. The ultimate aim is to measure the electric dipole moments with a sensitivity up to 15 orders in magnitude better than the magnetic dipole moment of the stored particles. This formidable task requires an understanding of the background to the signal of the electric dipole from rotations of the spins in the spurious magnetic fields of a storage ring. One of the observables, especially sensitive to the imperfection magnetic fields in the ring is the angular orientation of stable spin axis. Up to now, the stable spin axis has never been determined experimentally, and in addition, the JEDI collaboration for the first time succeeded to quantify the background signals that stem from false rotations of the magnetic dipole moments in the horizontal and longitudinal imperfection magnetic fields of the storage ring. To this end, we developed a new method based on the spin tune response of a machine to artificially applied longitudinal magnetic fields. This novel technique, called \textit{spin tune mapping}, emerges as a very powerful tool to probe the spin dynamics in storage rings. The technique was experimentally tested in 2014 at the cooler synchrotron COSY, and for the first time, the angular orientation of the stable spin axis at two different locations in the ring has been determined to an unprecedented accuracy of better than $2.8\mu$rad., Comment: 32 pages, 15 figures, 7 tables
Published: 2017
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26. Isoscalar Single-Pion Production in the Region of Roper and $d^*(2380)$ Resonances

Author: Collaboration, WASA-at-COSY, Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calen, H., Ciepał, I., Clement, H., Czerwinski, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Grigoryev, A. Goswami K., Gullström, C. -O., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemien, W., Kulessa, P., Kupsc, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Morsch, H. -P., Moskal, P., Ohm, H., Parol, W., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzcinski, A., Varma, R., Wolke, M., Wronska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zielinski, M. J., Złomanczuk, J., Zupranski, P., and Zurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Exclusive measurements of the quasi-free $pn \to pp\pi^-$ and $pp \to pp\pi^0$ reactions have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p = 0.95 - 1.3$ GeV ($\sqrt s$ = 2.3 - 2.46 GeV), which includes the regions of $\Delta(1232)$, $N^*(1440)$ and $d^*(2380)$ resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below $T_p$ = 1 GeV. We observe a substantial increase of this cross section above 1 GeV, which can be related to the Roper resonance $N^*(1440)$, the strength of which shows up isolated from the $\Delta$ resonance in the isoscalar $(N\pi)_{I=0}$ invariant-mass spectrum. No evidence for a decay of the dibaryon resonance $d^*(2380)$ into the isoscalar $(NN\pi)_{I=0}$ channel is found. An upper limit of 90 $\mu$b (90 $\%$ C.L.) corresponding to a branching ratio of 5 $\%$ has been deduced., Comment: erratum: the upper limit for the branching ratio of the decay $d^*(2380) \to (NN\pi)_{I=0}$ is a factor of two smaller than given in the previous version of this article
Published: 2017

27. Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., Bhatt, H., Bondar, A., Buescher, 9 M., Calen, H., Ciepal, I., Clement, H., Czerwinski, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Foehl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullstroem, C. -O., Heijkenskjoeld, L., Hejny, V., Huesken, N., Jarczyk, L., Johansson, T., Kamys, B., Kelkar, N. G., Kemmerling, G., Khatri, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Klos, B., Krzemien, W., Kulessa, P., Kupsc, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Morsch, H. -P., Moskal, P., Ohm, H., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schaetti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Stroeher, H., Szczurek, A., Trzcinski, A., Varma, R., Wolke, M., Wronska, A., Wuestner, P., Yamamoto, A., Zabierowski, J., Zielinski, M. J., Zlomanczuk, J., Zupranski, P., and Zurek, M.
Subjects: Nuclear Experiment
Abstract: The search for 4He-eta bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the dd->3He n pi0 and dd->3He p pi- processes. The beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd->4He eta reaction ranging from Q=-70 MeV to Q=30 MeV. The luminosity was determined based on the dd->3He n reaction and quasi-free proton-proton scattering via dd->pp n_spectator n_spectator reactions. The excitation functions determined independently for the measured reactions do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in dd->(4He-eta)_bound->3He n pi0 and dd->(4He-eta)_bound->3He p pi- processes were determined taking into account the isospin relation between both the channels considered. The results of the analysis depend on the assumptions of the N* momentum distribution in the anticipated mesic-4He. Assuming as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in 4He, we determined that (for the mesic bound state width in the range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for npi0 and ppi- channels, respectively. However, based on the recent theoretical findings of the N*(1535) momentum distribution in the N*-3He nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for npi0 and ppi- channels respectively., Comment: This article will be submitted to JHEP
Published: 2016
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28. Measurement of the $\omega \to \pi^+ \pi^- \pi^0$ Dalitz plot distribution

