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1,070 results on '"JARCZYK, L"'

1. 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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2. 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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3. 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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4. 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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5. 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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6. 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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7. 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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8. 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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9. 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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10. 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

11. 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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12. 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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13. 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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14. 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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15. 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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16. 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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17. 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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18. 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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19. 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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20. 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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21. 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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22. 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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23. 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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24. 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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25. 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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26. 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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27. 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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28. 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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29. Sequential and simultaneous emission of fragments from p+Al collisions

Author: Fidelus, M., Filges, D., Goldenbaum, F., Hodde, H., Jany, A., Jarczyk, L., Kamys, B., Kistryn, M., Kistryn, St., Kliczewski, St., Kozik, E., Kulessa, P., Machner, H., Magiera, A., Piskor-Ignatowicz, B., Pysz, K., Rudy, Z., Sharma, Sushil K., Siudak, R., and Wojciechowski, M.
Subjects: Nuclear Experiment
Abstract: The energy and angular dependencies of double differential cross sections d^2sigma/dOmegadE were measured for p,d,t,^{3,4,6}He,^{6,7,8}Li,{7,9,10}Be, and ^{10,11,12}B produced in collisions of 1.2, 1.9, and 2.5 GeV protons with an Al target. The spectra and angular distributions of Li, Be, and B isotopes indicate a presence of two contributions: an isotropic, low energy one which is attributed to the evaporation of particles from excited remnants of the intranuclear cascade, and an anisotropic part which is interpreted to be due to multifragmentation of the remnants. It was found that such a hypothesis leads to very good description of spectra and angular distributions of all intermediate mass fragments (^6He-^{12}B) using the critical value of the excitation energy per nucleon as a single parameter, varying slowly with the beam energy., Comment: 7 figures
Published: 2011

30. Exclusive Measurement of the eta --> pi+ pi- gamma Decay

Author: Adlarson, P., Adolph, C., Augustyniak, W., Bardan, W., Bashkanov, M., Bednarski, T., Bergmann, F. S., Berłowski, M., Bhatt, H., Brinkmann, K. -T., Büscher, M., Calén, H., Clement, H., Coderre, D., Czerwiński, E., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Grigoryev, K., Gullström, C. -O., Hanhart, C., Heijkenskjöld, L., Heimlich, J., Hejny, V., Hinterberger, F., Hodana, M., Höistad, B., Jacewicz, M., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khakimova, O., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Kłos, B., Kren, F., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Leupold, S., Lorentz, B., Magiera, A., Maier, R., Mariański, B., Marciniewski, P., Meißner, U. -G., Mikirtychiants, M., Morsch, H. -P., Moskal, P., Nandi, B. K., Niedźwiecki, S., Ohm, H., Passfeld, A., Pauly, C., del Rio, E. Perez, Petri, T., Petukhov, Y., Piskunov, N., Pluciński, P., Podkopał, P., Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., Pyszniak, A., Rausmann, T., 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., Sterzenbach, G., Stockhorst, H., Stollenwerk, F., Szczurek, A., Täschner, A., Terschlüsen, C., Tolba, T., Trzciński, A., Varma, R., Vlasov, P., Wagner, G. J., Węglorz, W., Winnemöller, A., Wirzba, A., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, M. J., Zipper, W., Złomańczuk, J., and Żuprański, P.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: An exclusive measurement of the decay eta --> pi+ pi- gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd --> 3He X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13340\pm140 events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta --> pi+ pi- gamma. A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi+ pi- system., Comment: 7 pages, 10 figures, submitted to Phys.Lett.B
Published: 2011
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31. \pi^0 \pi^0 Production in Proton-Proton Collisions at Tp=1.4 GeV

