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48 results on '"Khakimova, O"'

1. 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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2. 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., Thörngren Engblom, P., 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.

Published
2008
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3. 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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4. Production of $ \rightarrow$ 3HeX reaction at 1360 and 1450 MeV

Author

Schönning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, 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., Kupsc, 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., Wolke, M., Zabierowski, J., Zartova, I., and Złomanczuk, J.

Published
2010
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5. 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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9. Exclusive measurement of the eta -> pi(+) pi(-) gamma decay

Author

ADLARSON, P, ADOLPH, C, AUGUSTYNIAK, W, BARDAN, W, BASHKANOV, M, BEDNARSKI, T, BERGMANN, FS, BERLOWSKI, M, BHATT, H, BRINKMANN, KT, BUSCHER, M, CALEN, H, CLEMENT, H, CODERRE, D, CZERWINSKI, E, DOROSHKEVICH, E, ENGELS, R, ERVEN, W, EYRICH, W, FEDORETS, P, FOHL, K, FRANSSON, K, GOLDENBAUM, F, GOSLAWSKI, P, GRIGORYEV, K, GULLSTROM, CO, HANHART, C, HEIJKENSKJOLD, L, HEIMLICH, J, HEJNY, V, HINTERBERGER, F, HODANA, M, HOISTAD, B, JACEWICZ, M, JANY, A, JANY, BR, JARCZYK, L, JOHANSSON, T, KAMYS, B, KEMMERLING, G, KHAKIMOVA, O, KHOUKAZ, A, KISTRYN, S, KLAJA, J, KLEINES, H, KLOS, B, KREN, F, KRZEMIEN, W, KULESSA, P, KUPSC, A, LALWANI, K, LEUPOLD, S, LORENTZ, B, MAGIERA, A, MAIER, R, MARIANSKI, B, MARCINIEWSKI, P, MEISSNER, UG, MIKIRTYCHIANTS, M, MORSCH, HP, MOSKAL, P, NANDI, BK, NIEDZWIECKI, S, OHM, H, PASSFELD, A, PAULY, C, DEL RIO, EP, PETRI, T, PETUKHOV, Y, PISKUNOV, N, PLUCINSKI, P, PODKOPAL, P, POVTOREYKO, A, PRASUHN, D, PRICKING, A, PYSZ, K, PYSZNIAK, A, RAUSMANN, T, REDMER, CF, 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, STROHER, H, SZCZUREK, A, TASCHNER, A, TERSCHLUSEN, C, TOLBA, T, TRZCINSKI, A, VARMA, R, VLASOV, P, WAGNER, GJ, WEGLORZ, W, WINNEMOLLER, A, WIRZBA, A, WOLKE, M, WRONSKA, A, WUSTNER, P, WURM, P, YUAN, X, YUREV, L, ZABIEROWSKI, J, ZHENG, C, ZIELINSKI, MJ, ZIPPER, W, ZLOMANCZUK, J, and ZUPRANSKI, P

Subjects
Exclusive Measurement, Eta Meson, Box Anomaly
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 -> He-3 X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13 960 +/- 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 -> 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. (C) 2011 Elsevier B.V All rights reserved.

Published
2012
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10. 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
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11. $\pi ^{0} \pi ^{0}$ production in proton–proton collisions at $T_{p} = 1.4$ GeV

Author

Adlarson, P., Adolph, C., Augustyniak, W., 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., Heijkenskjöld, L., Heimlich, J., Hejny, V., Hinterberger, F., Hodana, Małgorzata, Höistad, B., Jacewicz, M., Janusz, Michał, 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., Lorentz, B., Magiera, Andrzej, Maier, R., Mariański, B., Marciniewski, P., Mikirtychiants, M., Morsch, H.-P., Moskal, Paweł, Nandi, B. K., Niedźwiecki, Szymon, Ohm, H., Passfeld, A., Pauly, C., Perez del Rio, Elena, Petukhov, Y., Piskunov, N., Pluciński, P., Podkopał, Paweł, Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., 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., Skorodko, T., Skurzok, Magdalena, Smyrski, Jerzy, 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, Aleksandra, Wüstner, P., Wurm, P., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, Marcin, Zipper, W., Złomańczuk, J., and Żuprański, P.