Author: Collaboration, The WASA-at-COSY, Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khatri, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Morsch, H. -P., Moskal, P., Ohm, H., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Trzciński, A., Varma, R., Wolke, M., Wrońska, A., Wüstner, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Złomańczuk, J., Żuprański, P., Żurek, M., Kubis, B., and Leupold, S.
Subjects: Nuclear Experiment
Abstract: Using the production reactions $pd\to {}^3\mbox{He}\,\omega$ and $pp\to pp\omega$, the Dalitz plot distribution for the $\omega \to \pi^+ \pi^- \pi^0$ decay is studied with the WASA detector at COSY, based on a combined data sample of $ (4.408\pm 0.042) \times 10^4$ events. The Dalitz plot density is parametrised by a product of the $P$-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables $Z$ and $\phi$. For the first time, a deviation from pure $P$-wave phase space is observed with a significance of $4.1\sigma$. The deviation is parametrised by a linear term $1+2\alpha Z$, with $\alpha$ determined to be $+0.147\pm0.036$, consistent with the expectations of $\rho$-meson-type final-state interactions of the $P$-wave pion pairs., Comment: 8 pages, 7 figures
Published: 2016
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29. Search for an Isospin I =3 Dibaryon

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., Bhatt, H., Bondar, A., Buescher, M., Calen, H., Ciepa, I., Clement, H., Czerwinski, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Foehl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullstroem, C. -O., Heijkenskjoeld, L., Hejny, V., Huesken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khatri, G., Khoukaz, A., Khreptak, O., Kirillov, D. A., Kistryn, S., Kleines, H., Klos, B., Krzemien, W., Kulessa, P., Kupsc, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Morsch, H. -P., Moskal, P., Ohm, H., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pysniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schaetti-Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Strassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Stroeher, H., Szczurek, A., Trzcinski, A., Varma, R., Wolke, M., Wronska, A., Wuestner, P., Yamamoto, A., Zabierowski, J., Zielinski, M. J., Zink, A., Zlomanczuk, J., Zupranski, P., and Zurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance $d^*(2380)$ with $I(J^P) = 0(3^+)$ there should also exist a dibaryon resonance with mirrored quantum numbers $I(J^P) = 3(0^+)$. We report here on a search for such a $NN$-decoupled state in data on the $pp \to pp\pi^+\pi^+\pi^-\pi^-$ reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280 - 2500 MeV.
Published: 2016
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30. Measurement of the $\vec{n}p \to d\pi^0\pi^0$ Reaction with Polarized Beam in the Region of the $d^*(2380)$ Resonance

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calen, H., Ciepał, I., Clement, H., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khatri, G., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lawani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, . P., Mariański, B., Morsch, H. -P., Moskal, P., Ohm, H., del Rio, E. Perez, Piskunov, N. M., Prashun, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Schätti--Ozerianska, I., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wolke, M., Wrońska, A., Wüstner, P., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: We report on a high-statistics measurement of the most basic double pionic fusion reaction $\vec{n}p \to d\pi^0\pi^0$ over the energy region of the $d^*(2380)$ resonance by use of a polarized deuteron beam and observing the double fusion reaction in the quasifree scattering mode. The measurements were performed with the WASA detector setup at COSY. The data reveal substantial analyzing powers and confirm conclusions about the $d^*$ resonance obtained from unpolarized measurements. We also confirm the previous unpolarized data obtained under complementary kinematic conditions.
Published: 2016
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31. Measurements of Branching Ratios for $\eta$ Decays into Charged Particles

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goswami, A., Grigoryev, K., Gullström, C. -O., Heijkenskjöld, L., Hejny, V., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khatri, G., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Prasuhn, D., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Rundel, O., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Sitterberg, K., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wiedner, U., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: The WASA-at-COSY experiment has collected $3\times10^{7}$ events with $\eta$-mesons produced via the reaction $pd\rightarrow{^{3}\textrm{He}}\eta$ at $\textrm{T} = 1.0 \textrm{GeV}$. Using this data set, we evaluate the branching ratios of the decays $\eta\to\pi^{+}\pi^{-}\gamma$, $\eta\to e^{+}e^{-}\gamma$, $\eta\to\pi^{+}\pi^{-}e^{+}e^{-}$ and $\eta\to e^{+}e^{-}e^{+}e^{-}$. The branching ratios are normalized to the $\eta\rightarrow\pi^{+}\pi^{-}\pi^{0}$ decay. In addition an upper limit on a $CP$-violating asymmetry in $\eta\rightarrow \pi^{+}\pi^{-}e^{+}e^{-}$ is extracted.
Published: 2015
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32. Kaon pair production in proton-nucleus collisions at 2.83 GeV kinetic energy

