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194 results on '"Povtorejko, A"'

1. 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

2. 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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3. 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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4. 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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5. 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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6. 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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7. 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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8. 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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9. 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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10. 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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11. Measurement of eta meson decays into lepton-antilepton pairs

Author

Collaboration, CELSIUS/WASA, Berłowski, M., Bargholtz, Chr., Bashkanov, M., Bogoslawsky, D., Bondar, A., Calén, H., Cappellaro, F., Clement, H., Demirörs, L., Ekström, C., Fransson, K., Gerén, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Koch, I., Kullander, S., Kupść, A., Kuzmin, A., Kuznetsov, A., Laukhin, I. V., Lindberg, K., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Schönning, K., 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., Wolke, M., Yamamoto, A., Zabierowski, J., Zartova, I., and Złomańczuk, J.

Subjects
High Energy Physics - Experiment
Abstract

A search for rare lepton decays of the eta meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay eta->e+e-e+e- events are reported with a background of 1.3+/-0.2 events. This allows to set an upper limit to the branching ratio of 9.7E-5 (90% CL). The branching ratio for the decay eta->e+e-gamma is determined to (7.8+/-0.5 stat+/-0.8 syst)E-3. An upper limit (90% CL) for the branching ratio for the eta->e+e- decay is 2.7E-5 and a limit for the sum of the eta->mu+mu-mu+mu- and eta->pi+pi-mu+mu- decays is 3.6E-4., Comment: 9 pages, 10 Postscript figures, uses revtex4.sty, revised version after referee comments; conclusions unchanged

Published
2007
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12. Measurement of the Slope Parameter for the eta->3pi0 Decay in the pp->pp eta Reaction

Author

Bashkanov, M., Bogoslawsky, D., Calén, H., Capellaro, F., Clement, H., Demirörs, L., Ekström, C., Fransson, K., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Koch, I., Kullander, S., Kupsc, A., Kuznetsov, A., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pauly, C., Petukhov, Y., Pettersson, H., Povtorejko, A., Ruber, R. J. M. Y., Schönning, K., Scobel, W., Skorodko, T., Shwartz, B., Sopov, V., Stepaniak, J., Tchernyshev, V., Engblom, P. Thörngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wiedner, U., Wolke, M., Yamamoto, A., Zabierowski, J., and Złomańczuk, J.

Subjects
Nuclear Experiment
Abstract

The CELSIUS/WASA setup is used to measure the 3pi0 decay of eta mesons produced in pp interactions with beam kinetic energies of 1.36 and 1.45 GeV. The efficiency-corrected Dalitz plot and density distributions for this decay are shown, together with a fit of the quadratic slope parameter alpha yielding alpha = -0.026 +/- 0.010(stat) +/- 0.010(syst). This value is compared to recent experimental results and theoretical predictions., Comment: 4 pages, 7 Postscript figures, uses revtex4.sty

Published
2007
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13. 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

14. 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

15. Measurement of the eta->pi+pi-e+e- decay branching ratio

Author

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

Subjects
High Energy Physics - Experiment
Abstract

The reaction pd->3He eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta->pi+pi-e+e- is measured to be (4.3+/-1.3+/-0.4)x10^-4., Comment: 10 pages,6 figures revised version

Published
2006
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16. The pp -> pp pi pi pi reaction channels in the threshold region

Author

Collaboration, CELSIUS-WASA, Pauly, C., Jacewicz, M., Koch, I., Bashkanov, M., Bogoslawsky, D., Calén, H., Capellaro, F., Clement, H., Demirörs, L., Ekström, C., Fransson, K., Gustafsson, L., Höistad, B., Ivanov, G., Jiganov, E., Johansson, T., Keleta, S., Kullander, S., Kupść, A., Kuznetsov, A., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Scobel, W., Schönning, K., Skorodko, T., Shwartz, B., Sopov, V., Stepaniak, J., Tchernyshev, V., Engblom, P. Thörngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wiedner, U., Wolke, M., Yamamoto, A., Zabierowski, J., and Złomańczuk, J.

Subjects
Nuclear Experiment
Abstract

The cross section for prompt neutral and charged three pion production in pp interactions was measured at excess energies in the range 160 - 217 MeV. That comprises the first measurement of the pp->pp pi0pi0pi0 reaction and the comparison with the pp->pp pi+pi-pi0 reaction, in a very direct way. The experiment was performed above the eta meson production threshold and the cross section normalization was obtained from a concurrent measurement of the reaction pp->pp eta with the eta decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio sigma(pp->pp pi+pi-pi0)/sigma(pp->pp pi0\pi0\pi0) is compared to predictions of dominance of different isobars in the intermediate state., Comment: 12 pages, 4 figures New discussion on the pp->pp3pi reaction mechanism

Published
2006
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17. Exclusive Measurements of $pd\to ^3He \pi\pi$ : the $ABC$ Effect Revisited

Author

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

Subjects
Nuclear Experiment
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
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18. Higher Partial Waves in p+p->p+p+eta near Threshold

Author

Calen, H., Dyring, J., Faldt, G., Fransson, K., Gustafsson, L., Haggstrom, S., Hoistad, B., Johanson, J., Johansson, A., Johansson, T., Kullander, S., Mortsell, A., Ruber, R., Zlomanczuk, J., Ekstrom, C., Kilian, K., Oelert, W., Sefzick, T., Bilger, R., Brodowski, W., Clement, H., Wagner, G. J., Bondar, A., Kuzmin, A., Shwartz, B., Sidorov, V., Sukhanov, A., Dunin, V., Morosov, B., Povtorejko, A., Zernov, A., Kupsc, A., Marciniewski, P., Stepaniak, J., Zabierowski, J., Turowiecki, A., Wilhelmi, Z., and Wilkin, C.