Published
2012

12. pi(0)pi(0) Production in proton-proton collisions at T-p=1.4 GeV The WASA-at-COSY Collaboration

Author

ADLARSON, P, ADOLPH, C, AUGUSTYNIAK, W, BASHKANOV, M, BEDNARSKI, T, BERGMANN, FS, BERLOWSKI, M, BHATT, H, BRINKMANN, KT, BUSCHER, M, CALEN, H, CLEMENT, H, CODERRE, D, CZERWINSKI, E, DOROSHKEVICH, E, ENGELS, R, ERVEN, W, EYRICH, W, FEDORETS, P, FOHL, K, FRANSSON, K, GOLDENBAUM, F, GOSLAWSKI, P, GRIGORYEV, K, GULLSTROM, CO, HEIJKENSKJOLD, L, HEIMLICH, J, HEJNY, V, HINTERBERGER, F, HODANA, M, HOISTAD, B, JACEWICZ, M, JANUSZ, M, JANY, A, JANY, BR, JARCZYK, L, JOHANSSON, T, KAMYS, B, KEMMERLING, G, KHAKIMOVA, O, KHOUKAZ, A, KISTRYN, S, KLAJA, J, KLEINES, H, KLOS, B, KREN, F, KRZEMIEN, W, KULESSA, P, KUPSC, A, LALWANI, K, LORENTZ, B, MAGIERA, A, MAIER, R, MARIANSKI, B, MARCINIEWSKI, P, MIKIRTYCHIANTS, M, MORSCH, HP, MOSKAL, P, NANDI, BK, NIEDZWIECKI, S, OHM, H, PASSFELD, A, PAULY, C, DEL RIO, EP, PETUKHOV, Y, PISKUNOV, N, PLUCINSKI, P, PODKOPAL, P, POVTOREYKO, A, PRASUHN, D, PRICKING, A, PYSZ, K, RAUSMANN, T, REDMER, CF, 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, STROHER, H, SZCZUREK, A, TASCHNER, A, TOLBA, T, TRZCINSKI, A, VARMA, R, VLASOV, P, WAGNER, GJ, WEGLORZ, W, WIEDNER, U, WINNEMOLLER, A, WOLKE, M, WRONSKA, A, WUSTNER, P, WURM, P, YUAN, X, YUREV, L, ZABIEROWSKI, J, ZHENG, C, ZIELINSKI, MJ, ZIPPER, W, ZLOMANCZUK, J, and ZUPRANSKI, P

Subjects
Roper Resonance, Pion Production, Pp, Cross-Sections, 2-Pion Production, Excitation, Model
Abstract

The reaction pp -> pp pi(0)pi(0) 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)) mu b. 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 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. (C) 2011 Elsevier B.V. All rights reserved.

Published
2012

13. 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

14. 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
High Energy Physics::Experiment, 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

15. 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
FOS: Physical sciences, Nuclear Experiment (nucl-ex), 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

16. 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
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17. ΔΔ excitation in proton–proton induced ${\pi }^{0}{\pi }^{0}$ production

Author

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

Subjects
ddc:530
Published
2011
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18. 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 Theory, Nuclear Experiment
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

19. 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

20. Exclusive measurements of $pp\to d{\pi }^{+}{\pi }^{0}$: Double-pionic fusion without ABC effect

Author

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

Subjects
ddc:530
Abstract

Exclusive measurements of the reaction pp→dπ+π0pp→dπ+π0 have been carried out at Tp=1.1 GeVTp=1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector π+π0π+π0 channel exhibits no enhancement at low invariant ππ masses, i.e. no ABC effect. Therefore this most basic isovector double-pionic fusion reaction qualifies as an ideal test case for the conventional t-channel ΔΔ excitation process. Indeed, the obtained differential distributions reveal the conventional t-channel ΔΔ mechanism as the appropriate reaction process, which also accounts for the observed energy dependence of the total cross section.