Author: Kiselev, Yu. T., Hartmann, M., Polyanskiy, A., Paryev, E. Ya., Barsov, S., Buescher, M., Dymov, S., Gebel, R., Hejny, V., Kacharava, A., Keshelashvili, I., Lorentz, B., Maeda, Y., Merzliakov, S., Mikirtytchiants, S., Ohm, H., Serdyuk, V., Sibirtsev, A., Sinitsyna, V. Y., Stein, H. J., Stroeher, H., Trusov, S., Valdau, Yu., Wilkin, C., Wuestner, P., and Ye, Q. J.
Subjects: Nuclear Experiment, Nuclear Theory
Abstract: The production of non-phi K+K- pairs by protons of 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets has been investigated using the COSY-ANKE magnetic spectrometer. The K- momentum dependence of the differential cross section has been measured at small angles over the 0.2--0.9 GeV/c range. The comparison of the data with detailed model calculations indicates an attractive K- -nucleus potential of about -60 MeV at normal nuclear matter density at a mean momentum of 0.5 GeV/c. However, this approach has difficulty in reproducing the smallness of the observed cross sections at low K- momenta., Comment: 7 pages, 5 figures, 1 table
Published: 2015
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33. New method for a continuous determination of the spin tune in storage rings and implications for precision experiments

Author: Eversmann, D., Hejny, V., Hinder, F., Kacharava, A., Pretz, J., Rathmann, F., Rosenthal, M., Trinkel, F., Andrianov, S., Augustyniak, W., Bagdasarian, Z., Bai, M., Bernreuther, W., Bertelli, S., Berz, M., Bsaisou, J., Chekmenev, S., Chiladze, D., Ciullo, G., Contalbrigo, M., de Vries, J., Dymov, S., Engels, R., Esser, F. M., Felden, O., Gaisser, M., Gebel, R., Glückler, H., Goldenbaum, F., Grigoryev, K., Grzonka, D., Guidoboni, G., Hanhart, C., Heberling, D., Hempelmann, N., Hetzel, J., Hipple, R., Hölscher, D., Ivanov, A., Kamerdzhiev, V., Kamys, B., Keshelashvili, I., Khoukaz, A., Koop, I., Krause, H-J., Krewald, S., Kulikov, A., Lehrach, A., Lenisa, P., Lomidze, N., Lorentz, B., Maanen, P., Macharashvili, G., Magiera, A., Maier, R., Makino, K., Marianski, B., Mchedlishvili, D., Meißner, Ulf-G., Mey, S., Nass, A., Natour, G., Nikolaev, N., Nioradze, M., Nogga, A., Nowakowski, K., Pesce, A., Prasuhn, D., Ritman, J., Rudy, Z., Saleev, A., Semertzidis, Y., Senichev, Y., Shmakova, V., Silenko, A., Slim, J., Soltner, H., Stahl, A., Stassen, R., Statera, M., Stephenson, E., Stockhorst, H., Straatmann, H., Ströher, H., Tabidze, M., Talman, R., Engblom, P. Thörngren, Trzcinski, A., Uzikov, Yu., Valdau, Yu., Valetov, E., Vassiliev, A., Weidemann, C., Wilkin, C., Wirzba, A., Wronska, A., Wüstner, P., Zakrzewska, M., Zaplatin, E., Zupranski, P., and Zyuzin, D.
Subjects: Physics - Accelerator Physics, Nuclear Experiment
Abstract: A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune - defined as the number of spin precessions per turn - is given by $\nu_s = \gamma G$ (gamma is the Lorentz factor, $G$ the magnetic anomaly). For 970 MeV/c deuterons coherently precessing with a frequency of ~120 kHz in the Cooler Synchrotron COSY, the spin tune is deduced from the up-down asymmetry of deuteron carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order $10^{-8}$, and to $1 \cdot 10^{-10}$ for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics: controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring., Comment: 6 pages, 6 figures
Published: 2015
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34. Measurement of the $np \to np\pi^0\pi^0$ Reaction in Search for the Recently Observed $d^*(2380)$ Resonance

