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31 results on '"Khakimova O"'

1. 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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2. 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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3. Exclusive Measurement of the $pp \to nn\pi^+\pi^+$ Reaction at 1.1 GeV

Author

Bashkanov, M., Bogoslawsky, D., Calen, H., Clement, H., Doroshkevich, E., Demiroers, L., Ekstrom, C., Fransson, K., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupsc, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Shwartz, B., Stepaniak, J., Thorngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., and Zlomanczuk, J.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

First exclusive data for the $pp \to nn\pi^+\pi^+$ reaction have been obtained at CELSIUS with the WASA detector setup at a beam energy of $T_p$ = 1.1 GeV. Total and differential cross sections disagree with theoretical calculations, which predict the $\Delta\Delta$ excitation to be the dominant process at this beam energy. Instead the data require the excitation of a higher-lying $\Delta$ state, most likely the $\Delta(1600)$, to be the leading process.

Published
2010

4. Delta Delta Excitation in Proton-Proton Induced pi0pi0 Production

Author

Skorodko, T., Bashkanov, M., Bogoslawsky, D., Calen, H., Clement, H., Doroshkevich, E., Demiroers, L., Ekstroem, C., Fransson, K., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupsc, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Schoenning, K., Scobel, W., Shwartz, B., Stepaniak, J., Thoerngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

Exclusive measurements of the $pp \to pp\pi^0\pi^0$ reaction have been performed at CELSIUS/WASA at energies from threshold up to $T_p$ = 1.3 GeV. Total and differential cross sections have been obtained. Here we concentrate on energies $T_p \ge$ 1 GeV, where the $\Delta\Delta$ excitation becomes the leading process. No evidence is found for a significant ABC effect beyond that given by the conventional $t$-channel $\Delta\Delta$ excitation. This holds also for the double-pionic fusion to the quasibound $^2$He. The data are compared to model predictions, which are based on both pion and $\rho$ exchange. Total and differential cross sections are at variance with these predictions and call for a profound modification of the $\rho$-exchange. A phenomenological modification allowing only a small $\rho$ exchange contribution leads to a quantitative description of the data.

Published
2010
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5. Systematic Study of Two-Pion Production in NN Collisions -- from Single-Baryon to Di-Baryon Excitations

Author

Skorodko, T., Bashkanov, M., Clement, H., Doroshkevich, E., Khakimova, O., Kren, F., Pricking, A., and Wagner, G. J.

Subjects
Nuclear Experiment
Abstract

The two-pion production in nucleon-nucleon collisions has been studied by exclusive and kinematically complete experiments from threshold up to $T_p$ = 1.36 GeV at CELSIUS-WASA. At near-threshold energies the total and differential distributions for the $\pi^+\pi^-$ and $\pi^0\pi^0$ channels are dominated by Roper excitation and its decay into $N\sigma$ and $\Delta\pi$ channels. At beam energies $T_p >$ 1.1 GeV the $\Delta\Delta$ excitation governs the two-pion production process. In the $\pi^+\pi^+$ channel evidence is found for the excitation of a higher-lying I=3/2 resonance, favorably the $\Delta(1600)$. The isovector fusion processes leading to the deuteron and to quasi-stable $^2$He, respectively, %with the production of an isovector pion-pair exhibit no or only a modest ABC-effect, {\it i.e.} low-mass enhancement in the $\pi\pi$-invariant mass spectrum, and can be described by conventional $t$-channel $\Delta\Delta$ excitation. On the other hand, the isoscalar fusion process to the deuteron %with the production of an isoscalar pion-pair exhibits a dramatic ABC-effect correlated with a narrow resonance-like energy dependence in the total cross section with a width of only 50 MeV and situated at a mass 90 MeV below the $\Delta\Delta$ mass., Comment: Proceedings HADRON09

Published
2010
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6. Production of eta and 3pi mesons in the pd->3HeX reaction at 1360 and 1450 MeV

Author

Schoenning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demiroers, L., Ekstroem, C., Fransson, K., Geren, L., Gustafsson, L., Hoeistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., tegner, P. -E., Engblom, P. Thoerngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The cross sections of the pd -> 3He eta, pd -> 3He pi0 pi0 pi0 and pd -> 3He pi+ pi- pi0 reactions have been measured at beam kinetic energies T_p= 1360 MeV and T_p= 1450 MeV using the CELSIUS/WASA detector setup. At both energies, the differential cross section dsigma/dOmega of the eta meson in the pd -> 3He eta reaction shows a strong forward-backward asymmetry in the CMS. The ratio between the pd -> 3He pi+ pi- pi0 and the pd -> 3He pi0 pi0 pi0 cross sections has been analysed in terms of isospin amplitudes. The reconstructed invariant mass distributions of the pi-pi, 3He-pi and 3He-2pi systems provide hints on the role of nucleon resonances in the 3pi production process., Comment: Shorter version accepted to EPJA 10 pages 14 figures