Subjects
Nuclear Experiment
Abstract

Exclusive measurements of the production of eta mesons in the p+p->p+p+eta reaction have been carried out at excess energies of 16 and 37 MeV above threshold. The deviations from phase space are dominated by the proton-proton final state interaction and this influences particularly the energy distribution of the eta meson. However, evidence is also presented at the higher energy for the existence of an anisotropy in the angular distributions of the eta meson and also of the final proton-proton pair, probably to be associated with D-waves in this system interfering with the dominant S-wave term. The sign of the eta angular anisotropy suggests that rho-exchange is important for this reaction., Comment: 16 pages, LaTeX2e, 3 EPS Figures, Updated version, Accepted for publication in Phys. Lett. B

Published
1998
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19. Excitation of the Roper resonance in single- and double-pion production in nucleon-nucleon collisions

Author

The CELSIUS-WASA Collaboration, Skorodko, T., Bashkanov, M., Bogoslawsky, D., Calen, H., Cappellaro, F., Clement, H., Demiroers, L., Doroshkevich, E., Duniec, D., Ekström, C., Franssen, K., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Kaskulov, M., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupść, A., Kuznetsov, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petterson, H., Petukhov, Y., Povtorejko, A., Schönning, K., Scobel, W., Shwartz, B., Sopov, V., Stepeniak, J., Thörngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Złomanczuk, J., Hammer, Hans-Werner, editor, Kleber, Vera, editor, Thoma, Ulrike, editor, and Schmieden, Hartmut, editor

Published
2008
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20. Meson Production Near Threshold

Author

Johansson, Tord, Calén, H., Dyring, J., Fransson, K., Gustafsson, L., Häggström, S., Höistad, B., Johanson, J., Johansson, A., Kullander, S., Ruber, R. J. M. Y., Zlomanczuk, J., Ekström, C., Kilian, K., Oelert, W., Sefsick, T., Bilger, R., Brodowski, W., Clement, H., Wagner, G. J., Bondar, A., Shwartz, B., Sidorov, V., Sukhanov, A., Kupsc, A., Marciniewski, P., Stepaniak, J., Zabierowski, J., Dunin, V., Morosov, B., Povtorejko, A., Zernov, A., Turowiecki, A., Wilhelmi, Z., Sopov, V., Tchernychev, T., Smit, F. D., editor, Lindsay, R., editor, and Förtsch, S. V., editor

Published
1999
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21. Exclusive measurement of the pp → nnπ+π+ reaction at 1.1 GeV

Author

Skorodko, T., Bashkanov, M., Bogoslawsky, D., Calén, H., Clement, H., Doroshkevich, E., Demiroers, L., Ekström, C., Fransson, K., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupść, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petrén, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Schönning, K., Scobel, W., Shwartz, B., Stepaniak, J., Thörngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Zlomanczuk, J., and The CELSIUS/WASA Collaboration

Published
2011
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22. Single- and double-pion production in nucleon collisions on the nucleon and on nuclei—the ABC effect and its origin in a dibaryonic resonance

Author

Clement, H., Bashkanov, M., Bargholtz, C., Bogoslawsky, D., Calen, H., Cappellaro, F., Demiroers, L., Doroshkevich, E., Duniec, D., Ekström, C., Franssen, K., Geren, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Kaskulov, M., Khakimova, O., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupść, A., Kuznetsov, A., Lindberg, K., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petterson, H., Petukhov, Y., Povtorejko, A., Pricking, A., Schönning, K., Scobel, W., Shwartz, B., Skorodko, T., Sopov, V., Stepeniak, J., Tegner, P.-E., Thörngren-Engblom, P., Tikhomirov, V., Wagner, G.J., Wolke, M., Yamamoto, A., Zabierowski, J., Zartova, I., and Złomanczuk, J.

Published
2008
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23. Excitation of the Roper resonance in single- and double-pion production in nucleon-nucleon collisions⋆

Author

Skorodko, T., Bashkanov, M., Bogoslawsky, D., Calen, H., Cappellaro, F., Clement, H., Demiroers, L., Doroshkevich, E., Duniec, D., Ekström, C., Franssen, K., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Khakimova, O., Kaskulov, M., Keleta, S., Koch, I., Kren, F., Kullander, S., Kupść, A., Kuznetsov, A., Marciniewski, P., Meier, R., Morosov, B., Pauly, C., Petterson, H., Petukhov, Y., Povtorejko, A., Schönning, K., Scobel, W., Shwartz, B., Sopov, V., Stepeniak, J., Thörngren-Engblom, P., Tikhomirov, V., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Złomanczuk, J., and The CELSIUS-WASA Collaboration

Published
2008
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24. Meson Production Near Threshold

Author

Johansson, Tord, primary, Calén, H., additional, Dyring, J., additional, Fransson, K., additional, Gustafsson, L., additional, Häggström, S., additional, Höistad, B., additional, Johanson, J., additional, Johansson, A., additional, Kullander, S., additional, Ruber, R. J. M. Y., additional, Zlomanczuk, J., additional, Ekström, C., additional, Kilian, K., additional, Oelert, W., additional, Sefsick, T., additional, Bilger, R., additional, Brodowski, W., additional, Clement, H., additional, Wagner, G. J., additional, Bondar, A., additional, Shwartz, B., additional, Sidorov, V., additional, Sukhanov, A., additional, Kupsc, A., additional, Marciniewski, P., additional, Stepaniak, J., additional, Zabierowski, J., additional, Dunin, V., additional, Morosov, B., additional, Povtorejko, A., additional, Zernov, A., additional, Turowiecki, A., additional, Wilhelmi, Z., additional, Sopov, V., additional, and Tchernychev, T., additional

Published
2000
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25. Exclusive measurements of pp→dπ+π0: Double-pionic fusion without ABC effect

Author

Curt Ekstrom, Bo Höistad, R. J. M. Y. Ruber, P. Thörngren-Engblom, Magnus Wolke, B. Morosov, M. Bashkanov, Jozef Zlomanczuk, Andrzej Kupsc, B. Shwartz, J. Stepaniak, S. Keleta, I. Koch, O. Khakimova, V. Tikhomirov, Karin Schönning, P. Marciniewski, G. J. Wagner, Y. Petukhov, L. Demiroers, E. Jiganov, F. Kren, H. Clement, D. Bogoslawsky, Sven Kullander, J. Zabierowski, Leif Gustafsson, A. Povtorejko, Marek Jacewicz, Akira Yamamoto, G. Ivanov, Hans Calén, Tord Johansson, W Scobel, K. Fransson, Henrik Petrén, T. Skorodko, J. Greiff, R. Meier, and C. Pauly

Subjects
Nuclear physics, Physics, Nuclear and High Energy Physics, Fusion, Isovector, Pi
Abstract

Exclusive measurements of the reaction pp -> d pi(+)pi(0) have been carried out at T-p = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector pi(+)pi(0) channel exhibits no ...

Published
2010
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26. ISOSPIN DECOMPOSITION OF pp → NNππ CROSS SECTIONS — DO WE SEE A SIGN OF Δ(1600) EXCITATION IN THE nnπ+π+ CHANNEL?