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. --O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Höistad, B., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wagner, G. J., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: Exclusive measurements of the quasi-free $np \to np\pi^0\pi^0$ reaction have been performed by means of $dp$ collisions at $T_d$ = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $\sqrt s$ = (2.35 - 2.46) GeV, which includes the region of the ABC effect and its associated $d^*(2380)$ resonance. Adding the $d^*$ resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of F\"aldt and Wilkin as well Albadajedo and Oset. The ABC effect, {\it i.e.} the low-mass enhancement in the $\pi^0\pi^0$-invariant mass spectrum, is found to be very modest - if present at all, which might pose a problem to some of its interpretations.
Published: 2014
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35. ABC Effect and Resonance Structure in the Double-Pionic Fusion to $^3$He

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. --O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Höistad, B., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wagner, G. J., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yurev, L., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Exclusive and kinematically complete measurements of the double pionic fusion to $^3$He have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the $\pi\pi$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observations in the basic $pn \to d \pi^0\pi^0$ reaction and in the $dd \to ^4$He$\pi^0\pi^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of $d^*$ resonance formation during the reaction process in addition to the conventional $t$-channel $\Delta\Delta$ mechanism. The deduced $d^*$ resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.
Published: 2014
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36. Neutron-Proton Scattering in the Context of the $d^*$(2380) Resonance

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. --O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hodana, M., Höistad, B., Hüsken, N., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krapp, M., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wagner, G. J., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yurev, L., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., {Ż}uprański, P., {Ż}urek, M., Workman, R. L., Briscoe, W. J., and Strakovsky, I. I.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: New data on quasifree polarized neutron-proton scattering, in the region of the recently observed $d^*$ resonance structure, have been obtained by exclusive and kinematically complete high-statistics measurements with WASA at COSY. This paper details the determination of the beam polarization, checks of the quasifree character of the scattering process, on all obtained $A_y$ angular distributions and on the new partial-wave analysis, which includes the new data producing a resonance pole in the $^3D_3$-$^3G_3$ coupled partial waves at ($2380\pm10 - i40\pm5$) MeV -- in accordance with the $d^*$ dibaryon resonance hypothesis. The effect of the new partial-wave solution on the description of total and differential cross section data as well as specific combinations of spin-correlation and spin-transfer observables available from COSY-ANKE measurements at $T_d$ = 2.27 GeV is discussed.
Published: 2014
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37. Charge Symmetry Breaking in dd->4He{\pi}0 with WASA-at-COSY

Author: Collaboration, WASA-at-COSY, Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. -O., Hanhart, C., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Höistad, B., Hüsken, N., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yurev, L., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd->4He{\pi}0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of p=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to sigma(tot) = (118 +- 18(stat) +- 13(sys) +- 8(ext)) pb and first data on the differential cross section are consistent with s-wave pion production., Comment: 14 pages, 5 figures
Published: 2014
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38. Measurement of the $\eta\to\pi^+\pi^-\pi^0$ Dalitz plot distribution

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. -O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hodana, M., Höistad, B., Hüsken, N., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kleines, H., Kłos, B., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Martemyanov, B. V., Meißner, U. -G., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Shwartz, B., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: Dalitz plot distribution of the $\eta\to\pi^+\pi^-\pi^0$ decay is determined using a data sample of $1.2\cdot 10^7$ $\eta$ mesons from $pd\to ^3\textrm{He}\eta$ reaction at 1 GeV collected by the WASA detector at COSY., Comment: 13 pages, 6 figures
Published: 2014
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39. Measuring the Polarization of a Rapidly Precessing Deuteron Beam

Author: Bagdasarian, Z., Bertelli, S., Chiladze, D., Ciullo, G., Dietrich, J., Dymov, S., Eversmann, D., Fanourakis, G., Gaisser, M., Gebel, R., Gou, B., Guidoboni, G., Hejny, V., Kacharava, A., Kamerdzhiev, V., Lehrach, A., Lenisa, P., Lorentz, B., Magallanes, L., Maier, R., Mchedlishvili, D., Morse, W. M., Nass, A., Oellers, D., Pesce, A., Prasuhn, D., Pretz, J., Rathmann, F., Shmakova, V., Semertzidis, Y. K., Stephenson, E. J., Stockhorst, H., Ströher, H., Talman, R., Engblom, P. Thörngren, Valdau, Yu., Weidemann, C., and Wüstner, P.
Subjects: Physics - Accelerator Physics
Abstract: This paper describes a time-marking system that enables a measurement of the in-plane (horizontal) polarization of a 0.97-GeV/c deuteron beam circulating in the Cooler Synchrotron (COSY) at the Forschungszentrum J\"ulich. The clock time of each polarimeter event is used to unfold the 120-kHz spin precession and assign events to bins according to the direction of the horizontal polarization. After accumulation for one or more seconds, the down-up scattering asymmetry can be calculated for each direction and matched to a sinusoidal function whose magnitude is proportional to the horizontal polarization. This requires prior knowledge of the spin tune or polarization precession rate. An initial estimate is refined by re-sorting the events as the spin tune is adjusted across a narrow range and searching for the maximum polarization magnitude. The result is biased toward polarization values that are too large, in part because of statistical fluctuations but also because sinusoidal fits to even random data will produce sizeable magnitudes when the phase is left free to vary. An analysis procedure is described that matches the time dependence of the horizontal polarization to templates based on emittance-driven polarization loss while correcting for the positive bias. This information will be used to study ways to extend the horizontal polarization lifetime by correcting spin tune spread using ring sextupole fields and thereby to support the feasibility of searching for an intrinsic electric dipole moment using polarized beams in a storage ring. This paper is a combined effort of the Storage Ring EDM Collaboration and the JEDI Collaboration., Comment: 28 pages, 15 figures, prepared for Physical Review ST - Accelerators and Beams
Published: 2014
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40. Evidence for a New Resonance from Polarized Neutron-Proton Scattering