Published
2010
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7. The pd --> ^3He eta pi0 reaction at T_p = 1450 MeV

Author

Schoenning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demiroers, L., Ekstroem, C., Fransson, K., Geren, L., Gustafsson, L., Hoeistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. -E., Thoerngren-Engblom, P., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, Jozef

Subjects
Nuclear Experiment
Abstract

The cross section for the pd --> ^3He eta pi0 reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring and detecting one ^3He and four photons from the decays of the two photons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant masses of all three pairs of final state particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi^0 momentum in the ^3Hepi^0 system., Comment: 10 pages, 5 figures

Published
2009
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8. Exclusive Measurements of pp -> dpi+pi0: Double-Pionic Fusion without ABC Effect

Author

Kren, F., Bashkanov, M., Bogoslawsky, D., Calen, H., Clement, H., Demiroers, L., Ekstrom, C., Fransson, k., Greiff, J., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Kohansson, T., Khakimova, O., Keleta, S., Koch, I., Kullander, S., Kupsc, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petren, H., Petukhov, Y., Povtoreijko, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Skorodko, T., Shwartz, B., Stepaniak, J., Thorngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

Exclusive measurements of the reaction pp -> dpi+pi0 have been carried out at T_p = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector pi+pi0 channel exhibits no enhancement at low invariant pipi masses, i. e. no ABC effect. The differential distributions are in agreement with the conventional t-channel Delta-Delta excitation process, which also accounts for the observed energy dependence of the total cross section. This is an update of a previously published version -- see important note at the end of the article.

Published
2009
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9. Two-Pion Production in Proton-Proton Collisions -- Experimental Total Cross Sections and their Isospin Decomposition

Author

Skorodko, T., Bashkanov, M., Bogoslawsky, D., Calen, H., Clement, H., Doroshkevich, E., Demiroers, L., Ekstrom, C., Fransson, K., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupsc, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Shwartz, B., Stepaniak, J., Thorngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The two-pion production in pp-collisions has been investigated at CELSIUS in exclusive measurements from threshold up to $T_p$ = 1.36 GeV. Total and differential cross sections have been obtained for the channels $pn\pi^+\pi^0$, $pp\pi^+\pi^-$, $pp\pi^0\pi^0$ and also $nn\pi^+\pi^+$. For intermediate incident energies $T_p >$ 1 GeV, i.e. in the region which is beyond the Roper excitation but at the onset of $\Delta\Delta$ excitation, the total $pp\pi^0\pi^0$ cross section falls behind theoretical predictions by as much as an order of magnitude near 1.2 GeV, whereas the $nn\pi^+\pi^+$ cross section is a factor of five larger than predicted. An isospin decompostion of the total cross sections exhibits a s-channel-like energy dependence in the region of the Roper excitation as well as a significant contribution of an isospin 3/2 resonance other than the $\Delta(1232)$. As possible candidates the $\Delta(1600)$ and the $\Delta(1700)$ are discussed.

Published
2009
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10. Exclusive measurement of two-pion production in the dd --> 4Hepipi reaction

Author

Keleta, S., Bargholtz, Chr., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demirors, L., Ekstrom, C., Fransson, K., Geren, L., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Pricking, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. -E., Engblom, P. Thorngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The results from the first kinematically complete measurement of the dd --> 4Hepipi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pipi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV, with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pipi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN--> dpi sub-processes., Comment: 20 pages including 18 figures

Published
2009
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11. Production of the omega meson in the pd --> 3He omega reaction at 1450 MeV and 1360 MeV

Author

Schonning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demirors, L., Ekstrom, C., Fransson, K., Geren, L., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Khemchandani, K. P., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. -E., Engblom, P. Thorngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The production of $\omega$ mesons in the $pd \to{}^3$He$ \omega$ reaction has been studied at two energies near the kinematic threshold, $T_p=1450$ MeV and $T_p=1360$ MeV. The differential cross section was measured as a function of the $\omega$ cm angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections., Comment: 10 pages, 13 figures

Published
2009
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12. Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements

Author

Bashkanov, M., Bargholtz, C., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demiroers, L., Doroshkevich, E., Duniec, D., Ekstrom, C., Fransson, K., Geren, L., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupsc, A., Lindberg, K., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Pricking, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. -E., Thorngren-Engblom, P., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The ABC effect - a puzzling low-mass enhancement in the $\pi\pi$ invariant mass spectrum - is well-known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on first exclusive and kinematically complete measurements of the most basic double pionic fusion reaction $pn \to d \pi^0\pi^0$ at 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a $(\pi\pi)_{I=L=0}$ channel phenomenon associated with both a resonance-like energy dependence in the integral cross section and the formation of a $\Delta\Delta$ system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.