Author: Adlarson, P., Adolph, C., Augustyniak, W., Bashkanov, M., Bednarski, T., Bergmann, F. S., Berłowski, M., Bhatt, H., Brinkmann, K. --T., Büscher, M., Calén, H., Clement, H., Coderre, D., Czerwiński, E., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Grigoryevj, K., Gullström, C. --O., Heijkenskjöld, L., Heimlich, J., Hejny, V., Hinterberger, F., Hodana, M., Höistad, B., Jacewicz, M., Janusz, M., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Khakimova, O., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Kłos, B., Kren, F., Krzemień, W., Kulessa, P., Kupść, A., Lalwani, K., Lorentz, B., Machner, H., Magiera, A., Maier, R., Mariański, B., Marciniewski, P., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Nandi, B. K., Niedźwiecki, S., Ohm, H., Passfeld, A., Pauly, C., del Rio, E. Perez, Petukhov, Y., Piskunov, N., Pluciński, P., Podkopał, P., Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., Rausmann, T., Redmer, C. F., Ritman, J., Rudy, Z., Sawant, S., Schadmand, S., Schmidt, A., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Sterzenbach, G., Stockhorst, H., Szczurek, A., Täschner, A., Tolba, T., Trzciński, A., Varma, R., Vlasov, P., Wagner, G. J., Weglorz, W., Wiedner, U., Winnemöller, A., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, M. J., Zipper, W., Złomańczuk, J., and Zuprański, P.
Subjects: High Energy Physics - Experiment
Abstract: The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +- 21_systematic +- 58_normalization) mub. In order to to study the production mechanism, differential kinematical distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found, Comment: Submitted to PLB
Published: 2011
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32. ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?

Author: Adlarson, P., Adolph, C., Augustyniak, W., Baru, V., Bashkanov, M., Bergmann, F. S., Berlowski, M., Bhatt, H., Brinkmann, K. -T., Buescher, M., Calen, H., Clement, H., Coderre, D., Czerwinski, E., Doroshkevich, E., Ekstrom, C., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Foehl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Grigoryev, K., Grishina, V., Gullstrom, C. -O., Hampe, J., Hanhart, C., Heijkenskj, L., Hejny, V., Hinterberger, F., Hodana, M., Hoistad, B., Jacewicz, M., Janusz, M., Jany, A., Jany, B. R., Jarczyk, L., Jaus, J., Johansson, T., Kamys, B., Kemmerling, G., Khakimova, O., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Klos, B., Kren, F., Krzemien, W., Kulessa, P., Kullander, S., Kupsc, A., Lalwani, K., Lorentz, B., Magiera, A., Maier, R., Marciniewski, P., Marianski, B., Mikirtychiants, M., Moskal, P., Morsch, H. -P., Nandi, B. K., Ohm, H., Passfeld, A., Pauly, C., del Rio, E. Perez, Petukhov, Y., Piskunov, N., Plucinski, P., Podkopal, P., Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., Rausmann, T., Redmer, C. F., Ritman, J., Roy, A., Ruber, R. J. M. Y., Rudy, Z., Schadmand, S., Schmidt, A., Schroeder, W., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Sterzenbach, G., Stockhorst, H., Stroeher, H., Szczurek, A., Taeschner, A., Tolba, T., Trzcinski, A., Varma, R., Vlasov, P., Wagner, G. J., Weglorz, W., Winnemoeller, A., Wirzba, A., Wolke, M., Wronska, A., Wuestner, P., Wurm, P., Yurev, L., Zabierowski, J., Zielinski, M. J., Zipper, W., Zlomanczuk, J., and Zupranski, P.
Subjects: Nuclear Experiment
Abstract: We report on a high-statistics measurement of the basic double pionic fusion reaction $pn \to d\pi^0\pi^0$ over the energy region of the so-called ABC effect, a pronounced low-mass enhancement in the $\pi\pi$-invariant mass spectrum. The measurements were performed with the WASA detector setup at COSY. The data reveal the ABC effect to be associated with a Lorentzian shaped energy dependence in the integral cross section. The observables are consistent with a resonance with $I(J^P) =0(3^+)$ in both $pn$ and $\Delta\Delta$ systems. Necessary further tests of the resonance interpretation are discussed.
Published: 2011
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33. Measurement of the invariant mass distributions for the pp -> ppeta' reaction at excess energy of Q = 16.4 MeV