Author

Andrzej Kupsc, Pawel Marciniewski, V. Tikhomirov, Henrik Petterson, P. Thörngren-Engblom, A. A. Kuznetsov, Sven Kullander, E. Jiganov, Karin Schönning, H. Clement, A. Povtorejko, A. Turowiecki, M. Wolke, Hans Calén, B. Morosov, Jozef Zlomanczuk, M. Bashkanov, Kjell Fransson, B. Shwartz, J. Stepaniak, Bo Höistad, G. Ivanov, Y. Petukhov, J. Zabierowski, G. J. Wagner, Wolfgang Scobel, Tord Johansson, Curt Ekstrom, R. Meier, V. Sopov, F. Kren, Marek Jacewicz, C. Pauly, S. Keleta, D. Bogoslowsky, Akira Yamamoto, Roger Ruber, T. Skorodko, I. Koch, O. Khakimova, and Leif Gustafsson

Subjects
Delta, Physics, Nuclear and High Energy Physics, Particle physics, Astronomy and Astrophysics, Decomposition, Resonance (particle physics), Atomic and Molecular Physics, and Optics, Nuclear physics, Cross section (geometry), Isospin, Pi, Excitation, Sign (mathematics)
Abstract

The two-pion production in pp-collisions has been investigated in exclusive measurements from threshold up to Tp = 1.36 GeV . Total and differential cross sections have been obtained for the channels pnπ+π0, ppπ+π-, ppπ0π0 and also nnπ+π+. For intermediate incident energies Tp > 1 GeV , i.e. in the region, which is beyond the Roper excitation but at the onset of ΔΔ excitation the total ppπ0π0 cross section falls behind theoretical predictions by as much as an order of magnitude near 1.2 GeV, whereas the nnπ+π+ cross section is a factor of five larger than predicted. A model-unconstrained isospin decompostion of the cross section points to a significant contribution of an isospin 3/2 resonance other than the Δ(1232). As a possible candidate the Δ(1600) is discussed.

Published
2009
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27. ππ PRODUCTION IN PROTON-PROTON COLLISIONS

Author

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

Subjects
Physics, Nuclear and High Energy Physics, Fusion, Complete data, Range (particle radiation), Proton, Excited state, Astronomy and Astrophysics, Invariant mass, Production (computer science), Atomic physics, Atomic and Molecular Physics, and Optics, Excitation
Abstract

At CELSIUS-WASA the two-pion production in proton-proton collisisons has been measured exclusively from threshold up to the energy regime, where both of the collision partners are expected to be excited to the Δ state. The measurements constitute the first kinematically complete data samples of solid statistics in this energy range. Most of the data have been obtained for the π+π- and π0π0channels. Whereas at near-threshold energies the differential distributions can be succesfully explained by chiral dynamics and Roper excitation, respectively, the data for the π+π- channel in the ΔΔ region can be described only, if the special configuration (ΔΔ)0+ is assumed. The data for the π0π0 channel moreover exhibit a low-mass enhancement in the π0π0 invariant mass spectrum, which is reminiscent of the ABC-effect found in double-pionic fusion to light nuclei.

Published
2007
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28. TWO-PION PRODUCTION, γγ LINE AND ASPECTS OF σ MESON, BOSE–EINSTEIN CORRELATIONS AND ISOSPIN BREAKING

Author

T. Johansson, D. Bogoslawsky, Jozef Zlomanczuk, C. Ekström, Akira Yamamoto, A. Kupść, E. Jiganov, P. Thörngren Engblom, G. J. Wagner, H. Clement, O. Khakimova, K. Fransson, W. Oelert, Leif Gustafsson, E. Doroshkevich, S. Kullander, G. Ivanov, Marek Jacewicz, J. Zabierowski, R. Meier, T. Skorodko, S. Keleta, F. Cappellano, L. Demiroers, V. Tchernyshev, Bo Höistad, M. Kaskulov, V. Sopov, F. Kren, C. Pauly, J. Greiff, A. N. Kuznetsov, B. Morosow, Pawel Marciniewski, R. J. M. Y. Ruber, I. Koch, Hans Calén, M. Bashkanov, Ulrich Wiedner, W. Scobel, A. Turowiecki, Magnus Wolke, V. Tikhomirov, J. Stepaniak, Y. Petukhov, B.A. Shwartz, and A. Povtorejko

Subjects
Physics, Nuclear and High Energy Physics, Roper resonance, Particle physics, Hydrogen, Meson, chemistry.chemical_element, Astronomy and Astrophysics, Bose–Einstein correlations, Invariant (physics), Atomic and Molecular Physics, and Optics, Nuclear physics, Pion, chemistry, Isospin, Hermetic detector
Abstract

The pp→ppx(x=γγ, π0π0, π+π-) reactions have been measured at CELSIUS in the energy range Tp=775-1360 MeV using the WASA 4π detector with hydrogen pellet target. Close to threshold the ppπ+π- data are in accordance with the Roper resonance concept and/or a dynamic formation of the σ meson. At higher energies the formation of the ΔΔ system becomes increasingly dominant. The ppπ0π0 channel basically shows similar features, however, develops a peculiar enhancement at small invariant masses Mπ0π0 - in resemblance of Bose-Einstein correlations. Alternatively, the enhancement could be also indicative of a (dynamic) isospin breaking due to ππ rescattering in the σ channel. The latter is favored by the results on pd→3 He x (x=π0π0, π+π-), where the observed π0π0 enhancements are still much larger. In the γγ channel a line at Mγγ=2mπ is observed. The possible nature of this line is discussed.