Published
2008
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13. Polarisation of the omega meson in the pd-->3He+omega reaction at 1360 and 1450 MeV

Author

Schonning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demirors, L., Ekstrom, C., Fransson, K., Geren, L., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Koch, I., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. -E., Engblom, P. Thorngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The tensor polarisation of omega mesons produced in the pd-->3He+omega reaction has been studied at two energies near threshold. The 3He nuclei were detected in coincidence with the pi0pi+pi- or pi0gamma decay products of the omega. In contrast to the case of phi meson production, the omega mesons are found to be unpolarised. This brings into question the applicability of the Okubo-Zweig-Iizuka rule when comparing the production of vector mesons in low energy hadronic reactions., Comment: 11 pages, 4 figures

Published
2008
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14. The WASA Detector Facility at CELSIUS

Author

Bargholtz, Chr., Bashkanov, M., Berłowski, M., Bondar, A., Bogoslawsky, D., Brodowski, W., Brudvik, J., Calén, H., Capellaro, F., Chilingarov, A., Clement, H., Comfort, J., Demirörs, L., Ekström, C., Fransson, K., Fridén, C. -J., Gerén, L., Gornov, M., Grebenev, V., Greiff, J., Gurov, Y., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, A., Johansson, T., Keleta, S., Khakimova, O., Khoukaz, A., Kilian, K., Kimura, N., Koch, I., Kolachev, G., Kren, F., Kullander, S., Kupść, A., Kuzmin, A., Kuznetsov, A., Lindberg, K., Marciniewski, P., Meier, R., Messner, O., Morosov, B., Nawrot, A., Nefkens, B. M. K., Norman, G., Oelert, W., Pauly, C., Pettersson, H., Pivovarov, A., Pätzold, J., Petukhov, Y., Povtorejko, A., Reistad, D., Ruber, R. J. M. Y., Sandukovsky, S., Schönning, K., Scobel, W., Sefzick, T., Shafigullin, R., Shwartz, B., Sidorov, V., Skorodko, T., Sopov, V., Starostin, A., Stepaniak, J., Sukhanov, A., Tchernyshev, V., Tegnér, P. -E., Engblom, P. Thörngren, Tikhomirov, V., Toki, H., Turowiecki, A., Wagner, G. J., Wiedner, U., Wilhelmi, Z., Wolke, M., Yamamoto, A., Yamaoka, H., Zabierowski, J., Zartova, I., and Złomańczuk, J.

Subjects
Nuclear Experiment
Abstract

The WASA 4pi multidetector system, aimed at investigating light meson production in light ion collisions and eta meson rare decays at the CELSIUS storage ring in Uppsala is presented. A detailed description of the design, together with the anticipated and achieved performance parameters are given., Comment: 25 pages, 20 figures

Published
2008
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15. Single- and Double-Pion Production in Nucleon Collisions on the Nucleon and on Nuclei -- the ABC Effect and its Possible Origin in a Dibaryonic Resonance

Author

Clement, H., Bashkanov, M., Doroshkevich, E., Khakimova, O., Kren, F., Pricking, A., Skorodko, T., and Wagner, G. J.

Subjects
Nuclear Experiment
Abstract

The ABC effect -- an intriguing low-mass enhancement in the $\pi\pi$ invariant mass spectrum -- is known from inclusive measurements of two-pion production in nuclear fusion reactions. First exclusive measurements carried out at CELSIUS-WASA for the fusion reactions leading to d or $^3$He reveal this effect to be a $\sigma$ channel phenomenon associated with the formation of a $\Delta\Delta$ system in the intermediate state and combined with a resonance-like behavior in the total cross section. Together with the observation that the differential distributions do not change in shape over the resonance region the features fulfill the criteria of an isoscalar s-channel resonance in $pn$ and $NN\pi\pi$ systems, if the two emitted nucleons are bound. It obviously is robust enough to survive in nuclei as a dibaryonic resonance configuration. In this context also the phenomenon of $N\Delta$ resonances is reexamined., Comment: 8 pages,3 figures, Proc. Int. School Nucl. Phys., 29th course on Quarks in Hadrons and Nuclei, Erice 2007 (to be published in Progress in Particle and Nuclear Physics)

Published
2007
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16. Two-Pion Production in Nucleon-Nucleon Collisions and the ABC-Effect - Approaching a Puzzleby exclusive and Kinematically complete Measurements

Author

Skorodko, T., Bashkanov, M., Bargholtz, C., Bogoslawsky, D., Calen, H., Cappellaro, F., Clement, H., Demiroers, L., Doroshkevich, E., Duniec, D., Ekstrom, C., Fransson, K., Geren, L., Hoistad, L. Gustafsson. B., Ivanov, G., Jacewicz, l M., Jiganov, E., Johansson, T., Kaskulov, M., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupsc, A., Kuznetsov, A., Lindberg, K., Marciniewski, P., Martemyanov, B., Meier, R., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Pricking, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Shwartz, B., Sopov, V., Stepaniak, J., Tegner, P. -E., Thorngren-Engholm, P., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