Author: Klaja, P., Moskal, P., Czerwinski, E., Czyzykiewicz, R., Deloff, A., Gil, D., Grzonka, D., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, J., Nakayama, K., Oelert, W., Ritman, J., Sefzick, T., Siemaszko, M., Silarski, M., Smyrski, J., Taeschner, A., Wolke, M., Zdebik, J., Zielinski, M., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: The proton-proton and proton-eta' invariant mass distributions have been determined for the pp -> ppeta' reaction at an excess energy of Q = 16.4 MeV. The measurement was carried out using the COSY-11 detector setup and the proton beam of the cooler synchrotron COSY. The shapes of the determined invariant mass distributions are similar to those of the pp -> ppeta reaction and reveal an enhancement for large relative proton-proton momenta. This result, together with the fact that the proton-eta interaction is much stronger that the proton-eta' interaction, excludes the hypothesis that the observed enhancement is caused by the interaction between the proton and the meson.
Published: 2010
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34. Invariant mass distributions for the pp to p p eta reaction at Q=10 MeV

Author: Moskal, P., Czyzykiewicz, R., Czerwinski, E., Gil, D., Grzonka, D., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, J., Klaja, P., Krzemien, W., Oelert, W., Ritman, J., Sefzick, T., Siemaszko, M., Silarski, M., Smyrski, J., Taschner, A., Wolke, M., Wustner, P., Zdebik, J., Zielinski, M. J., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: Proton-proton and proton-eta invariant mass distributions and the total cross section for the pp to pp eta reaction have been determined near the threshold at an excess energy of Q=10 MeV. The experiment has been conducted using the COSY-11 detector setup and the cooler synchrotron COSY. The determined invariant mass spectra reveal significant enhancements in the region of low proton-proton relative momenta, similarly as observed previously at higher excess energies of Q=15.5 MeV and Q= 40MeV., Comment: 6 pages, 3 figures, submitted to Eur.Phys. J. A
Published: 2009
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35. Evidence of Ni break-up from total production cross sections in p+Ni collisions

Author: Budzanowski, A., Fidelus, M., Filges, D., Goldenbaum, F., Hodde, H., Jarczyk, L., Kamys, B., Kistryn, M., Kistryn, St., Kliczewski, St., Kowalczyk, A., Kozik, E., Kulessa, P., Machner, H., Magiera, A., Piskor-Ignatowicz, B., Pysz, K., Rudy, Z., Siudak, R., and Wojciechowski, M.
Subjects: Nuclear Experiment
Abstract: The total production cross sections of light charged particles (LCPs), intermediate mass fragments (IMFs) and heavy reaction products of p+Ni collisions available in the literature have been compared with predictions of a two-step model in the proton beam energy range from reaction threshold up to approximately 3 GeV. Model cross sections were calculated assuming, that the reaction proceeds via an intranuclear cascade of nucleon-nucleon collisions followed by evaporation of particles from an equilibrated, heavy target residuum. The shape of the excitation functions was well described by model calculations for all reaction products. The magnitude of the cross sections was reasonably well reproduced for heavy reaction products, i.e. for nuclei heavier than Al, but the cross sections for lighter products were systematically underestimated. This fact was used as an argument in favor of a significant break-up contribution to the reaction mechanism. The present conclusions are supported by recently published results of investigations of differential cross sections in p+Ni collisions, which showed that hypothesis of the break-up of target nucleus is indispensable for a good reproduction of d2 sigma/dOmega dE for LCPs and IMFs., Comment: 5 pages, 4 figures
Published: 2009

36. Generalized Dalitz Plot analysis of the near threshold pp-->ppK+K- reaction in view of the K+K- final state interaction