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berlowski, M., Bhatt, H., Buescher, M., Ciepa, H. Calen. I., Clement, H., Coderre, D., Czerwinski, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Foehl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoyev, K., Gullstroem, C. -O., Hauenstein, F., Heijkenskjoeld, L., Hejny, V., Hodana, M., Hoistad, B., Huesken, N., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirrilov, D. A., Kistryn, S., Kleines, H., Klos, B., Krapp, M., Krzemien, W., Kulessa, P., Kupsc, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Podkopal, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pysniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Stroeher, H., Szczurek, A., Taeschner, A., Trzcinski, A., Varma, R., Wagner, G. J., Wolke, M., Wronska, A., Wuestner, P., Wurm, P., Yamamoto, A., Yurev, L., Zabierowski, J., Zielinski, M. J., Zink, A., Zlomanczuk, J., Zupranski, P., Zurek, M., Workman, R. L., Briscoe, W. J., and Strakovsky, I. I.
Subjects: Nuclear Experiment
Abstract: Exclusive and kinematically complete high-statistics measurements of quasifree polarized $\vec{n}p$ scattering have been performed in the energy region of the narrow resonance structure $d^*$ with $I(J^P) = 0(3^+)$, $M \approx$ 2380 MeV/$c^2$ and $\Gamma \approx$ 70 MeV observed recently in the double-pionic fusion channels $pn \to d\pi^0\pi^0$ and $pn \to d\pi^+\pi^-$. The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process $\vec{d}p \to np + p_{spectator}$. That way the $np$ analyzing power $A_y$ was measured over a large angular range. The obtained $A_y$ angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new $A_y$ data into the SAID analysis produces a pole in the $^3D_3 - ^3G_3$ waves as expected from the $d^*$ resonance hypothesis.
Published: 2014
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41. Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, A., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. -O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hodana, M., Höistad, B., Hüsken, N., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Kłos, B., Kleines, H., Krapp, M., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Ohm, H., Ozerianska, I., Passfeld, A., del Rio, E. Perez, Piskunov, N. M., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Sefzick, T., Serdyuk, V., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Trzciński, A., Varma, R., Wagner, G. J., Węglorz, W., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yurev, L., Zabierowski, J., Zieliński, M. J., Zink, A., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: We present new data for angular distributions and on the cross section ratio of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval., Comment: 9 pages, 9 figures
Published: 2014
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42. MesonNet 2013 International Workshop. Mini-proceedings

Author: Amaryan, M. J., Bashkanov, M., Benayoun, M., Bergmann, F., Bijnens, J., Balkestahl, L. Caldeira, Clement, H., Colangelo, G., Daub, J., Eidelman, S., Fang, S., Gajos, A., Giovannella, S., Goudzovski, E., Grzonka, D., Gullström, C. O., Gumberidze, M., Heijkenskjöld, L., Hejny, V., Hoferichter, M., Husek, T., Ikeno, N., Ivashyn, S., Johansson, T., Kadavý, T., Kampf, K., Kolesár, M., Kupsc, A., Lang, M., Lorenz, M., Lutz, M. F. M., Machner, H., Masjuan, P., Metag, V., Moussallam, B., Nagahiro, H., Nanova, M., Niecknig, F., Papenbrock, M., Peña, M. T., Pettersson, J., Longhi, I. Prado, Prencipe, E., Balwierz-Pytko, I., Przygoda, W., Redmer, C. F., Sarra, I., Sawant, S., Schneider, S. P., Shwartz, B., Skurzok, M., Tanaka, Y. K., Terschlüsen, C., Unverzagt, M., Yamagata-Sekihara, J., Zdráhal, M., and Zétényi, M.
Subjects: High Energy Physics - Phenomenology, High Energy Physics - Experiment, Nuclear Experiment, Nuclear Theory
Abstract: The mini-proceedings of the MesonNet 2013 International Workshop held in Prague from June 17th to 19th, 2013, are presented. MesonNet is a research network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of the conference, which contains all talks, can be found at http://ipnp.mff.cuni.cz/mesonnet13, Comment: 106 pages, 53 contributions. Mini-proceedings of the MesonNet 2013 International Workshop. Editors: K. Kampf, A. Kupsc, and P. Masjuan
Published: 2013