Published
2005
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29. First results from the CELSIUS/WASA facility

Author

Z. Wilhelmi, V. Tchernyshev, V. Tikhomirov, P.-E. Tegnér, L. Gustafsson, N. Kimura, R. Shafigulin, D. Reistad, M. Bashkanov, K. Lindberg, J. Zabierowski, D. Bogoslawsky, J. Greiff, A. Nawrot, C. Bargholz, Arne Johansson, P. Marciniewski, T. Skorodko, S. Keletea, H. Yamaoka, Hans Calén, H. Clement, L. Demiroers, Y. Petukhov, Bo Höistad, A. Kipsc, F. Cappellaro, S. Kullander, B.A. Shwartz, Kjell Fransson, W. Oelert, Tord Johansson, S. Sandukovsky, B. M. K. Nefkens, V. Sopov, J. Zlomanczuk, A. Povtorejko, E. Jiganov, Ulrich Wiedner, W. Scobel, Marek Jacewicz, E. Dorochkevitch, Curt Ekstrom, I. Koch, Roger Ruber, B. Morosov, P. Thörngren Engblom, J. Stepaniak, G.J. Wagner, M. Gornov, Akira Yamamoto, A. Turowiecki, G. Ivanov, C. Pauly, A. A. Kuznetsov, and C.-J. Fridén

Subjects
Physics, Nuclear and High Energy Physics, Degree Celsius, Nuclear engineering
Published
2003
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30. Two-pion production in proton–proton collisions near threshold

Author

W. Oelert, J. Greiff, W. Brodowski, P. Marciniewski, B. Morosov, H. Clement, R. Bilger, S. Kullander, T. Sefzick, J. Johanson, Hans Calén, J. Stepaniak, A. Sukhanov, I. Koch, A. Khoukaz, Roger Ruber, Curt Ekstrom, Kjell Fransson, Arne Johansson, L. Gustafsson, S. Häggström, Bo Höistad, Tord Johansson, J. Zabierowski, J. Zlomanczuk, Andrzej Kupsc, W. Scobel, G.J. Wagner, B.A. Shwartz, and A. Povtorejko

Subjects
Nuclear reaction, Physics, Nuclear and High Energy Physics, Proton, Nuclear Theory, Detector, Nuclear physics, Near threshold, Pion, Cluster (physics), High Energy Physics::Experiment, Atomic physics, Nuclear Experiment, Storage ring
Abstract

Two-pion production reactions in proton-proton collisions have been studied using the PROMICE/WASA detector and an internal cluster gas-jet target at the CELSIUS storage ring in Uppsala. Three out ...

Published
2002
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31. THE pp → ppπ0π0 REACTION AND ITS LIMITING CASE, FUSION TO QUASI-BOUND 2<font>He</font>, IN SEARCH OF THE ABC EFFECT

Author

B. Morosov, Jozef Zlomanczuk, Leif Gustafsson, B. Shwartz, J. Stepaniak, V. Sopov, F. Kren, A. A. Kuznetsov, Wolfgang Scobel, A. Turowiecki, E. Jiganov, Karin Schönning, H. Clement, Magnus Wolke, Sven Kullander, Curt Ekstrom, G. Ivanov, G. J. Wagner, Henrik Petterson, Andrzej Kupsc, Bo Höistad, S. Negasi Keleta, E. Doroshkevich, A. Pricking, A. Povtorejko, R. Meier, Akira Yamamoto, Tord Johansson, T. Skorodko, Hans Calén, Roger Ruber, Kjell Fransson, I. Koch, M. Bashkanov, Marek Jacewicz, C. Pauly, Y. Petukhov, J. Zabierowski, D. Bogoslowsky, P. Thörngren-Engblom, Pawel Marciniewski, V. Tikhomirov, and O. Khakimova

Subjects
Physics, Nuclear physics, Nuclear and High Energy Physics, Particle physics, Fusion, Pi, Astronomy and Astrophysics, Limiting case (mathematics), Atomic and Molecular Physics, and Optics, Excitation
Abstract

The π0π0 production in pp -collisions has been investigated in exclusive and kinematically complete measurements from threshold up to Tp = 1.4 GeV . For incident energies Tp > 1 GeV , i.e. in the region beyond the Roper excitation, the ΔΔ excitation process takes over. The data are well explained by the t-channel ΔΔ process dominated by pion exchange. There is no low-mass enhancement (ABC effect) in the π0π0-invariant mass distribution beyond that given by the conventional t-channel ΔΔ process. This is also true for the limiting case, where the protons are in the quasi-bound 2 He state.

Published
2011
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32. The WASA detector at CELSIUS

Author

R. Bilger, M. Blom, D. Bogoslawsky, A. Bondar, W. Brodowski, H. Calen, I. Chuvilo, H. Clement, V. Dunin, J. Dyring, C. Ekström, K. Fransson, C-J. Friden, L. Gustafsson, S. Häggström, B. Höistad, M. Jacewicz, J. Johanson, A. Johansson, T. Johansson, A. Khoukaz, K. Kilian, N. Kimura, I. Koch, G. Kolachev, M. Komogorov, S. Kullander, A. Kupsc, L. Kurdadze, A. Kuzmin, A. Kuznetsov, P. Marciniewski, A. Martemyanov, B. Martemyanov, B. Morosov, A. Mörtsell, A. Nawrot, W. Oelert, S. Oreshkin, Y. Petukhov, A. Povtorejko, K. Przestrzelska, J. Pätzold, D. Reistad, R.J.M.Y. Ruber, V. Sandukovsky, U. Schuberth, T. Sefzick, V. Sidorov, B. Shwartz, V. Sopov, J. Stepaniak, A. Sukhanov, P. Sundberg, V. Tchernychev, V. Tikhomirov, A. Turowiecki, G. Wagner, Z. Wilhelmi, A. Yamamoto, H. Yamaoka, J. Zabierowski, A. Zernov, and J. Zlomanczuk

Subjects
Physics, Nuclear and High Energy Physics, Spectrometer, Electromagnet, business.industry, Detector, Superconducting magnet, Astrophysics, Particle identification, Particle detector, law.invention, Optics, law, Electrical equipment, Measuring instrument, business
Published
2000
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33. Higher partial waves in pp→ppη near threshold

Author

H. Calén, J. Dyring, G. Fäldt, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, J. Johanson, A. Johansson, T. Johansson, S. Kullander, A. Mörtsell, R. Ruber, J. Złomańczuk, C. Ekström, K. Kilian, W. Oelert, T. Sefzick, R. Bilger, W. Brodowski, H. Clement, G.J. Wagner, A. Bondar, A. Kuzmin, B. Shwartz, V. Sidorov, A. Sukhanov, V. Dunin, B. Morosov, A. Povtorejko, A. Zernov, A. Kupsc, P. Marciniewski, J. Stepaniak, J. Zabierowski, A. Turowiecki, Z. Wilhelmi, and C. Wilkin

Subjects
Physics, Nuclear and High Energy Physics, Energy distribution, Meson, Nuclear Theory, Eta meson, Nuclear physics, Near threshold, Phase space, High Energy Physics::Experiment, Angular anisotropy, Nuclear Experiment, Anisotropy, Sign (mathematics)
Abstract

Exclusive measurements of the production of eta mesons in the p+p->p+p+eta reaction have been carried out at excess energies of 16 and 37 MeV above threshold. The deviations from phase space are dominated by the proton-proton final state interaction and this influences particularly the energy distribution of the eta meson. However, evidence is also presented at the higher energy for the existence of an anisotropy in the angular distributions of the eta meson and also of the final proton-proton pair, probably to be associated with D-waves in this system interfering with the dominant S-wave term. The sign of the eta angular anisotropy suggests that rho-exchange is important for this reaction.