The ABC effect - a puzzling low-mass enhancement in the $\pi\pi$ invariant mass spectrum - is known from inclusive measurements of two-pion production in nuclear collisions, where it always showed up, if the participating nucleons fused to a bound nuclear system in the final state. The first exclusive measurements on the ABC effect have been carried out very recently at CELSIUS-WASA for the fusion reactions leading to d, $^3$He and $^4$He nuclei in the final state. The data analyzed so far for the fusion processes to d and $^3$He reveal this effect to be a $\sigma$ channel phenomenon associated with the formation of a strongly attractive $\Delta\Delta$ system. The data for the strictly isospin-selective double-pionic fusion to $^4$He, where we expect the largest effect, are currently still analyzed. All inclusive data on this system are well described by our model, too. This case also constitutes the heaviest nuclear system, where exclusive measurements of double-pionic fusion can be carried out with present-day instruments. Surprisingly, the $pp \to pp\pi^0\pi^0$ reaction in the $\Delta\Delta$ region is observed to also show a ABC-like low-$\pi\pi$ mass enhancement, a phenomenon, which deserves special attention.

Published
2006

17. Evidence for a 'Narrow' Roper Resonance - the Breathing Mode of the Nucleon

Author

Clement, H., Skorodko, T., Bashkanov, M., Bogoslawsky, D., Calen, H., Cappellaro, F., Demiroers, L., Doroshkevich, E., Ekstrom, C., Fransson, K., Hoistad, L. Gustafsson. B., Ivanov, G., Jacewicz, l M., Jiganov, E., Johansson, T., Kaskulov, M., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupsc, A., Kuznetsov, A., Marciniewski, P., Martemyanov, B., Meier, R., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Shwartz, B., Sopov, V., Stepaniak, J., Thorngren-Engholm, P., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., and Zlomanczuk, J.

Subjects
Nuclear Experiment
Abstract

All the time since its discovery the N$^*$(1440) baryon state, commonly known as Roper resonance, has been a state with many question marks - despite of its 4-star ranking in the particle data book. One reason is that it does not produce any explicit resonance-like structures in the observables of $\pi$N or $\gamma$N reactions. Only in partial wave analyses of $\pi$N scattering data a clear resonance strcuture gets obvious in the $P_{11}$ partial wave. Very recent measurements of the J/$\Psi$ decay by the BES collaboration and of the $pp \to np\pi^+$ reaction at 1.3 GeV by the CELSIUS-WASA collaboration show for the first time a clear resonance structure in the invariant $n\pi^+$ mass spectrum for the Roper resonance at M $\approx$ 1360 MeV with a width of about 150 MeV. These values agree very favorably with the pole position results of recent $\pi$N phase shift analyses. In consequence of this very low-lying pole postion, which is roughly 100 MeV below the nominal value, the decay properties have to be reinvestigated. From our two-pion production data we see that the decay mainly proceeds via N$^* \to $N$\sigma$, i.e. a monopole transition as expected for the breathing mode of the nucleon., Comment: CRIMEA06

Published
2006

18. Anisotropy in the pion angular distribution of the reaction pp -> pp pi0 at 400 MeV

Author

Engblom, P. Thorngren, Keleta, S. Negasi, Cappellaro, F., Hoistad, B., Jacewicz, M., Johansson, T., Koch, I., Kullander, S., Pettersson, H., Schonning, K., Zlomanczuk, J., Calen, H., Fransson, K., Kupsc, A., Marciniewski, P., Wolke, M., Pauly, C., Demirors, L., Scobel, W., Stepaniak, J., Zabierowski, J., Bashkanov, M., Clement, H., Khakimova, O., Kren, F., and Skorodko, T.

Subjects
Nuclear Experiment
Abstract

The reaction pp -> pp pi0 was studied with the WASA detector at the CELSIUS storage ring. The center of mass angular distribution of the pi0 was obtained by detection of the gamma decay products together with the two outgoing protons, and found to be anisotropic with a negative second derivative slope, in agreement with the theoretical predictions from a microscopic calculation., Comment: Revtex 4 style, 5 pages 7 figures, PACS numbers:13.60.Le, 13.75.Cs, 21.45.+v, 25.10.+s

Published
2006
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19. 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
Nuclear Theory, High Energy Physics::Experiment, ddc:530, Nuclear Experiment, 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
2012