Author: Silarski, M., Moskal, P., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, J., Klaja, P., Krzemien, W., Oelert, W., Ritman, J., Sefzick, T., Siemaszko, M., Smyrski, J., Taschner, A., Winter, P., Wolke, M., Wustner, P., Zielinski, M., Zipper, W., and Zdebik, J.
Subjects: High Energy Physics - Phenomenology
Abstract: The excitation function for the $pp\to ppK^+K^-$ reaction revealed a significant enhancement close to threshold which may plausibly be assigned to the influence of the $pK^-$ and $K^+K^-$ final state interactions. In an improved reanalysis of COSY-11 data for the $pp\to ppK^+K^-$ reaction at excess energies of Q = 10 MeV and 28 MeV including the proton-K- interaction the enhancement is confirmed. Invariant mass distributions for the two- and three-particle subsystems allow to test at low excess energies the ansatz and parameters for the description of the interaction in the ppK+K- system as derived from the COSY-ANKE data. Finally, based for the first time on the low energy K+K- invariant mass distributions and the generalized Dalitz plot analysis, we estimate the scattering length for the K+K- interaction to be |Re(a_K^+K^-)| = 0.5 + 4.0 -0.5 fm and Im(a_K^+K^-) = 3.0 +- 3.0 fm., Comment: 8 pages, 7 figures, to be published in Phys. Rev. C
Published: 2009
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37. Variation of nonequilibrium processes in p+Ni system with beam energy

Author: Budzanowski, A., Fidelus, M., Filges, D., Goldenbaum, F., Hodde, H., Jarczyk, L., Kamys, B., Kistryn, M., Kistryn, St., Kliczewski, St., Kowalczyk, A., Kozik, E., Kulessa, P., Machner, H., Magiera, A., Piskor-Ignatowicz, B., Pysz, K., Rudy, Z., Siudak, R., and Wojciechowski, M.
Subjects: Nuclear Experiment
Abstract: The energy and angular dependence of double differential cross sections dsigma/dOmega dE were measured for p, d, t, 3,4He, 6,7Li, 7,9Be, and 10,11B produced in collisions of 0.175 GeV protons with Ni target. The analysis of measured dfferential cross sections allowed to extract total production cross sections for ejectiles listed above. The shape of the spectra and angular distributions indicate the presence of other nonequilibrium processes besides the emission of nucleons from the intranuclear cascade, and besides the evaporation of various particles from remnants of intranuclear cascade. These nonequilibrium processes consist of coalescence of nucleons into light charged particles during the intranuclear cascade, of the fireball emission which contributes to the cross sections of protons and deuterons, and of the break-up of the target nucleus which leads to the emission of intermediate mass fragments. All such processes were found earlier at beam energies 1.2, 1.9, and 2.5 GeV for Ni as well as for Au targets, however, significant differences in properties of these processes at high and low beam energy are observed in the present study., Comment: 10 pages, 9 figures
Published: 2009
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38. Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

Author: Budzanowski, A., Fidelus, M., Filges, D., Goldenbaum, F., Hodde, H., Jarczyk, L., Kamys, B., Kistryn, M., Kistryn, St., Kliczewski, St., Kowalczyk, A., Kozik, E., Kulessa, P., Machner, H., Magiera, A., Piskor-Ignatowicz, B., Pysz, K., Rudy, Z., Siudak, R., and Wojciechowski, M.
Subjects: Nuclear Experiment
Abstract: The energy and angular dependence of double differential cross sections d2sigma/dOmega dE were measured for p, d, t, 3,4,6He, 6,7,8Li, 7,9,10Be, 10,11B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions does almost not change whereas the absolute value of the cross sections increases by a factor about 1.7 for all ejectiles in this beam energy range. It was found that energy and angular dependencies of the cross sections cannot be reproduced by the microscopic model of intranuclear cascade with coalescence of nucleons and the statistical model for evaporation of particles from excited, equilibrated residual nuclei. The inclusion of nonequilibrium processes, described by a phenomenological model of the emission from fast and hot moving sources, resulting from break-up of the target nucleus by impinging proton, leads to very good reproduction of data. Cross sections of these processes are quite large, exhausting approximately half of the total production cross sections. Due to good reproduction of energy and angular dependencies of d2sigma/dOmega dE by model calculation it was possible to determine total production cross sections for all studied ejectiles. Results obtained in this work point to the analogous reaction mechanism for proton induced reactions on Ni target as that observed previously for Au target in the same beam energy range., Comment: 11 pages, 10 figures
Published: 2009
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39. Search for the 3He-eta bound state at COSY-11