Published
2010
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21. 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
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22. 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 Theory, 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

23. 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
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24. 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
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25. Measurement of the $\eta \rightarrow 3\pi ^{0}$ Dalitz plot distribution with the WASA detector at COSY

Author

Adolph, C., Angelstein, M., Bashkanov, M., Bechstedt, U., Belostotski, S., Berłowski, M., Bhatt, H., Bisplinghoff, J., Bondar, A., Borasoy, B., Büscher, M., Calén, H., Chandwani, K., Clement, H., Czerwiński, Eryk, Czyżykiewicz, Rafał, D'Orsaneo, G., Duniec, D., Ekström, C., Engels, R., Erven, W., Eyrich, W., Fedorets, P., Felden, O., Fransson, K., Gil, Damian, Goldenbaum, F., Grigoryev, K., Heczko, Andrzej, Hanhart, C., Hejny, V., Hinterberger, F., Hodana, M., Höistad, B., Izotov, A., Jacewicz, M., Janusz, Michał, Jany, Benedykt, Jarczyk, Lucjan, Johansson, T., Kamys, Bogusław, Kemmerling, G., Keshelashvili, I., Khakimova, O., Khoukaz, A., Kilian, K., Kimura, N., Kistryn, Stanisław, Klaja, Joanna, Klaja, Paweł, Kleines, H., Klos, B., Kowalczyk, A., Kren, F., Krzemień, Wojciech, Kulessa, P., Kullander, S., Kupść, A., Kuzmin, A., Kyryanchuk, V., Majewski, J., Machner, H., Magiera, Andrzej, Maier, R., Marciniewski, P., Migdał, Wojciech, Meißner, U.-G., Mikirtychiants, M., Miklukho, O., Milke, N., Mittag, M., Moskal, Paweł, Nandi, B. K., Nawrot, A., Nißler, R., Odoyo, M. A., Oelert, W., Ohm, H., Paul, N., Pauly, C., Petukhov, Y., Piskunov, N., Pluciński, P., Podkopał, Paweł, Povtoreyko, A., Prasuhn, D., Pricking, A., Pysz, K., Rachowski, J., Rausmann, T., Redmer, C. F., Ritman, J., Roy, A., Ruber, R. J. M. Y., Rudy, Zbigniew, Salmin, R., Schadmand, S., Schmidt, A., Schneider, H., Schroeder, W., Scobel, W., Sefzick, T., Serdyuk, V., Shah, N., Siemaszko, M., Siudak, R., Skorodko, T., Smoliński, Tytus, Smyrski, Jerzy, Sopov, V., Spölgen, D., Stepaniak, J., Sterzenbach, G., Ströher, H., Szczurek, A., Teufel, A., Tolba, T., Trzciński, A., Ulbrich, K., Varma, R., Vlasov, P., Weglorz, W., Winnemöller, A., Wirzba, A., Wolke, M., Wrońska, Aleksandra, Wüstner, P., Xu, H., Yamamoto, A., Yamaoka, H., Yuan, X., Yurev, L., Zabierowski, J., Zheng, C., Zieliński, Marcin, Zipper, W., Złomańczuk, J., Zwoll, K., and Zychor, I.

Published
2009

26. 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
High Energy Physics::Phenomenology, Nuclear Theory, High Energy Physics::Experiment, 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

27. 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
FOS: Physical sciences, Nuclear Experiment (nucl-ex), 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

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
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29. 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
PIONS -- Scattering, BARYONS, NUCLEAR excitation, MASS spectrometry, NUCLEAR physics
Abstract