Published
1999
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34. Recent results from the CELSIUS/WASA collaboration on meson production in proton-hydrogen collisions

Author

R. Bilger, A. Bondar, W. Brodowski, H. Calen, H. Clement, J. Dyring, C. Ekström, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, J. Johanson, A. Johansson, T. Johansson, K. Kilian, S. Kullander, A. Kupsc, A. Kuzmin, P. Marciniewski, B. Morosov, A. Mörtsell, W. Oelert, A. Povtorejko, R.J.M.Y. Ruber, U. Schuberth, T. Sefzick, V. Sidorov, B. Shwartz, V. Sopov, J. Stepaniak, A. Sukhanov, V. Tchernychev, A. Turowiecki, G. Wagner, Z. Wilhelmi, J. Zabierowski, A. Zernov, and J. Zlomanczuk

Subjects
Physics, Nuclear reaction, Nuclear and High Energy Physics, Particle physics, Proton, Meson, Nuclear Theory, Hadron, Threshold energy, Nuclear physics, Pion, Deuterium, Physics::Accelerator Physics, Center of mass, Nuclear Experiment
Abstract

Different π and η meson production channels in proton-proton and proton-deuteron collisions have been studied at the CELSIUS storage ring using an internal cluster-jet target setup [1]. During the last years more emphasis has been put on ππ and all but one of the possible channels in proton-proton collisions have been studied. Recently also the quasi-free p+nd+η reaction cross section has been measured at threshold using 1295 MeV protons and target deuterium. Excess energies from threshold to 10 MeV in the center of mass of the final dη system were covered. Approaching the threshold the cross section is enhanced compared to phase-space expectations. This behaviour is typical for a strong final-state interaction.

Published
1999
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35. Measurement of the quasifreepn→pnηreaction

Author

H. Calén, J. Dyring, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, A. Johansson, T. Johansson, S. Kullander, A. Mörtsell, R. Ruber, U. Schuberth, J. Złomańczuk, C. Ekström, K. Kilian, W. Oelert, T. Sefzick, R. Bilger, W. Brodowski, H. Clement, G. J. Wagner, A. Bondar, A. Kuzmin, B. Shwartz, V. Sidorov, A. Sukhanov, A. Kupść, P. Marciniewski, J. Stepaniak, V. Dunin, B. Morosov, A. Povtorejko, A. Zernov, J. Zabierowski, A. Turowiecki, and Z. Wilhelmi

Subjects
Physics, Excitation function, Momentum, Nuclear and High Energy Physics, Range (particle radiation), Cover (topology), Deuterium, Nuclear Theory, Neutron, Atomic physics, Nuclear Experiment, Energy (signal processing), Fermi Gamma-ray Space Telescope
Abstract

The first measurement of the cross section of the quasifree $p\stackrel{\ensuremath{\rightarrow}}{n}\mathrm{pn}\ensuremath{\eta}$ reaction has been carried out at the CELSIUS storage ring using a deuterium internal cluster jet target. The energy dependence of the cross section is extracted using a fixed incident proton energy of ${T}_{p}=1350 \mathrm{MeV}$ and exploiting the Fermi momentum of the struck neutron. The data cover a range of center-of-mass excess energies from 16 to 109 MeV. The shape of the excitation function is broadly similar to that of the $p\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{pp}\ensuremath{\eta}$ reaction, though with a cross section about a factor of 6.5 larger.

Published
1998
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36. Threshold Structure of the Quasifreep+n→d+ηReaction

Author

H. Calén, J. Dyring, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, J. Johanson, A. Johansson, T. Johansson, A. Khoukaz, S. Kullander, R. J. M. Y. Ruber, J. Złomańczuk, B. Morosov, A. Povtorejko, A. Sukhanov, A. Zernov, A. Kupść, P. Marciniewski, J. Stepaniak, R. Bilger, W. Brodowski, H. Clement, G. J. Wagner, C. Ekström, J. Zabierowski, A. Bondar, A. Kuzmin, B. Shwartz, V. Sidorov, A. Turowiecki, Z. Wilhelmi, K. Kilian, W. Oelert, T. Sefzick, V. Sopov, and V. Tchernychev

Subjects
Physics, Cross section (physics), Deuterium, Proton, Nuclear Theory, Physics::Accelerator Physics, General Physics and Astronomy, Atomic physics, Nuclear Experiment, Storage ring
Abstract

The quasifree p + n --> d + eta reaction cross section has been measured at the threshold using 1295 MeV protons in the CELSIUS storage ring and an internal cluster-jet deuterium target. The kinematics is chosen such that the target proton can be assumed

Published
1998
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37. CELSIUS as an η factory

Author

A. Martemyanov, G. J. Wagner, V. Tikhomirov, Hans Calén, M. Gornov, H. Clement, J. Moehn, B. Morosov, Kjell Fransson, Akira Yamamoto, A. Nawrot, W. Oelert, G. M. Kolachev, R. Bilger, J. Zabierowski, A.E. Bondar, A. Turowiecki, Roger Ruber, S. Dahlgren, W. Brodowski, B. Shwartz, J. Stepaniak, Pawel Marciniewski, Yu. B. Gurov, S. Sandukovsky, A. Zernov, V. Tchernyshev, Z. Pawlowski, A. A. Kuznetsov, Leif Gustafsson, Andrzej Kupsc, D. Reistad, A. Povtorejko, T. Johansson, Y. Yuasa, K. Kilian, M. Komogorov, Bo Höistad, L. Komogorova, V.A. Sidorov, T. Purlatz, R. Shafigullin, V. B. Dunin, Hiromi Hirabayashi, I. Chuvilo, A. Jansson, M. Blom, Z. Wilhelmi, B. Chernyshev, V. Sopov, S. Häggström, C.-J. Fridén, S. Kullander, A.I. Sukhanov, H. Ikegami, Jozef Zlomanczuk, Y. Mizuno, A. Kuzmin, D. Bogoslawsky, Arne Johansson, A. Yamaoka, and C. Ekström

Subjects
Nuclear physics, Physics, Nuclear and High Energy Physics, Particle physics, Meson, Degree Celsius, Factory (object-oriented programming), High Energy Physics::Experiment, Nuclear Experiment, Ring (chemistry), Physics::Atmospheric and Oceanic Physics, Storage ring
Abstract

The WASA project at the CELSIUS storage ring is being prepared for high-luminosity experiments to study rare decays of light mesons, in particular the η meson. The CELSIUS ring together with the newly developed pellet target will serve as an efficient η factory.