Author: Krzemien, W., Smyrski, J., Budzanowski, A., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, P., Moskal, P., Oelert, W., Przerwa, J., Ritman, J., Sefzick, T., Siemaszko, M., Silarski, M., Taeschner, A., Wolke, M., Wuestner, P., Zdebik, J., Zielinski, M. J., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: We have measured excitation function for dp -> ppp_pi- reaction near the eta production threshold. We observe an enhancement of the counting rate above the threshold which can originate from the production of the eta meson in the reaction dp -> 3He eta and its subsequent absorption on neutron in the 3He nucleus leading to creation of the p_pi- pair., Comment: Presented at 10th International Workshop on Meson Production, Properties and Interaction (MESON 2008), Cracow, Poland, 6 - 10 June 2008, 4 pages, 4 figures,references added
Published: 2008
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40. Isospin dependence of the eta prime meson production in nucleon-nucleon collisions

Author: Przerwa, J., Moskal, P., Budzanowski, A., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Jarczyk, L., Johansson, T., Kamys, B., Khoukaz, A., Klaja, P., Krzemien, W., Oelert, W., Piskor-Ignatowicz, C., Ritman, J., Rejdych, B., Sefzick, T., Siemaszko, M., Silarski, M., Smyrski, J., Taeschner, A., Wolke, M., Wuestner, P., Zdebik, J., Zielinski, M. J., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: A comparison of the close-to-threshold total cross section for the eta prime production in pp --> pp eta prime and pn --> pn eta prime reactions constitutes a tool to investigate the eta prime meson structure and the reaction mechanism in the channels of isospin I=0 and I=1 and may provide insight into the flavour-singlet (perhaps also into gluonium) content of the eta prime meson. In this contribution we present preliminary results of measurement of the quasi-free production of the eta prime meson in the proton-neutron collisions conducted using the COSY-11 facility., Comment: Presented at 10th International Workshop on Meson Production, Properties and Interaction (MESON 2008), Cracow, Poland, 6 - 10 June 2008
Published: 2008
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41. Study of the hadronic production of kaon pairs below the threshold for the phi meson

Author: Moskal, P., Silarski, M., Budzanowski, A., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, P., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Rejdych, B., Ritman, J., Sefzick, T., Siemaszko, M., Smyrski, J., Taschner, A., Winter, P., Wolke, M., Wustner, P., Zielinski, M. J., Zipper, W., and Zdebik, J.
Subjects: Nuclear Experiment
Abstract: The near threshold production of K+K- pairs in proton-proton collisions has been investigated at the cooler synchrotron COSY below and above the threshold for the $\phi$ meson using the COSY-11 and ANKE facilities, respectively. The excitation function determined for the pp-->ppK+K- reaction revealed a statistically significant enhancement close to the threshold which may plausibly be assigned to the influence of the K-p interaction. In addition, observed consistently by both groups, a strong enhancement at low values of the ratio of the K-p to K+p invariant mass distributions shows that the proton interacts much stronger with K- than with K+. In this report we focus on the measurements performed by the COSY-11 collaboration. We explain the experimental method used and present main results of completed analyses as well as a new qualitative elaboration of the ppK+K- events population on the Goldhaber plot. We conclude with the observation that event densities increase at the region where the influence from the K+K- interaction is expected., Comment: 5 pages, 5 figures, Talk given at International Workshop on e+ e- Collisions from Phi to Psi (PHIPSI08), Frascati, Italy, 7-10 Apr 2008
Published: 2008
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42. Near threshold production of the eta meson via the quasi-free pn --> pn eta reaction