The two-pion production in nucleon-nucleon collisions has been studied by exclusive and kinematically complete experiments from threshold up to Tp = 1.36 GeV at CELSIUS-WASA. At near-threshold energies the total and differential distributions for the π+π- and π0π0 channels are dominated by Roper excitation and its decay into Nσs and Δπ channels. At beam energies Tp>1.1 GeV the ΔΔ excitation governs the two-pion production process. In the π+π+ channel evidence is found for the excitation of a higher-lying I =3/2 resonance, favorably the Δ(1600). The isovector fusion processes leading to the deuteron and to quasi-stable 2He, respectively, exhibit no or only a modest ABC-effect, i.e. low-mass enhancement in the ππ-invariant mass spectrum, and can be described by conventional t-channel ΔΔ excitation. On the other hand, the isoscalar fusion process to the deuteron 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 ΔΔ mass. [ABSTRACT FROM AUTHOR]

Published
2010
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30. Production of $ \eta$ and 3 $ \pi$ mesons in the pd $ \rightarrow$3HeX reaction at 1360 and 1450 MeV.

Author

Schönning, K., Bargholtz, Chr., Bashkanov, M., Berlowski, 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., and Kren, F.

Subjects
MESONS, PARTICLES (Nuclear physics), RESONANCE, CIRCLE-squaring, ISOBARIC spin
Abstract

The cross-sections of the pd $ \rightarrow$3He $ \eta$ , pd $ \rightarrow$3He $ \pi^{0}_{}$ $ \pi^{0}_{}$ $ \pi^{0}_{}$ and pd $ \rightarrow$3He $ \pi^{+}_{}$ $ \pi^{-}_{}$ $ \pi^{0}_{}$ reactions have been measured at the beam kinetic energies Tp= 1360 MeV and Tp= 1450 MeV using the CELSIUS/WASA detector setup. At both energies, the differential cross-section $\tfrac{{d\sigma }} {{d\Omega }}$ of the $ \eta$ meson in the pd $ \rightarrow$3He $ \eta$ reaction shows a strong forward-backward asymmetry in the CMS. The ratio between the pd $ \rightarrow$3He $ \pi^{+}_{}$ $ \pi^{-}_{}$ $ \pi^{0}_{}$ and pd $ \rightarrow$3He $ \pi^{0}_{}$ $ \pi^{0}_{}$ $ \pi^{0}_{}$ cross-sections has been analysed in terms of isospin amplitudes. The reconstructed invariant-mass distributions of the $ \pi$ $ \pi$ , 3He $\displaystyle \pi$ and 3He2 $ \pi$ systems provide hints on the role of nucleon resonances in the 3 $ \pi$ production process. [ABSTRACT FROM AUTHOR]

Published
2010
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31. η PRODUCTION IN PROTON-PROTON COLLISIONS AT 72 MeV EXCESS ENERGY.

Author

PETTERSSON, H., BASHKANOV, M., BOGOSLOWSKY, D., CALÉN, H., CLEMENT, H., EKSTRÖM, C., FRANSSON, K., GUSTAFSSON, L., HÖISTAD, B., IVANOV, G., JACEWICZ, M., JIGANOV, E., JOHANSSON, T., KELETA, S., KHAKIMOVA, O., KOCH, I., KREN, F., KULLANDER, S., KUPŚĆ, A., and KUZNETSOV, A.

Subjects
PROTON-proton interactions, MESONS, NUCLEAR excitation, PARTICLES (Nuclear physics), NUCLEAR reactions, NUCLEAR physics
Abstract

The production of η mesons at an excess energy of 72 MeV has been studied in the reaction pp → pp(η)γγ. It is shown that a simple model with Pp final states included reproduces observed differential distributions better than the same model restricted to Ss, Sd and Ds final states. The strong influence of the Pp states could be taken as an indication of ρ dominance within an one boson exchange model for the excitation of N*(1535). [ABSTRACT FROM AUTHOR]

Published
2009

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

Author

SKORODKO, T., BASHKANOV, M., BOGOSLOWSKY, D., CALÉN, H., CLEMENT, H., EKSTRÖM, C., FRANSSON, K., GUSTAFSSON, L., HÖISTAD, B., IVANOV, G., JACEWICZ, M., JIGANOV, E., JOHANSSON, T., KELETA, S., KHAKIMOVA, O., KOCH, I., KREN, F., KULLANDER, S., KUPŚĆ, A., and KUZNETSOV, A.