Published
1997
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38. Measurement of the Quasifreep+n→d+ηReaction near Threshold

Author

H. Calén, J. Dyring, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, A. Johansson, T. Johansson, S. Kullander, A. Mörtsell, R. J. M. Y. Ruber, U. Schuberth, J. Zlomanczuk, C. Ekström, K. Kilian, W. Oelert, V. Renken, T. Sefzick, A. Bondar, A. Kuzmin, B. Shwartz, V. Sidorov, A. Sukhanov, A. Kupsc, P. Marciniewski, J. Stepaniak, V. Dunin, B. Morosov, A. Povtorejko, A. Zernov, J. Zabierowski, and Z. Wilhelmi

Subjects
Nuclear reaction, Physics, Meson, Nuclear Theory, Hadron, General Physics and Astronomy, The Svedberg Laboratory, Momentum, Nuclear physics, Deuterium, Neutron, Center of mass, Atomic physics, Nuclear Experiment
Abstract

The quasifree p+n{r_arrow}d+{eta} reaction cross section has been measured in the near-threshold region using deuterium from an internal cluster-jet target and 1350 MeV protons in the CELSIUS storage ring of the The Svedberg Laboratory, Uppsala. The energy dependence of the cross section is extracted by exploiting the Fermi momentum of the target neutron and reconstructing the kinematics on an event-by-event basis. The data cover center of mass excess energies from 16 to 113 MeV. {copyright} {ital 1997} {ital The American Physical Society}

Published
1997
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39. Detector setup for a storage ring with an internal target

Author

H. Calén, S. Carius, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, A. Johansson, T. Johansson, S. Kullander, A. Mörtsell, J. Möhn, R. Ruber, U. Schuberth, J. Złomańczuk, C. Ekström, C.-J. Fridén, D. Reistad, K. Kilian, W. Oelert, V. Renken, T. Sefzick, M. Waters, A. Bondar, G. Kolachev, A. Kuzmin, T. Purlatz, B. Shwartz, V. Sidorov, A. Sukhanov, A. Kupść, P. Marciniewski, A. Nawrot, J. Stepaniak, D. Bogoslawsky, V. Dunin, A. Kuznetsov, B. Morosov, A. Povtorejko, S. Sandukovsky, A. Zernov, J. Zabierowski, A. Turowiecki, Z. Wilhelmi, Z. Pawlowski, R. Bilger, W. Brodowski, H. Clement, G. Kurz, G.J. Wagner, A. Martemyanov, V. Sopov, V. Tchernyshev, E. David, M. Price, and C. Rivoiron

Subjects
Physics, Nuclear and High Energy Physics, Range (particle radiation), Photon, Physics::Instrumentation and Detectors, Nuclear Theory, Detector, Scintillator, Particle detector, Charged particle, Scintillation counter, Atomic physics, Nuclear Experiment, Instrumentation, Storage ring
Abstract

A detector setup for the cooler storage ring CELSIUS is described. The setup detects particles produced in interactions between the internal beam and a cluster-jet target. Particles emitted in the forward direction are measured by means of arrays of plastic scintillators and proportional counters. Particles, particularly photons, emitted more isotropically are measured by means of two calorimeters containing CsI(Na) crystals. The performance of the setup is given for neutral meson production in proton-proton and proton-deuteron interactions in the energy range 290–1360 MeV.

Published
1996
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40. The pp → ppη reaction near the kinematical threshold

Author

H. Calén, S. Carius, K. Fransson, L. Gustafsson, S. Häggström, B. Höistad, A. Johansson, T. Johansson, S. Kullander, J. Moehn, A. Mörtsell, R. Ruber, U. Schuberth, J. Zlomanczuk, C. Ekström, K. Kilian, W. Oelert, M. Waters, A. Bondar, A. Kuzmin, B. Shwartz, V. Sidorov, A. Kupsc, J. Stepaniak, B. Morosov, A. Povtorejko, A. Sukhanov, J. Zabierowski, and Z. Wilhelmi

Subjects
Nuclear and High Energy Physics
Published
1996
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41. The pp → ppπ0 reaction near the kinematical threshold

Author

Staffan Carius, C. Ekström, Arne Johansson, A.E. Bondar, A. Kupść, M. Waters, K. Kilian, Leif Gustafsson, Z. Wilhelmi, D. Reistad, S. Häggström, B. Morosov, Bo Höistad, Roger Ruber, A. Kuzmin, B. Shwartz, J. Stepaniak, Tord Johansson, Hans Calén, U. Schuberth, V. Tchernyshev, S. Sandukovsky, J. Zabierowski, A. Povtorejko, A. Mörtsell, Kjell Fransson, S. Kullander, J. Zlomanczuk, A. Sukhanov, and W. Oelert

Subjects
Physics, Nuclear and High Energy Physics, Jet (fluid), Photon, Spectrometer, Nuclear Theory, Dalitz plot, Scintillator, Nuclear physics, Invariant mass, Atomic physics, Nuclear Experiment, Storage ring, Event reconstruction
Abstract

The pp → ppη reaction has been measured at six energies close to threshold, from 1258 MeV to 1352 MeV, using an internal cluster gas jet target in the CELSIUS storage ring. The η is detected through its decay photons, in an array of CsI detectors, and the forward-going protons are detected in a plastic scintillator spectrometer. A complete event reconstruction is obtained at the higher energies in the measured interval. The new data, together with earlier data, give an accurate determination of the energy dependence close to threshold. The influence of the η-proton FSI is seen in the total cross section data as well as in a Dalitz plot of the η-p invariant mass distributions.