43. Measurement of the $pn \to pp\pi^0\pi^-$ Reaction in Search for the Recently Observed Resonance Structure in $d\pi^0\pi^0$ and $d\pi^+\pi^-$ systems

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. --O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hinterberger, F., Hodana, M., Höistad, B., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Klaja, J., Kleines, H., Kłos, B., Krapp, M., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Li, L., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Nandi, B. K., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Pluciński, P., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schmidt, A., Schadmand, S., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Tolba, T., Trzciński, A., Varma, R., Wagner, G. J., Węglorz, W., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yuan, X., Zabierowski, J., Zheng, C., Zieliński, M. J., Zipper, W., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: Exclusive measurements of the quasi-free $pn \to pp\pi^0\pi^-$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $\sqrt s$ = (2.35 - 2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. No ABC effect, {\it i.e.} low-mass enhancement is found in the $\pi^0\pi^-$-invariant mass spectrum -- in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative s-wave. At the upper end of the covered energy region $t$-channel processes for Roper, $\Delta(1600)$ and $\Delta\Delta$ excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at $m$=~2.37 GeV with $\Gamma$ =~70 MeV and $I(J^P)=~0(3^+)$ observed recently in $pn \to d\pi^0\pi^0$ and $pn \to d\pi^+\pi^-$ reactions leads to an agreement with the data also at low energies.
Published: 2013
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44. Investigation of the dd -> 3He n \pi 0 reaction with the FZ J\'ulich WASA-at-COSY facility

Author: Collaboration, WASA-at-COSY, Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. --O., Hanhart, C., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hinterberger, F., Hodana, M., Höistad, B., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kirillov, D. A., Kistryn, S., Klaja, J., Kleines, H., Kłos, B., Krapp, M., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lersch, D., Li, L., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Nandi, B. K., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N. M., Pluciński, P., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schmidt, A., Schadmand, S., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Tolba, T., Trzciński, A., Varma, R., Wagner, G. J., Węglorz, W., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yuan, X., Zabierowski, J., Zheng, C., Zieliński, M. J., Zipper, W., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: Nuclear Experiment
Abstract: An exclusive measurement of the dd -> 3He n \pi 0 reaction was carried at a beam momentum of p = 1.2 GeV/c using the WASA-at-COSY facility. For the first time data on the total cross section as well as differential distributions were obtained. The data are described with a phenomenological approach based on a combination of a quasi-free model and a partial wave expansion for three-body reaction. The total cross section is found to be \sigma(tot) = (2.89 +- 0.01(stat) +- 0.06(sys) +- 0.29(norm)) \mu b. The contribution of the quasi-free processes (with the neutron being target or beam spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of the phase space. The remaining part of the cross section can be described within a partial wave decomposition indicating the significance of p-wave contributions in the final state., Comment: 9 pages, 7 figures
Published: 2013
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45. Search for a dark photon in the $\pi^0 \to e^+e^-\gamma$ decay