Subjects
NUCLEAR excitation, ISOBARIC spin, PARTICLES (Nuclear physics), COLLISIONS (Nuclear physics), NUCLEAR reactions, NUCLEAR physics
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. [ABSTRACT FROM AUTHOR]

Published
2009

33. OBSERVATION OF THE ABC EFFECT IN THE FIRST EXCLUSIVE MEASUREMENTS OF pn → dπ0π0.

Author

Khakimova, O., Bashkanov, M., Skorodko, T., Bargholtz, C., Bogoslowsky, D., Calén, H., Cappellaro, F., Clement, H., Ekström, C., Fransson, K., Geren, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Kaskulov, M. M., Keleta, S., and Koch, I.

Subjects
*NUCLEAR reactions, *MASS spectrometry, *NUCLEAR physics, *COLLISIONS (Nuclear physics), *NUCLEAR energy
Abstract

The reaction pn → dπ0π0 constitutes the most fundamental system for the study of the ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of the ππ system in double-pionic fusion to nuclear bound states. The first exclusive measurements of this reaction have now been carried out at CELSIUS-WASA. They exhibit a striking low-mass enhancement in the ππ invariant mass spectrum, prove it to be a σ-channel phenomenon and falsify conventional theoretical models, which predict an associated high-mass enhancement not present in the new exclusive data. In the kinematically complete data sample we observe a ΔΔ excitation, where the interaction between the two Δ obviously plays a crucial role for the generation of the ππ low-mass enhancement. [ABSTRACT FROM AUTHOR]

Published
2007

34. LOW-MASS ππ ENHANCEMENT IN BARYONIC ππ PRODUCTION:: ABC EFFECT REVISED BY EXCLUSIVE MEASUREMENTS.

Author

Bashkanov, M., Khakimova, O., Skorodko, T., Bargholtz, C., Bogoslowsky, D., Calén, H., Cappellaro, F., Clement, H., Ekström, C., Fransson, K., Geren, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Kaskulov, M. M., Keleta, S., and Koch, I.

Subjects
*BARYONS, *NUCLEAR reactions, *FERMIONS, *HADRONS, *HEAVY particles (Nuclear physics), *PIONS
Abstract

The ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge ππ threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a σ-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of πππ rather than of ππ nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two Δ particles created in this process is of crucial importance. [ABSTRACT FROM AUTHOR]

Published
2007

35. OBSERVATION OF THE ABC EFFECT IN THE FIRST EXCLUSIVE MEASUREMENTS OF pn → dπ0π0.

Author

Khakimova, O., Bashkanov, M., Skorodko, T., Bargholtz, C., Bogoslowsky, D., Calén, H., Cappellaro, F., Clement, H., Ekström, C., Fransson, K., Geren, L., Gustafsson, L., Höistad, B., Ivanov, G., Jacewicz, M., Jiganov, E., Johansson, T., Kaskulov, M. M., Keleta, S., and Koch, I.

Subjects
NUCLEAR reactions, MASS spectrometry, NUCLEAR physics, COLLISIONS (Nuclear physics), NUCLEAR energy
Abstract

The reaction pn → dπ0π0 constitutes the most fundamental system for the study of the ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of the ππ system in double-pionic fusion to nuclear bound states. The first exclusive measurements of this reaction have now been carried out at CELSIUS-WASA. They exhibit a striking low-mass enhancement in the ππ invariant mass spectrum, prove it to be a σ-channel phenomenon and falsify conventional theoretical models, which predict an associated high-mass enhancement not present in the new exclusive data. In the kinematically complete data sample we observe a ΔΔ excitation, where the interaction between the two Δ obviously plays a crucial role for the generation of the ππ low-mass enhancement. [ABSTRACT FROM AUTHOR]

Published
2007

36. ππ PRODUCTION IN PROTON-PROTON COLLISIONS.