Published
1995
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42. Production of the ω meson in thepd→He3ωreaction at 1450 MeV and 1360 MeV

Author

Jozef Zlomanczuk, M. Bashkanov, M. Berłowski, R. Shafigullin, Magnus Wolke, P Khemchandani, J Wagner, C. Ekström, Leif Gustafsson, T. Skorodko, Tikhomirov, Sopov, Wolfgang Scobel, Karin Schönning, A. Turowiecki, F. Kren, B. Höistad, Y. Petukhov, H. Clement, G. Ivanov, D. Bogoslawsky, P. Thörngren Engblom, Andrzej Kupsc, Hans Calén, A. Povtorejko, C. Pauly, R. J. M. Y. Ruber, I. Zartova, B. Morosov, T. Johansson, H. Petrén, B. Shwartz, Colin Wilkin, J. Stepaniak, K. Lindberg, W. Oelert, S. Keleta, E. Jiganov, L. Geren, S. Kullander, Chr. Bargholtz, A. Kuzmin, J. Zabierowski, Pawel Marciniewski, P.-E. Tegnér, K. Fransson, L. Demiroers, Marek Jacewicz, and O. Khakimova

Subjects
Physics, Scattering cross-section, Nuclear reaction, Nuclear and High Energy Physics, Meson, 010308 nuclear & particles physics, Nuclear Theory, 01 natural sciences, Omega, Nuclear physics, Angular distribution, Pion, Helium-3, 0103 physical sciences, Physics::Accelerator Physics, Nuclear Experiment, 010306 general physics
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 w ...

Published
2009
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43. 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

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

Author

Jozef Zlomanczuk, H. Petrén, J. Zabierowski, Marek Jacewicz, E. Doroshkevich, S. Keleta, A. Kupść, C. Ekström, C. Pauly, Wolfgang Scobel, E. Jiganov, H. Clement, F. Kren, T. Johansson, Karin Schönning, S. Kullander, Bo Höistad, R. J. M. Y. Ruber, Akira Yamamoto, R. Meier, B. Morosov, O. Khakimova, L. Demiroers, A. Povtorejko, D. Bogoslawsky, B. Shwartz, J. Stepaniak, T. Skorodko, M. Bashkanov, Leif Gustafsson, Pawel Marciniewski, V. Tikhomirov, Hans Calén, I. Koch, K. Fransson, P. Thörngren-Engblom, G. J. Wagner, G. Ivanov, Y. Petukhov, and Magnus Wolke

Subjects
Physics, Scattering cross-section, Nuclear and High Energy Physics, Particle physics, Proton, FOS: Physical sciences, Resonance (particle physics), Decomposition, Nuclear physics, Pion, Isospin, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment, Excitation
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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45. Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements

Author

M. Bashkanov, Y. Petukhov, E. Doroshkevich, Sven Kullander, Henrik Pettersson, K. Lindberg, L. Geren, A. Povtorejko, Tord Johansson, M. Berłowski, Marek Jacewicz, David Duniec, H. Clement, O. Khakimova, C. Pauly, Karin Schönning, A. Pricking, A. Turowiecki, G. Ivanov, Leif Gustafsson, P.-E. Tegnér, Bo Höistad, T. Skorodko, E. Jiganov, C. Bargholtz, Andrzej Kupsc, Jozef Zlomanczuk, Pawel Marciniewski, Curt Ekstrom, V. Sopov, Wolfgang Scobel, L. Demiroers, F. Kren, M. Wolke, Hans Calén, R. Meier, V. Tikhomirov, D. Bogoslawsky, Kjell Fransson, I. Zartova, G. J. Wagner, J. Zabierowski, P. Thörngren-Engblom, S. Keleta, B. Morosov, B. Shwartz, J. Stepaniak, Roger Ruber, and I. Koch

Subjects
Particle physics, two-pion [mass spectrum], Dalitz plot, General Physics and Astronomy, Hexaquark, FOS: Physical sciences, Nuclear physics, ddc:550, Intermediate state, Invariant mass, angular distribution, +deuteron+2pi0%22">p n --> deuteron 2pi0, Nuclear Experiment (nucl-ex), Nuclear Experiment, Physics, Fusion, experimental results [magnetic spectrometer], 1.35 GeV-kin [1.03], Spectrum (functional analysis), mass enhancement, Uppsala CELSIUS Stor, Pair production, pair production [pi], isoscalar [dibaryon], Mass spectrum, fusion [p n], energy dependence [cross section], (2Delta(1232)) [intermediate state]
Abstract

The ABC effect-a puzzling low-mass enhancement in the pi pi invariant mass spectrum, first observed by Abashian, Booth, and Crowe-is well known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on the first exclusive and kinematically complete measurements of the most basic double-pionic fusion reaction pn -> d pi(0)pi(0) at beam energies of 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 resonancelike 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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46. Measurement of the slope parameter for theη→3π0decay in thepp→ppηreaction

Author

Hans Calén, V. Tikhomirov, J. Zabierowski, G. J. Wagner, R. J. M. Y. Ruber, Jozef Zlomanczuk, E. Jiganov, Magnus Wolke, T. Skorodko, A. A. Kuznetsov, P. Thörngren Engblom, Marek Jacewicz, H. Clement, Wolfgang Scobel, R. Meier, C. Pauly, Ulrich Wiedner, V. Tchernyshev, L. Demirörs, D. Bogoslawsky, H. Pettersson, Karin Schönning, F. Capellaro, S. Kullander, A. Turowiecki, A. Povtorejko, C. Ekström, W. Oelert, M. Bashkanov, Leif Gustafsson, A. Kupść, T. Johansson, V. Sopov, B. Höistad, Y. Petukhov, G. Ivanov, I. Koch, S. Keleta, Pawel Marciniewski, Akira Yamamoto, K. Fransson, B. Morosov, B. Shwartz, and J. Stepaniak

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Meson, Dalitz plot, Kinetic energy, Measure (mathematics), Particle identification, Nuclear physics, Particle decay, Distribution (mathematics), High Energy Physics::Experiment, Nuclear Experiment, Beam (structure)
Abstract

The CELSIUS-WASA setup is used to measure the 3{pi}{sup 0} decay of {eta} mesons produced in pp interactions with beam kinetic energies of 1.36 and 1.45 GeV. The efficiency-corrected Dalitz plot and density distributions for this decay are shown, together with a fit of the quadratic slope parameter {alpha} yielding {alpha}=-0.026{+-}0.010(stat){+-}0.010(syst). This value is compared to recent experimental results and theoretical predictions.

Published
2007
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47. Measurement of eta meson decays into lepton-antilepton pairs

Author

WASA Collaboration, Ber��owski, M., Bargholtz, Chr., Bashkanov, M., Bogoslawsky, D., Bondar, A., Cal��n, H., Cappellaro, F., Clement, H., Demir��rs, L., Ekstr��m, C., Fransson, K., Ger��n, L., Gustafsson, L., H��istad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Koch, I., Kullander, S., Kup����, A., Kuzmin, A., Kuznetsov, A., Laukhin, I. V., Lindberg, K., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Sch��nning, K., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tegn��r, P. -E., Engblom, P. Th��rngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Zartova, I., and Z��oma��czuk, J.