Author: Collaboration, WASA-at-COSY, Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bergmann, F. S., Berłowski, M., Bhatt, H., Bondar, A., Büscher, M., Calén, H., Ciepał, I., Clement, H., Coderre, D., Czerwiński, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullström, C. -O., Hauenstein, F., Heijkenskjöld, L., Hejny, V., Hinterberger, F., Hodana, M., Höistad, B., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Kłos, B., Krapp, M., Krzemień, W., Kulessa, P., Kupść, A., Kuzmin, A., Lalwani, K., Lersch, D., Li, L., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Mariański, B., Meißner, U. -G., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Nandi, B. K., Ohm, H., Ozerianska, I., del Rio, E. Perez, Piskunov, N., Pluciński, P., Podkopał, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Schmidt, A., Sefzick, T., Serdyuk, V., Shah, N., Shwartz, B., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Tolba, T., Trzciński, A., Varma, R., Wagner, G. J., Wȩglorz, W., Wirzba, A., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yamamoto, A., Zabierowski, J., Zieliński, M. J., Zipper, W., Złomańczuk, J., Żuprański, P., and Żurek, M.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology, Nuclear Experiment
Abstract: The presently world largest data sample of pi0 --> gamma e+e- decays containing nearly 5E5 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi0 --> gamma U --> gamma e+e- decay from the pp-->pp\pi^0 reaction was carried out. An upper limit on the square of the U-gamma mixing strength parameter epsilon^2 of 5e-6 at 90% CL was obtained for the mass range 20 MeV
Published: 2013
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46. The production of K+K- pairs in proton-proton collisions below the phi meson threshold

Author: Ye, Q. J., Hartmann, M., Chiladze, D., Dymov, S., Dzyuba, A., Gao, H., Gebel, R., Hejny, V., Kacharava, A., Lorentz, B., Mchedlishvili, D., Merzliakov, S., Mielke, M., Mikirtytchiants, S., Ohm, H., Papenbrock, M., Polyanskiy, A., Serdyuk, V., Stein, H. J., Stroeher, H., Trusov, S., Valdau, Yu., Wilkin, C., and Wuestner, P.
Subjects: Nuclear Experiment
Abstract: The pp -> ppK+K- reaction was measured below the phi threshold at a beam energy of 2.568 GeV using the COSY-ANKE magnetic spectrometer. By assuming that the four-body phase space is distorted only by the product of two-body final state interactions, fits to a variety of one-dimensional distributions permit the evaluation of differential and total cross sections. The shapes of the distributions in the Kp and Kpp invariant masses are reproduced only if the K-p interaction is even stronger than that found at higher energy. The cusp effect in the K+K- distribution at the K0K0bar threshold is much more clear and some evidence is also found for coupling between the K-p and K0bar n channels. However, the energy dependence of the total cross section cannot be reproduced by considering only a simple product of such pair-wise final state interactions., Comment: 7 pages, 8 figures
Published: 2013
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47. Search for the eta-mesic 4He with WASA-at-COSY detector

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bednarski, T., Bergmann, F. S., Berlowski, M., Bhatt, H., Buescher, M., Calen, H., Clement, H., Coderre, D., Czerwinski, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Foehl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullstroem, C. -O., Hauenstein, F., Heijkenskjoeld, L., Hejny, V., Hinterberger, F., Hodana, M., Hoeistad, B., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Klos, B., Krapp, M., Krzemien, W., Kulessa, P., Kupsc, A., Lalwani, K., Lersch, D., Li, L., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Nandi, B. K., Niedzwiecki, S., Ohm, H., Ozerianska, I., del Rio, E. Perez, Plucinski, P., Podkopal, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Schmidt, A., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Stroeher, H., Szczurek, A., Tolba, T., Trzcinski, A., Varma, R., Vlasov, P., Wagner, G. J., Weglorz, W., Wolke, M., Wronska, A., Wuestner, P., Wurm, P., Yamamoto, A., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zielinski, M. J., Zipper, W., Zlomanczuk, J., Zupranski, P., and Zurek, M.
Subjects: Nuclear Experiment
Abstract: An exclusive measurement of the excitation function for the dd->3Heppi- reaction was performed at the Cooler Synchrotron COSY-Juelich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematic threshold for the eta meson production in the dd->4He-eta reaction at 2.336 GeV/c. The corresponding excess energy with respect to the 4He-eta system varied from -51.4MeV to 22MeV. The integrated luminosity in the experiment was determined using the dd->3Hen reaction. The shape of the excitation function for the dd->3Heppi- was examined. No signal of the 4He-eta bound state was observed. An upper limit for the cross-section for the bound state formation and decay in the process dd->(4He-eta)bound->3Heppi- was determined on the 90% confidence level and it varies from 20nb to 27nb for the bound state width ranging from 5MeV to 35MeV, respectively., Comment: 8 pages, 9 figures
Published: 2013
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48. Isospin Decomposition of the Basic Double-Pionic Fusion in the Region of the ABC Effect