20. Exclusive measurement of the η→ $\pi^+ \pi^-$ γ decay

Author

Adlarson, P., Adolph, C., Büscher, M., Szczurek, A., Täschner, A., Terschlüsen, C., Tolba, T., Trzciński, A., Varma, R., Vlasov, P., Wagner, G. J., Węglorz, W., Winnemöller, A., Calén, H., Wirzba, A., Wolke, M., Wrońska, A., Wüstner, P., Wurm, P., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, M. J., Clement, H., Zipper, W., Złomańczuk, J., Żuprański, P., Coderre, D., Czerwiński, E., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Augustyniak, W., Föhl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Grigoryev, K., Gullström, C.-O., Hanhart, C., Heijkenskjöld, L., Heimlich, J., Hejny, V., Bardan, W., Hinterberger, F., Hodana, M., Höistad, B., Jacewicz, M., Jany, A., Jany, B. R., Jarczyk, L., Johansson, T., Kamys, B., Kemmerling, G., Bashkanov, M., Khakimova, O., Khoukaz, A., Kistryn, S., Klaja, J., Kleines, H., Kłos, B., Kren, F., Krzemień, W., Kulessa, P., Kupść, A., Bednarski, T., Lalwani, K., Leupold, S., Lorentz, B., Magiera, A., Maier, R., Mariański, B., Marciniewski, P., Meißner, U.-G., Mikirtychiants, M., Morsch, H.-P., Bergmann, F. S., Moskal, P., Nandi, B. K., Niedźwiecki, S., Ohm, H., Passfeld, A., Pauly, C., Perez del Rio, E., Petri, T., Petukhov, Y., Piskunov, N., Berłowski, M., Pluciński, P., Podkopał, P., Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., Pyszniak, A., Rausmann, T., Redmer, C. F., Ritman, J., Bhatt, H., Roy, A., Rudy, Z., Sawant, S., Schadmand, S., Schmidt, A., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Brinkmann, K.-T., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Sterzenbach, G., Stockhorst, H., Stollenwerk, F., and Ströher, H.

Subjects
hadroproduction [eta], +helium+eta%22">p deuteron --> helium eta, gauge [invariance], Juelich COSY PS, momentum [beam], energy spectrum [photon], radiative decay [eta], 1.7 GeV/c, vector [form factor], (pi+ pi- photon) [mass spectrum], angular distribution [pi], High Energy Physics::Experiment, ddc:530, +pi%2B+pi-+photon%22">eta --> pi+ pi- photon, Nuclear Experiment, fusion [p deuteron], experimental results
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.

Published
2012

21. Exclusive measurement of the $\eta \rightarrow \pi^{+} \pi^{-} \gamma$ decay

Author

Adlarson, P., Adolph, C., Augustyniak, W., Bardan, Wiktor, Bashkanov, M., Bednarski, Tomasz, Bergmann, F. S., Berłowski, M., Bhatt, H., Brinkmann, K.-T., Büscher, M., Calén, H., Clement, H., Coderre, D., Czerwiński, Eryk, 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, Małgorzata, Höistad, B., Jacewicz, M., Jany, Anna, Jany, Benedykt, Jarczyk, Lucjan, Johansson, T., Kamys, Bogusław, Kemmerling, G., Khakimova, O., Khoukaz, A., Kistryn, Stanisław, Klaja, Joanna, Kleines, H., Kłos, B., Kren, F., Krzemień, Wojciech, Kulessa, P., Kupść, A., Lalwani, K., Leupold, S., Lorentz, B., Magiera, Andrzej, Maier, R., Mariański, B., Marciniewski, P., Meißner, U.-G., Mikirtychiants, M., Morsch, H.-P., Moskal, Paweł, Nandi, B. K., Niedźwiecki, Szymon, Ohm, H., Passfeld, A., Pauly, C., Perez del Rio, Elena, Petri, T., Petukhov, Y., Piskunov, N., Pluciński, P., Podkopał, Paweł, Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., Pyszniak, Andrzej, Rausmann, T., Redmer, C. F., Ritman, J., Roy, A., Rudy, Zbigniew, Sawant, S., Schadmand, S., Schmidt, A., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Skurzok, Magdalena, Smyrski, Jerzy, Sopov, V., Stassen, R., Stepaniak, J., Sterzenbach, G., Stockhorst, H., Stollenwerk, F., Ströher, H., 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, Aleksandra, Wüstner, P., Wurm, P., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, Marcin, Zipper, W., Złomańczuk, J., and Żuprański, P.

Subjects
box anomaly, exclusive measurement, High Energy Physics::Experiment, $\eta$ meson, Nuclear Experiment
Abstract

An exclusive measurement of the decay $\eta \rightarrow \pi^{+} \pi^{-} \gamma$ has been performed at the WASA facility at COSY. The $\eta$ mesons were produced in the fusion reaction $pd \rightarrow ^{3}He X$ at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13 960 $\pm$ 140 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 $\eta \rightarrow \pi^{+} \pi^{-} \gamma$. 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.

Published
2012

22. ��^0 ��^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., Ber��owski, M., Bhatt, H., Brinkmann, K. --T., B��scher, M., Cal��n, H., Clement, H., Coderre, D., Czerwi��ski, E., Doroshkevich, E., Engels, R., Erven, W., Eyrich, W., Fedorets, P., F��hl, K., Fransson, K., Goldenbaum, F., Goslawski, P., Grigoryevj, K., Gullstr��m, C. --O., Heijkenskj��ld, L., Heimlich, J., Hejny, V., Hinterberger, F., Hodana, M., H��istad, 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., K��os, B., Kren, F., Krzemie��, W., Kulessa, P., Kup����, A., Lalwani, K., Lorentz, B., Machner, H., Magiera, A., Maier, R., Maria��ski, B., Marciniewski, P., Mikirtychiants, M., Morsch, H. --P., Moskal, P., Nandi, B. K., Nied��wiecki, S., Ohm, H., Passfeld, A., Pauly, C., del Rio, E. Perez, Petukhov, Y., Piskunov, N., Pluci��ski, P., Podkopa��, 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., T��schner, A., Tolba, T., Trzci��ski, A., Varma, R., Vlasov, P., Wagner, G. J., Weglorz, W., Wiedner, U., Winnem��ller, A., Wolke, M., Wro��ska, A., W��stner, P., Wurm, P., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieli��ski, M. J., Zipper, W., Z��oma��czuk, J., and Zupra��ski, P.