Author: Moskal, P., Czyzykiewicz, R., Adam, H. -H., Bass, S. D., Budzanowski, A., Czerwinski, E., Gil, D., Grzonka, D., Janusz, M., Jarczyk, L., Johansson, T., Kamys, B., Khoukaz, A., Kilian, K., Klaja, P., Majewski, J., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Rejdych, B., Ritman, J., Rozek, T., Sefzick, T., Siemaszko, M., Silarski, M., Smyrski, J., Taeschner, A., Wolke, M., Wuestner, P., Zielinski, M. J., Zipper, W., and Zdebik, J.
Subjects: High Energy Physics - Experiment
Abstract: Total cross sections for the quasi-free pn --> pn eta reaction in the range from the kinematical threshold up to 20 MeV excess energy have been determined. At threshold they exceed corresponding cross sections for the pp --> pp eta reaction by a factor of about three in contrast to the factor of six established for higher excess energies. To large extent, the observed decrease of the ratio sigma(pn --> pn eta)/sigma(pp --> pp eta) towards threshold may be assigned to the different energy dependence of the proton-proton and proton-neutron final state interactions. The experiment has been conducted using a proton beam of the cooler synchrotron COSY and a cluster jet deuteron target. The proton-neutron reactions were tagged by the spectator proton whose momentum was measured for each event. Protons and neutron outgoing from the pn --> pn eta reaction have been registered by means of the COSY-11 facility, an apparatus dedicated for threshold meson production., Comment: 15 pages, 6 figures, submitted to Phys. Rev. C
Published: 2008
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43. Competition of coalescence and 'fireball' processes in nonequilibrium emission of light charged particles from p+Au collisions

Author: Budzanowski, A., Fidelus, M., Filges, D., Goldenbaum, F., Hodde, H., Jarczyk, L., Kamys, B., Kistryn, M., Kistryn, St., Kliczewski, St., Kowalczyk, A., Kozik, E., Kulessa, P., Machner, H., Magiera, A., Piskor-Ignatowicz, B., Pysz, K., Rudy, Z., Siudak, R., and Wojciechowski, M.
Subjects: Nuclear Experiment
Abstract: The energy and angular dependence of double differential cross sections was measured for p,d,t,He,Li,Be, and B isotopes produced in collisions of 1.2 and 1.9 GeV protons with Au target. The shape of the spectra and angular distributions almost does not change in the beam energy range from 1.2 to 2.5 GeV, however, the absolute value of the cross sections increases for all ejectiles. A phenomenological model of two emitting, moving sources reproduces very well spectra and angular distributions of intermediate mass fragments. Double differential cross sections for light charged particles (LCP) were analyzed in the frame of the microscopic model of intranuclear cascade (INC) with coalescence of nucleons and statistical model for evaporation of particles from excited residual nuclei. Energy and angular dependencies of data agree satisfactorily neither with predictions of microscopic intranuclear cascade calculations for protons, nor with coalescence calculations for other LCP. Phenomenological inclusion of another reaction mechanism - emission of LCP from a "fireball", i.e., fast and hot moving source - combined with the microscopic model calculations of INC, coalescence and evaporation of particles leads to very good description of the data. It was found that nonequilibrium processes are very important for production of LCP. They exhaust 40-80% of the total cross sections - depending on the emitted particles. Coalescence and "fireball" emission give comparable contributions to the cross sections with exception of 3He data where coalescence clearly dominates. The ratio of sum of all nonequilibrium processes to those proceeding through stage of statistical equilibrium does almost not change in the beam energy range from 1.2 GeV to 2.5 GeV for all light charged particles., Comment: 14 pages, 12 figures, IV tables, \pacs{25.40.-h,25.40.Sc,25.40.Ve}
Published: 2008
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44. Dynamics of the near threshold eta meson production in proton-proton interaction

Author: Czyzykiewicz, R., Moskal, P., Adam, H. -H., Budzanowski, A., Czerwinski, E., Gil, D., Grzonka, D., Hodana, M., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Kilian, K., Klaja, P., Lorentz, B., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Rejdych, B., Ritman, J., Sefzick, T., Siemaszko, M., Silarski, M., Smyrski, J., Taschner, A., Ulbrich, K., Winter, P., Wolke, M., Wustner, P., Zielinski, M. J., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: We present the results of measurements of the analysing power for the p(pol)p --> pp eta reaction at the excess energies of Q=10 and 36 MeV, and interpret these results within the framework of the meson exchange models. The determined values of the analysing power at both excess energies are consistent with zero implying that the eta meson is produced predominantly in s-wave., Comment: 3 pages, 3 figures, Presented at the Workshop on the physics of excited nucleons (NSTAR 2007), 5-8 September 2007, Bonn, Germany
Published: 2007
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45. Near threshold production of the pseudoscalar mesons at the COSY-11 facility