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bednarski, T., Bergmann, F. S., Berlowski, M., Bhatt, H., Büscher, M., Calen, H., Clement, H., Coderre, D., Czerwinski, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Goswami, A., Grigoryev, K., Gullstrom, C. -O., Hauenstein, F., Heijkenskjol, L., Hejny, V., Hinterberger, F., Hodana, M., Hoistad, B., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Klos, B., Krapp, M., Krzemien, W., Kulessa, P., Kupsc, A., Lalwani, K., Lersch, D., Li, L., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Nandi, B. K., Niedzwiecki, S., Ohm, H., Ozerianska, I., del Rio, E. Perez, Plucinski, P., Podkopal, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Schmidt, A., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Stephan, E., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Tolba, T., Trzcinski, A., Varma, R., Vlasov, P., Wagner, G. J., Wkeglorz, W., Wolke, M., Wronska, A., Wüstner, P., Wurm, P., Yamamoto, A., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zielinski, M. J., Zipper, W., Zlomanczuk, J., Zupranski, P., and Zurek, M.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Exclusive and kinematically complete high-statistics measurements of the basic double pionic fusion reactions pn -> dpi0pi0, pn -> d pi+pi- and pp -> dpi+pi0 have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the dpi0pi0 channel exhibits the ABC effect, i.e. a low-mass enhancement in the pipi-invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the dpi+pi0 channel shows a smooth behavior consistent with the conventional t-channel Delta Delta process. The dpi+pi- data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account.
Published: 2012
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49. ABC Resonance Structure in the Double-Pionic Fusion to 4He

Author: Adlarson, P., Augustyniak, W., Bardan, W., Bashkanov, M., Bednarski, T., Bergmann, F. S., Berlowski, M., Bhatt, H., Brinkmann, K. T., Buescher, M., Calen, H., Clement, H., Coderre, D., Czerwinski, E., Demmich, K., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Foehl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Grigoryev, K., Gullstroem, C. O., Hauenstein, F., Heijkenskjold, L., Hejny, V., Hinterberger, F., Hodana, M., Hoistad, B., Husmann, C., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khan, F. A., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Klos, B., Krzemien, W., Kulessa, P., Kupsc, A., Lalwani, K., Lersch, D., Li, L., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Mikirtychiants, M., Morsch, H. P., Moskal, P., Nandi, B. K., Niedzwiecki, S., Ohm, H., Ozerianska, I., Pauly, C., del Rio, E. Perez, Petukhov, Y., Plucinski, P., Podkopal, P., Prasuhn, D., Pricking, A., Pszczel, D., Pysz, K., Pyszniak, A., Redmer, C. F., Ritman, J., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Schmidt, A., Serdyuk, V., Shah, N., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Sterzenbach, G., Stockhorst, H., Stroeher, H., Szczurek, A., Tolba, T., Trzcinski, A., Varma, R., Vlasov, P., Wagner, G. J., Wkeglorz, W., Wolke, M., Wronska, A., Wuestner, P., Wurm, P., Yamamoto, A., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zielinski, M. J., Zipper, W., Zlomanczuk, J., and Zupranski, P.
Subjects: Nuclear Experiment, High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: Exclusive and kinematically complete high-statistics measurements of the double pionic fusion reaction $dd \to ^4$He$\pi^0\pi^0$ have been performed in the energy range 0.8 - 1.4 GeV covering thus the region of the ABC effect, which denotes a pronounced low-mass enhancement in the $\pi\pi$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observation in the basic $pn \to d \pi^0\pi^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. The maximum occurs at m=2.37 GeV + 2$m_N$, i.e. at the same position as in the basic reaction. The observed resonance width $\Gamma \approx$ 160 MeV can be understood from broadening due to Fermi motion of the nucleons in initial and final nuclei together with collision damping. Differential cross sections are described equally well by the hypothesis of a $pn$ resonance formation during the reaction process.
Published: 2012
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50. The production of K+K- pairs in proton-proton collisions at 2.83 GeV

Author: Ye, Q. J., Hartmann, M., Maeda, Y., Barsov, S., Buescher, M., Chiladze, D., Dymov, S., Dzyuba, A., Gao, H., Gebel, R., Hejny, V., Kacharava, A., Keshelashvili, I., Kiselev, Yu. T., Khoukaz, A., Koptev, V. P., Kulessa, P., Kulikov, A., Lorentz, B., Mersmann, T., Merzliakov, S., Mikirtytchiants, S., Nekipelov, M., Ohm, H., Paryev, E. Ya., Polyanskiy, A., Serdyuk, V., Stein, H. J., Stroeher, H., Trusov, S., Valdau, Yu., Wilkin, C., and Wuestner, P.
Subjects: Nuclear Experiment, Nuclear Theory
Abstract: Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data., Comment: 12 pages, 12 figures, 3 tables
Published: 2012
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