Subjects
High Energy Physics - Experiment (hep-ex), Nuclear Theory, FOS: Physical sciences, High Energy Physics::Experiment, Nuclear 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, Submitted to PLB

Published
2011
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23. Exclusive Measurements of pp to dpi+pi0: Double-Pionic Fusion without ABC Effect

Author

Kren, F., Bashkanov, M., Bogoslawsky, D., Calen, H., Clement, H., Demiroers, L., Ekstrom, C., Fransson, k., Greiff, J., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Kohansson, T., Khakimova, O., Keleta, S., Koch, I., Kullander, S., Kupsc, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petren, H., Petukhov, Y., Povtoreijko, A., Ruber, R. J. M. Y., Schonning, K., Scobel, W., Skorodko, T., Shwartz, B., Stepaniak, J., Thorngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., and Zlomanczuk, J.

Subjects
exclusive reaction [p p], fusion, Dalitz plot, isovector, four-pi-detector, energy dependence [channel cross section], +deuteron+pi%2B+pi0%22">p p --> deuteron pi+ pi0, Delta(1232), Uppsala CELSIUS Stor, mass spectrum, pair production [pi], High Energy Physics::Experiment, ddc:530, Nuclear Experiment
Abstract

Exclusive measurements of the reaction pp -> dpi+pi0 have been carried out at T_p = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector pi+pi0 channel exhibits no enhancement at low invariant pipi masses, i. e. no ABC effect. The differential distributions are in agreement with the conventional t-channel Delta-Delta excitation process, which also accounts for the observed energy dependence of the total cross section. This is an update of a previously published version -- see important note at the end of the article.

Published
2011

24. The pd --> ^3He eta pi0 reaction at T_p = 1450 MeV

Author

Schoenning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demiroers, L., Ekstroem, C., Fransson, K., Geren, L., Gustafsson, L., Hoeistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. -E., Thoerngren-Engblom, P., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, Jozef

Subjects
ddc:530, Nuclear Experiment
Abstract

The cross section for the pd --> ^3He eta pi0 reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring and detecting one ^3He and four photons from the decays of the two photons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant masses of all three pairs of final state particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi^0 momentum in the ^3Hepi^0 system., Comment: 10 pages, 5 figures

Published
2010

25. Measurement of the eta -> 3 pi(0) Dalitz plot distribution with the WASA detector at COSY

Author

ADOLPH, C, ANGELSTEIN, M, BASHKANOV, M, BECHSTEDT, U, BELOSTOTSKI, S, BERLOWSKI, M, BHATT, H, BISPLINGHOFF, J, BONDAR, A, BORASOY, B, BUSCHER, M, SCOBEL, W, SEFZICK, T, SERDYUK, V, SHAH, N, SIEMASZKO, M, SIUDAK, R, SKORODKO, T, SMOLINSKI, T, SMYRSKI, J, SOPOV, V, CALEN, H, SPOLGEN, D, STEPANIAK, J, STERZENBACH, G, STROHER, H, SZCZUREK, A, TEUFEL, A, TOLBA, T, TRZCINSKI, A, ULBRICH, K, VARMA, R, CHANDWANI, K, VLASOV, P, WEGLORZ, W, WINNEMOLLER, A, WIRZBA, A, WOLKE, M, WRONSKA, A, WUSTNER, R, XU, H, YAMAMOTO, A, YAMAOKA, H, CLEMENT, H, YUAN, X, YUREV, L, ZABIEROWSKI, J, ZHENG, C, ZIELINSKI, MJ, ZIPPER, W, ZLOMANCZUK, J, ZWOLL, K, ZYCHOR, I, CZERWINSKI, E, CZYZYKIEWICZ, R, D'ORSANEO, G, DUNIEC, D, EKSTROM, C, ENGELS, R, ERVEN, W, EYRICH, W, FEDORETS, P, FELDEN, O, FRANSSON, K, GIL, D, GOLDENBAUM, F, GRIGORYEV, K, HECZKO, A, HANHART, C, HEJNY, V, HINTERBERGER, F, HODANA, M, HOISTAD, B, IZOTOV, A, JACEWICZ, M, JANUSZ, M, JANY, BR, JARCZYK, L, JOHANSSON, T, KAMYS, B, KEMMERLING, G, KESHELASHVILI, I, KHAKIMOVA, O, KHOUKAZ, A, KILIAN, K, KIMURA, N, KISTRYN, S, KLAJA, J, KLAJA, P, KLEINES, H, KLOS, B, KOWALCZYK, A, KREN, F, KRZEMIEN, W, KULESSA, P, KULLANDER, S, KUPSC, A, KUZMIN, A, KYRYANCHUK, V, MAJEWSKI, J, MACHNER, H, MAGIERA, A, MAIER, R, MARCINIEWSKI, R, MIGDAL, W, MEISSNER, UG, MIKIRTYCHIANTS, M, MIKLUKHO, O, MILKE, N, MITTAG, M, MOSKAL, P, NANDI, BK, NAWROT, A, NISSLER, R, ODOYO, MA, OELERT, W, OHM, H, PAUL, N, PAULY, C, PETUKHOV, Y, PISKUNOV, N, PLUCINSKI, P, PODKOPAL, P, POVTOREYKO, A, PRASUHN, D, PRICKING, A, PYSZ, K, RACHOWSKI, J, RAUSMANN, T, REDMER, CF, RITMAN, J, ROY, A, RUBER, RJMY, RUDY, Z, SALMIN, R, SCHADMAND, S, SCHMIDT, A, SCHNEIDER, H, and SCHROEDER, W