Author: Moskal, P., Czyzykiewicz, R., Adam, H. -H., Budzanowski, A., Czerwinski, E., Gil, D., Grzonka, D., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Kilian, K., Klaja, P., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Rejdych, B., Ritman, J., Sefzick, T., Siemaszko, M., Silarski, M., Smyrski, J., Taschner, A., Wolke, M., Winter, P., Wustner, P., Zielinski, M. J., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: We summarise measurements of the COSY-11 collaboration concerning the excitation functions of the near threshold pseudoscalar meson production in the proton-proton interaction. The results are discussed in the context of the meson-nucleon and hyperon-nucleon interactions. We conclude that the $\eta$-proton interaction is significantly stronger than the eta'-proton interaction. Similarly, we found that the hyperon Lambda interacts with the nucleon considerably stronger than the hyperon Sigma, and that the interaction of (K-)-proton is much stronger than this of the (K+)-proton., Comment: 3 pages, 3 figures, Presented at the Workshop on the physics of excited nucleons (NSTAR 2007), 5-8 September 2007, Bonn, Germany
Published: 2007
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46. Non-equilibrium emission of complex fragments from p+Au collisions at 2.5 GeV proton beam energy

Author: Budzanowski, A., Filges, D., Goldenbaum, F., Heczko, A., Hodde, H., Jarczyk, L., Kamys, B., Kistryn, M., Kistryn, St., Kliczewski, St., Kowalczyk, A., Smoluchowski, M., Kozik, E., Kulessa, P., Machner, H., Magiera, A., Migdal, W., Paul, N., Piskor-Ignatowicz, B., Puchala, M., Pysz, K., Rudy, Z., Siudak, R., and Wojciechowski, M.
Subjects: Nuclear Experiment
Abstract: Energy and angular dependence of double differential cross sections d$^2\sigma$/d$\Omega$dE was measured for reactions induced by 2.5 GeV protons on Au target with isotopic identification of light products (H, He, Li, Be, and B) and with elemental identification of heavier intermediate mass fragments (C, N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction mechanisms give comparable contributions to the cross sections. The intranuclear cascade of nucleon-nucleon collisions followed by evaporation from an equilibrated residuum describes low energy part of the energy distributions whereas another reaction mechanism is responsible for high energy part of the spectra of composite particles. Phenomenological model description of the differential cross sections by isotropic emission from two moving sources led to a very good description of all measured data. Values of the extracted parameters of the emitting sources are compatible with the hypothesis claiming that the high energy particles emerge from pre-equilibrium processes consisting in a breakup of the target into three groups of nucleons; small, fast and hot fireball of $\sim$ 8 nucleons, and two larger, excited prefragments, which emits the light charged particles and intermediate mass fragments. The smaller of them contains $\sim$ 20 nucleons and moves with velocity larger than the CM velocity of the proton projectile and the target. The heavier prefragment behaves similarly as the heavy residuum of the intranuclear cascade of nucleon-nucleon collisions. %The mass and charge dependence of the total production cross %sections was extracted from the above analysis for all observed %reaction products. This dependence follows the power low behavior %(A$^{-\tau}$ or Z$^{-\tau}$).
Published: 2007
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47. Measurement of the dp -->3He eta reaction near threshold