Subjects
Nuclear and High Energy Physics, Particle physics, Meson, Nuclear Theory, decay modes [eta], Dalitz plot, FOS: Physical sciences, Electron, Particle identification, exclusive reaction [p deuteron], High Energy Physics - Experiment, Nuclear physics, Particle decay, High Energy Physics - Experiment (hep-ex), pair production [lepton], +helium-3+eta%22">p deuteron --> helium-3 eta, +2lepton%2B+2lepton%22">eta --> 2lepton+ 2lepton, ddc:530, +2positron+2electron%22">eta --> 2positron 2electron, semileptonic decay [eta], Nuclear Experiment, 0.893 GeV, +pi%2B+pi-+muon%2B+muon%22">eta --> pi+ pi- muon+ muon, branching ratio [eta], Physics, hadroproduction [eta], experimental results [magnetic spectrometer], leptonic decay [eta], Branching fraction, High Energy Physics::Phenomenology, Eta meson, +positron+electron%22">eta --> positron electron, Uppsala CELSIUS Stor, +2muon%2B+2muon%22">eta --> 2muon+ 2muon, High Energy Physics::Experiment, +positron+electron+photon%22">eta --> positron electron photon, upper limit, Lepton, experimental results
Abstract

A search for rare lepton decays of the eta meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay eta->e+e-e+e- events are reported with a background of 1.3+/-0.2 events. This allows to set an upper limit to the branching ratio of 9.7E-5 (90% CL). The branching ratio for the decay eta->e+e-gamma is determined to (7.8+/-0.5 stat+/-0.8 syst)E-3. An upper limit (90% CL) for the branching ratio for the eta->e+e- decay is 2.7E-5 and a limit for the sum of the eta->mu+mu-mu+mu- and eta->pi+pi-mu+mu- decays is 3.6E-4., 9 pages, 10 Postscript figures, uses revtex4.sty, revised version after referee comments; conclusions unchanged

Published
2007
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48. 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

H. Clement, M. Bashkanov, C. Bargholtz, D. Bogoslawsky, H. Calen, F. Cappellaro, L. Demiroers, E. Doroshkevich, D. Duniec, C. Ekström, K. Franssen, L. Geren, L. Gustafsson, B. Höistad, G. Ivanov, M. Jacewicz, E. Jiganov, T. Johansson, M. Kaskulov, O. Khakimova, S. Keleta, I. Koch, F. Kren, S. Kullander, A. Kupść, A. Kuznetsov, K. Lindberg, P. Marciniewski, R. Meier, B. Morosov, C. Pauly, H. Petterson, Y. Petukhov, A. Povtorejko, A. Pricking, K. Schönning, W. Scobel, B. Shwartz, T. Skorodko, V. Sopov, J. Stepeniak, P.-E. Tegner, P. Thörngren-Engblom, V. Tikhomirov, G.J. Wagner, M. Wolke, A. Yamamoto, J. Zabierowski, I. Zartova, and J. Złomanczuk

Subjects
Physics, Nuclear and High Energy Physics, Isoscalar, Nuclear Theory, Resonance, FOS: Physical sciences, Context (language use), Nuclear physics, Pion, Nuclear fusion, Invariant mass, Production (computer science), Nuclear Experiment (nucl-ex), Nucleon, 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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49. Measurement of the eta->pi+pi-e+e- decay branching ratio

Author

WASA Collaboration, Bargholtz, Chr., Bashkanov, M., Bogoslawsky, D., Cal��n, H., Capellaro, F., Clement, H., Demir��rs, L., Ekstr��m, C., Fransson, K., Ger��n, L., Gustafsson, L., H��istad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Keleta, S., Koch, I., Kullander, S., Kupsc, A., Kuznetsov, A., Laukhin, I. V., Lindberg, K., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pauly, C., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Sch��nning, K., Scobel, W., Shafigullin, R., Shwartz, B., Skorodko, T., Sopov, V., Stepaniak, J., Tchernyshev, V., Tegn��r, P. -E., Engblom, P. Th��rngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wolke, M., Yamamoto, A., Zabierowski, J., Zartova, I., and Z��oma��czuk, J.

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment, Astrophysics::Galaxy Astrophysics
Abstract

The reaction pd->3He eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta->pi+pi-e+e- is measured to be (4.3+/-1.3+/-0.4)x10^-4., 10 pages,6 figures revised version

Published
2006
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50. The pp -> pp pi pi pi reaction channels in the threshold region

Author

WASA Collaboration, Pauly, C., Jacewicz, M., Koch, I., Bashkanov, M., Bogoslawsky, D., Cal��n, H., Capellaro, F., Clement, H., Demir��rs, L., Ekstr��m, C., Fransson, K., Gustafsson, L., H��istad, B., Ivanov, G., Jiganov, E., Johansson, T., Keleta, S., Kullander, S., Kup����, A., Kuznetsov, A., Marciniewski, P., Meier, R., Morosov, B., Oelert, W., Pettersson, H., Petukhov, Y., Povtorejko, A., Ruber, R. J. M. Y., Scobel, W., Sch��nning, K., Skorodko, T., Shwartz, B., Sopov, V., Stepaniak, J., Tchernyshev, V., Engblom, P. Th��rngren, Tikhomirov, V., Turowiecki, A., Wagner, G. J., Wiedner, U., Wolke, M., Yamamoto, A., Zabierowski, J., and Z��oma��czuk, J.

Subjects
FOS: Physical sciences, Nuclear Experiment (nucl-ex)
Abstract

The cross section for prompt neutral and charged three pion production in pp interactions was measured at excess energies in the range 160 - 217 MeV. That comprises the first measurement of the pp->pp pi0pi0pi0 reaction and the comparison with the pp->pp pi+pi-pi0 reaction, in a very direct way. The experiment was performed above the eta meson production threshold and the cross section normalization was obtained from a concurrent measurement of the reaction pp->pp eta with the eta decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio sigma(pp->pp pi+pi-pi0)/sigma(pp->pp pi0\pi0\pi0) is compared to predictions of dominance of different isobars in the intermediate state., 12 pages, 4 figures New discussion on the pp->pp3pi reaction mechanism

Published
2006
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