Subjects
Current-Algebra, Performance, Dalitz plot, Nuclear Theory, hadronic decay [eta], 1.4 GeV, interaction [p p], final-state interaction [pi pi], Juelich COSY PS, +2p+eta%22">p p --> 2p eta, eta, Final-State Interactions, +3+pi%280%29%22">eta -> 3 pi(0), Chiral Perturbation-Theory, +3+Pi%280%29%22">Eta -> 3 Pi(0), Channels, 3-Pi%22">Eta->3-Pi, ddc:530, Nuclear Experiment, Daq System, hadroproduction [eta], Eta, Pi-Pi Scattering, Electromagnetic Corrections, slope [Dalitz plot], Dalitz Plot, High Energy Physics::Experiment, Decays, +3pi0%22">eta --> 3pi0
Abstract

In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pions was studied using 1.2e5 fully reconstructed events, and the quadratic slope parameter alpha was determined to be -0.027+/-0.008(stat)+/-0.005(syst). The result is consistent with previous measurements and further corroborates the importance of pion-pion final state interactions., Comment: 6 pages, 4 figures, elsarticle

Published
2009

26. Production of the omega meson in the pd -> He-3 omega reaction at 1450 MeV and 1360 MeV

Author

Schonning, K., Bargholtz, C., Bashkanov, M., Berlowski, M., Bogoslawsky, D., Calen, H., Clement, H., Demirors, L., Ekstrom, C., Fransson, K., Geren, L., Gustafsson, L., Hoistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Khemchandani, Kanchan P., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Petukhov, Y., Povtorejko, A., Ruber, Rjmy, Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, P. E., Engblom, P. T., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Zlomanczuk, J.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

The production of omega mesons in the pd -> He-3 omega reaction has been studied at two energies near the kinematic threshold, T-p = 1450 MeV and T-p = 1360 MeV. The differential cross section was measured as a function of the omega c.m. angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections., We wish to thank the personnel at the The Svedberg Laboratory for their support during the course of the experiment. We are grateful to Y. le Bornec for providing us with information regarding Ref. [5] and also V. Shklyar for supplying the t-matrix element of the Giessen model described in Ref. [31]. This work was supported by the European Community under the “Structuring the Research Area” Specific Program Research Infrastructures Action (Hadron Physics, contract no. RII-cT-204-506078) by the Swedish Research Council, and BMBF (06TU201). K.P.K. wishes to thank the Fundacao para a Ciˆencia e a Tecnologia of the Minist´erio da Ciˆencia, Tecnologia e Ensino Superior of Portugal for financial support under Contract No. SFRH/BPD/40309/2007.

Published
2009

27. Production of the meson in the pd3He reaction at 1450 MeV and 1360 MeV

Author

Schönning, K., Bargholtz, Chr., Geren, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Khemchandani, K., Bashkanov, M., Kren, F., Kullander, S., Kupsc, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petren, H., Berlowski, M., Petukhov, Y., Povtorejko, A., Ruber, R., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegner, E., Bogoslawsky, D., Thörngren-Engblom, P., Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., Zlomanczuk, J., Calen, H., Clement, H., Demirörs, L., Ekström, C., and Fransson, K.

Subjects
Nuclear Theory, ddc:530, Nuclear Experiment
Abstract

The production of omega mesons in the pd -> He-3 omega reaction has been studied at two energies near the kinematic threshold, T-p = 1450 MeV and T-p = 1360 MeV. The differential cross section was measured as a function of the omega c.m. angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections.