Author

Skorodko, T., Bashkanov, M., Bogoslowsky, 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., Khakimova, O., and Koch, I.

Subjects
PROTON-proton interactions, PIONS, COLLISIONS (Nuclear physics), CHIRALITY of nuclear particles, SYNCHROTRONS
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. [ABSTRACT FROM AUTHOR]

Published
2007

37. TWO-PION PRODUCTION, ϒϒ LINE AND ASPECTS OF α MESON, BOSE-EINSTEIN CORRELATIONS AND ISOSPIN BREAKING.

Author

Clement, H., Bashkanov, M., Doroshkevich, E., Kaskulov, M., Khakimova, O., Kren, F., Meier, R., Skorodko, T., Wagner, G. J., Bogoslawsky, D., Ivanov, G., Jiganov, E., Kuznetsov, A., Morosow, B., Petukhov, Y., Povtorejko, A., Tikhomirov, V., Calén, H., Ekström, C., and Fransson, K.

Subjects
DETECTORS, ENGINEERING instruments, HYDROGEN, RESONANCE, NEUTRON resonance, ISOBARIC spin
Abstract

The pp → ppx(x = γγ, 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 ppπ°π° channel basically shows similar features, however, develops a peculiar enhancement at small invariant maases Mπ°π° - in resemblance of Bose-Einstein correlations. Alternatively, the enhancement could be also indicative of a (dynamic) isospin breaking due to π°π°ππ rescattering in the σ channel. The latter is favored by the results on pd → ³He x(x = π°π°,π+π-), where the observed π°π° enhancements are still much larger. In the γγ channel a line at Mγγ is observed. The possible nature of this line is discussed. [ABSTRACT FROM AUTHOR]

Published
2005

39. Two-pion production in the ΔΔ region: Is the ABC-effect the result of a resonance in the pn↔ΔΔ system?

Author

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

Subjects
PION production, NUCLEAR fusion, NUCLEAR reactions, MASS spectrometry, COLLISIONS (Nuclear physics), PARTICLES (Nuclear physics)
Abstract

The ABC effect—a puzzling low-mass enhancement in the ππ invariant mass spectrum—is known from inclusive measurements of two-pion production in nuclear fusion reactions. Exclusive measurements conducted at CELSIUS-WASA for the fusion reactions leading to d and 3He in the final state reveal the ABC effect to be of scalar-isoscalar nature and to be associated with the formation of a resonance in the pn↔ΔΔ systems in the intermediate state. The differential distributions for the π0π0 channels can be well described, if a quasi-bound state within the ΔΔ system is assumed, which gives rise to a resonance structure in the total cross section. This ansatz is capable of describing all differential cross sections including the results of previous inclusive measurements on 4He as well as the energy dependence of the total cross sections. [ABSTRACT FROM AUTHOR]

Published
2007
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40. Large σ Channel Low-Mass Enhancement in Exclusively Measured Double Pionic Fusion to 3He.

Author

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

Subjects
PIONS, PARTICLES (Nuclear physics), NUCLEAR counters, DETECTORS, NUCLEAR physics
Abstract

The pd → 3He π0π0 and pd → 3He π+π- reactions have been measured exclusively at CELSIUS using the WASA 4π detector with pellet target system. For the double-pionic fusion to 3He data have been taken at Tp = 0.893 GeV, where the maximum of the socalled ABC effect is expected. A very large low-mass enhancement is observed in the π0π0 invariant mass spectrum Mπ0π0, whereas only a moderate low-mass enhancement is seen in Mπ+π- raising thus the question of isospin invariance in this region. With both channels summed up the data agree well to previous inclusive measurements regarding the low-mass enhancement. However, they do not exhibit the high-mass enhancement seen in the inclusive measurements and predicted by theoretical calculations based on a ΔΔ process, which produces a double-hump structure in the Mππ spectra. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2006
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41. 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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42. THE pp → ppπ0π0 REACTION AND ITS LIMITING CASE, FUSION TO QUASI-BOUND 2He, IN SEARCH OF THE ABC EFFECT.