Author: Smyrski, J., Adam, H. -H., Budzanowski, A., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, P., Mersmann, T., Moskal, P., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Rejdych, B., Ritman, J., Rozek, T., Sefzick, T., Siemaszko, M., Taeschner, A., Winter, P., Wolke, M., Wuestner, P., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: Total and differential cross sections for the dp --> 3He eta reaction have been measured near threshold for 3He center-of-mass momenta in the range from 17.1 MeV/c to 87.5 MeV/c. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target detecting the 3He ejectiles with the COSY-11 facility. The forward-backward asymmetries of the differential cross sections deviate clearly from zero for center-of-mass momenta above 50 MeV/c indicating the presence of higher partial waves in the final state. Below 50 MeV/c center-of-mass momenta a fit of the final state enhancement factor to the data of the total cross sections results in the 3He eta scattering length of a = |2.9 +/- 0.6| + i (3.2 +/- 0.4) fm.
Published: 2007
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48. Study of the 3He-eta system in d-p collisions

Author: Smyrski, J., Adam, H. -H., Budzanowski, A., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, P., Moskal, P., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Ritman, J., Rozek, T., Sefzick, T., Siemaszko, M., Taeschner, A., Winter, P., Wolke, M., Wuestner, P., and Zipper, W.
Subjects: Nuclear Experiment
Abstract: We have measured excitation functions for the d+p->3He+X, (X=pi0, eta) channels near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The excitation function for the reaction d+p->3He+pi0 does not show any structure which could originate from the decay of 3He-eta bound state. We measured also the threshold excitation curve for the d+p->3He+X process, however, contrary to the SATURNE results, we observe no cusp near the eta threshold., Comment: Talk given at 18th International IUPAP Conference on Few-Body Problems in Physics, 21-26 August, 2006, Santos, Brazil, 4 pages, 6 figures, will be published in Nuclear Physics A
Published: 2006
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49. Near threshold eta meson production in dp collisions

Author: Piskor-Ignatowicz, C., Smyrski, J., Moskal, P., Adam, H. -H., Budzanowski, A., Czerwinski, E., Czyzykiewicz, R., Gil, D., Grzonka, D., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Klaja, P., Majewski, J., Oelert, W., Przerwa, J., Ritman, J., Rozek, T., Sefzick, T., Siemaszko, M., Taeschner, A., Winter, P., Wolke, M., Wuestner, P., and Zipper, W.
Subjects: High Energy Physics - Experiment
Abstract: Preliminary results of recent measurements of the near threshold eta meson production in the dp-->dp eta reaction are presented. The experiment was performed at the COSY-Juelich accelerator with the use of the COSY-11 detection system. Data were taken for three values of deuteron beam momenta corresponding to excess energies of 3.2, 6.1 and 9.2 MeV. The energy dependence of the total cross section confirms a strong effect of the final state interaction., Comment: Talk given at 9th International Workshop on Meson Production, Properties and Interaction, Cracow, Poland, 9-13 June 2006. 5 pages, 3 figures
Published: 2006
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50. Mechanism of the close-to-threshold production of the eta meson

Author: Czyzykiewicz, R., Moskal, P., Adam, H. -H., Budzanowski, A., Czerwinski, E., Gil, D., Grzonka, D., Hodana, M., Janusz, M., Jarczyk, L., Kamys, B., Khoukaz, A., Kilian, K., Klaja, P., Lorentz, B., Oelert, W., Piskor-Ignatowicz, C., Przerwa, J., Rejdych, B., Ritman, J., Sefzick, T., Siemaszko, M., Smyrski, J., Taeschner, A., Ulbrich, K., Winter, P., Wolke, M., Wuestner, P., and Zipper, W.
Subjects: High Energy Physics - Experiment
Abstract: Measurements of the analysing power for the p(pol)p --> ppeta reaction have been performed in the close-to-threshold energy region at beam momenta of p_{beam}=2.010 and 2.085 GeV/c, corresponding to excess energies of Q=10 and 36 MeV, respectively. The determined analysing power is essentially consistent with zero implying that the eta meson is produced predominantly in the s-wave at both excess energies. The angular dependence of the analysing power, combined with the hitherto determined isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal a statistically significant indication that the excitation of the nucleon to the S_{11}(1535) resonance, the process which intermediates the production of the eta meson, is predominantly due to the exchange of the pi meson between the colliding nucleons., Comment: 4 pages, 4 figures, content added
Published: 2006
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