Published
2009

28. Exclusive Measurements of $pd\to ^3He \pi\pi$ : the $ABC$ Effect Revisited

Author

Bashkanov, M., Bogoslawsky, D., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Kaskulov, M. M., Keleta, S., Koch, I., Kren, F., Calen, H., Kullander, S., Kupsc, A., Kuznetsov, A., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pauly, C., Petukhov, Y., Povtorejko, A., Cappellaro, F., Ruber, R.J.M.Y., Scobel, W., Skorodko, T., Shwartz, B., Sopov, V., Stepaniak, J., Tchernyshev, V., Thörngren-Engblom, P., Tikhomirov, V., Turowiecki, A., Clement, H., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Zlomanczuk, J., Demiroers, L., Ekström, C., Fransson, K., Greiff, J., and Gustafsson, L.

Subjects
experimental results [four-pi-detector], two-pion [mass spectrum], pair production [pi], Dalitz plot, 0.893 GeV-cms, mass enhancement, ddc:530, angular distribution, +helium-3+pi%2B+pi%22">p deuteron --> helium-3 pi+ pi, Nuclear Experiment, exclusive reaction [p deuteron], Uppsala CELSIUS Stor, +helium-3+2pi0%22">p deuteron --> helium-3 2pi0
Abstract

Exclusive measurements of the reactions $pd\to$ $^3He \pi^+ \pi^-$ and $pd\to$ $^3He \pi^0\pi^0$ have been carried out at $T_p=0.895$ GeV at the CELSIUS storage ring using the WASA detector. The $\pi^+\pi^-$ channel evidences a pronounced enhancement at low invariant $\pi\pi$ masses - as anticipated from previous inclusive measurements of the ABC effect. This enhancement is seen to be even much larger in the isoscalar $\pi^0\pi^0$ channel. The differential distributions prove this enhancement to be of scalar-isoscalar nature. $\Delta\Delta$ calculations give a good description of the data, if a boundstate condition is imposed for the intermediate $\Delta\Delta$ system., Comment: extended version, 8 pages, 7 figures, theoretical model calculations added

Published
2005

29. Polarisation of the ω meson in the pd→He3ω reaction at 1360 and 1450 MeV

Author

Schönning, K., Bargholtz, Chr., Bashkanov, M., Berłowski, M., Bogoslawsky, D., Calén, H., Clement, H., Demirörs, L., Ekström, C., Fransson, K., Gerén, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Koch, I., Kren, F., Kullander, S., Kupść, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R.J.M.Y., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegnér, P.-E., Engblom, P. Thörngren, Tikhomirov, V., Turowiecki, A., Wagner, G.J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Złomańczuk, J.

Subjects
ω polarisation, ω meson production, High Energy Physics::Phenomenology, Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, OZI rule
Abstract

The tensor polarisation of ω mesons produced in the pd→He3ω reaction has been studied at two energies near threshold. The He3 nuclei were detected in coincidence with the π0π+π− or π0γ decay products of the ω. In contrast to the case of ϕ-meson production, the ω mesons are found to be unpolarised. This brings into question the applicability of the Okubo–Zweig–Iizuka rule when comparing the production of vector mesons in low energy hadronic reactions.

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30. π0π0 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., Grigoryev, 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., 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., Perez del Rio, E., Petukhov, Y., Piskunov, N., Pluciński, P., Podkopał, P., Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., 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., Skorodko, T., Skurzok, M., Smyrski, J., Sopov, V., Stassen, R., Stepaniak, J., Sterzenbach, G., Stockhorst, H., Ströher, H., Szczurek, A., Täschner, A., Tolba, T., Trzciński, A., Varma, R., Vlasov, P., Wagner, G.J., Węglorz, 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 Żuprański, P.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment
Abstract

The reaction pp→ppπ0π0 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±21systematic±58normalization) μb. In order to study the production mechanism, differential kinematic distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Δ(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.

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31. The pd→He3ηπ0 reaction at Tp=1450 MeV

Author

Schönning, K., Bargholtz, Chr., Bashkanov, M., Berłowski, M., Bogoslawsky, D., Calén, H., Clement, H., Demirörs, L., Ekström, C., Fransson, K., Gerén, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Khakimova, O., Kren, F., Kullander, S., Kupść, A., Kuzmin, A., Lindberg, K., Marciniewski, P., Morosov, B., Oelert, W., Pauly, C., Petrén, H., Petukhov, Y., Povtorejko, A., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegnér, P.-E., Thörngren Engblom, P., Tikhomirov, V., Turowiecki, A., Wagner, G.J., Wilkin, C., Wolke, M., Zabierowski, J., Zartova, I., and Złomańczuk, J.

Subjects
η, π0 meson production, Nuclear Experiment, Invariant-mass distribution, Δ resonance
Abstract

The cross section for the pd→He3ηπ0 reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring. The 3He was detected in coincidence with four photons from the decays of the two mesons. The data indicate that the production mechanism involves the formation of the Δ(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant mass distributions of all three pairs of final particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the π0 momentum in the He3π0 system.

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