Author

SKORODKO, T., BASHKANOV, M., BOGOSLOWSKY, D., CALÉN, H., CLEMENT, H., DOROSHKEVICH, E., EKSTRÖM, C., FRANSSON, K., GUSTAFSSON, L., HÖISTAD, B., IVANOV, G., JACEWICZ, M., JIGANOV, E., JOHANSSON, T., KELETA, S., KHAKIMOVA, O., KOCH, I., KREN, F., KULLANDER, S., and KUPŚĆ, A.

Subjects
PROTON-proton interactions, NUCLEAR fusion, HELIUM isotopes, NUCLEAR energy, NUCLEAR excitation, ATOMIC mass
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 2He state. [ABSTRACT FROM AUTHOR]

Published
2011

43. THE pp → dπ+π0 REACTION — A CASE OF ΔΔ EXCITATION WITHOUT ABC-EFFECT.

Author

KREN, F., BASHKANOV, M., BOGOSLOWSKY, D., CALÉN, H., CLEMENT, H., EKSTRÖM, C., FRANSSON, K., GUSTAFSSON, L., HÖISTAD, B., IVANOV, G., JACEWICZ, M., JIGANOV, E., JOHANSSON, T., KELETA, S., KHAKIMOVA, O., KOCH, I., KULLANDER, S., KUPŚĆ, A., KUZNETSOV, A., and MARCINIEWSKI, P.

Subjects
NUCLEAR excitation, NUCLEAR fusion, RADIOACTIVE decay, CONTROLLED fusion, NUCLEAR reactions, NUCLEAR physics
Abstract

The ABC effect, a low-mass enhancement in the invariant ππ mass, is observed in double-pionic fusion reactions leading to a bound nuclear system in the final state. From previous measurements there have been indications that this phenomenon is resctricted to the σ channel of the ππ system. With exclusive measurements of the pp → dπ+π0 reaction at Tp = 1.1 GeV we demonstrate that, indeed, the ABC effect does not occur in the vector-isovector ππ channel (ρ channel) despite the fact that the ΔΔ excitation is oberved to be the dominant reaction process. We also show that this reaction is well described by a t-channel ΔΔ excitation with the subsequent decay into the vector-isovector ππ channel given by the ρ channel operator. [ABSTRACT FROM AUTHOR]

Published
2009

44. 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., and Keleta, S.

Subjects
RESONANCE, PARTICLES (Nuclear physics), SCATTERING (Physics), MASS spectrometry, PHASE shift (Nuclear physics)
Abstract

In most investigations the Roper resonance is sensed only very indirectly via complex partial-wave analyses. We find indications for its excitation in the invariant nπ+ mass spectrum of the pp → npπ+ reaction at M ≈ 1360 MeV with a width of ≈ 150 MeV . The values fit very favorably to the most recent phase shift results as well as to the observations at BES. In the near-threshold two-pion production pp → ppπ0π0 , where the Roper excitation and its subsequent decays via the routes N * → Δπ → Nππ and N * → Nσ are the only dominant processes, we find its direct decay into the Nσ channel to be the by far dominating decay process --in favor of a monopole excitation of the Roper resonance. [ABSTRACT FROM AUTHOR]

Published
2008
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45. Two-pion production in proton–proton collisions — experimental total cross sections and their isospin decomposition

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., and Kullander, S.

Subjects
*PION production, *PROTON-proton interactions, *NUCLEAR cross sections, *ISOBARIC spin, *CHEMICAL decomposition, *PARTICLE accelerators, *DIFFERENTIAL cross sections, *NUCLEAR excitation
Abstract

Abstract: The two-pion production in pp-collisions has been investigated at CELSIUS in exclusive measurements from threshold up to . Total and differential cross sections have been obtained for the channels , , and also . For intermediate incident energies , i.e. in the region which is beyond the Roper excitation but at the onset of ΔΔ excitation, the total cross section falls behind theoretical predictions by as much as an order of magnitude near 1.2 GeV, whereas the cross section is a factor of five larger than predicted. An isospin decomposition 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 . As possible candidates the and the are discussed. [Copyright &y& Elsevier]

Published
2009
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46. Exclusive measurement of two-pion production in the reaction

Author

Keleta, S., 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., Khakimova, O., Kren, F., and Kullander, S.

Subjects
*PHYSICAL measurements, *PION production, *NUCLEAR reactions, *MASS (Physics), *COLLISIONS (Nuclear physics), *NUCLEAR counters
Abstract

Abstract: The results from the first kinematically complete measurement of the reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar ππ-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 ππ-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 sub-processes. [Copyright &y& Elsevier]

Published
2009
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47. Abashian-Booth-Crowe effect in basic double-pionic fusion: a new resonance?

Author

Adlarson P, Adolph C, Augustyniak W, Baru V, Bashkanov M, Bednarski T, Bergmann FS, Berłowski M, Bhatt H, Brinkmann KT, Büscher M, Calén H, Clement H, Coderre D, Czerwiński E, Doroshkevich E, Ekström C, Engels R, Erven W, Eyrich W, Fedorets P, Föhl K, Fransson K, Goldenbaum F, Goslawski P, Grigoryev K, Grishina V, Gullström CO, Hampe J, Hanhart C, Heijkenskjöld L, Hejny V, Hinterberger F, Hodana M, Höistad B, Jacewicz M, Janusz M, Jany A, Jany BR, 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, Kullander S, Kupść A, Lalwani K, Lorentz B, Magiera A, Maier R, Marciniewski P, Mariański B, Mikirtychiants M, Moskal P, Morsch HP, Nandi BK, Niedźwiecki S, Ohm H, Passfeld A, Pauly C, del Rio EP, Petukhov Y, Piskunov N, Pluciński P, Podkopał P, Povtoreyko A, Prasuhn D, Pricking A, Pysz K, Rausmann T, Redmer CF, Ritman J, Roy A, Ruber RJ, Rudy Z, Sawant S, 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, Ströher H, Szczurek A, Täschner A, Tolba T, Trzciński A, Varma R, Vlasov P, Wagner GJ, Węglorz W, Winnemöller A, Wirzba A, Wolke M, Wrońska A, Wüstner P, Wurm P, Yuan X, Yurev L, Zabierowski J, Zheng C, Zieliński MJ, Zipper W, Złomańczuk J, and Zuprański P

Abstract

We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn→dπ(0)π(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the ππ-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ΔΔ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m=2.37  GeV, Γ≈70  MeV and I(J(P))=0(3(+)) in both pn and ΔΔ systems. Necessary further tests of the resonance interpretation are discussed.

Published
2011
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48. Double-pionic fusion of nuclear systems and the "ABC" effect: approaching a puzzle by exclusive and kinematically complete measurements.

Author

Bashkanov M, Bargholtz C, Berłowski M, Bogoslawsky D, Calén H, Clement H, Demiroers L, Doroshkevich E, Duniec D, Ekström C, Fransson K, Geren L, Gustafsson L, Höistad B, Ivanov G, Jacewicz M, Jiganov E, Johansson T, Khakimova O, Keleta S, Koch I, Kren F, Kullander S, Kupść A, Lindberg K, Marciniewski P, Meier R, Morosov B, Pauly C, Pettersson H, Petukhov Y, Povtorejko A, Pricking A, Ruber RJ, Schönning K, Scobel W, Shwartz B, Skorodko T, Sopov V, Stepaniak J, Tegner PE, Thörngren-Engblom P, Tikhomirov V, Turowiecki A, Wagner GJ, Wolke M, Zabierowski J, Zartova I, and Złomanczuk J

Abstract

The ABC effect-a puzzling low-mass enhancement in the pipi 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-->dpi;{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 (pipi)_{I=L=0} channel phenomenon associated with both a resonancelike energy dependence in the integral cross section and the formation of a DeltaDelta system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.

Published
2009
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