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1. Corrigendum to 'Isoscalar single-pion production in the region of Roper and d⁎(2380) resonances' [Phys. Lett. B 774 (2017) 599]

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Physics, QC1-999
Published: 2020
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2. Search for η mesic 3He with the WASA-at-COSY facility in the pd→3He2γ and pd→3He6γ reactions

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, S.D. Bass, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, L. Heijkenskjöld, V. Hejny, S. Hirenzaki, L. Jarczyk, T. Johansson, B. Kamys, N.G. Kelkar, G. Kemmerling, A. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, J. Ritman, A. Roy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti–Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Physics, QC1-999
Abstract: We report on the experimental search for the bound state of an η meson and He3 nucleus performed using the WASA-at-COSY detector setup. In order to search for the η-mesic nucleus decay, the pd→3He2γ and pd→3He6γ channels have been analysed. These reactions manifest the direct decay of the η meson bound in a He3 nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to a 3He-η nucleus width Γ above 20 MeV and binding energy Bs between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the η-mesic He3 nucleus formation followed by the η meson decay which varies between 2 nb and 15 nb depending on possible bound state parameters. Keywords: η-mesic nuclei, η meson
Published: 2020
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3. Role of the d⁎(2380) dibaryon in NN interaction

Author: V.I. Kukulin, O.A. Rubtsova, M.N. Platonova, V.N. Pomerantsev, and H. Clement
Subjects: Physics, QC1-999
Abstract: It is demonstrated for the first time that the dibaryon resonance d⁎(2380) discovered reliably in the numerous experiments at the WASA@COSY facility (Jülich FZ) determines almost completely (when supplemented with the peripheral one-pion exchange) NN scattering phase shifts and inelasticities in the coupled partial-wave channels D33–G33 not only near the resonance position, but also in a broad energy range from zero up to about 1 GeV. Keywords: Nucleon-nucleon interaction, Dibaryon resonances
Published: 2020
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4. Determination of N* amplitudes from associated strangeness production in p+p collisions

Author: R. Münzer, L. Fabbietti, E. Epple, S. Lu, P. Klose, F. Hauenstein, N. Herrmann, D. Grzonka, Y. Leifels, M. Maggiora, D. Pleiner, B. Ramstein, J. Ritman, E. Roderburg, P. Salabura, A. Sarantsev, Z. Basrak, P. Buehler, M. Cargnelli, R. Čaplar, H. Clement, O. Czerwiakowa, I. Deppner, M. Dželalija, W. Eyrich, Z. Fodor, P. Gasik, I. Gašparić, A. Gillitzer, Y. Grishkin, O.N. Hartmann, K.D. Hildenbrand, B. Hong, T.I. Kang, J. Kecskemeti, Y.J. Kim, M. Kirejczyk, M. Kiš, P. Koczon, R. Kotte, A. Lebedev, A. Le Fèvre, J.L. Liu, V. Manko, J. Marton, T. Matulewicz, K. Piasecki, F. Rami, A. Reischl, M.S. Ryu, P. Schmidt, Z. Seres, B. Sikora, K.S. Sim, K. Siwek-Wilczyńska, V. Smolyankin, K. Suzuki, Z. Tymiński, P. Wagner, I. Weber, E. Widmann, K. Wiśniewski, Z.G. Xiao, T. Yamasaki, I. Yushmanov, P. Wintz, Y. Zhang, A. Zhilin, V. Zinyuk, and J. Zmeskal
Subjects: Physics, QC1-999
Abstract: We present the first determination of the energy-dependent amplitudes of N⁎ resonances extracted from their decay in KΛ pairs in p+p→pK+Λ reactions. A combined Partial Wave Analysis of seven data samples with exclusively reconstructed p+p→pK+Λ events measured by the COSY-TOF, DISTO, FOPI and HADES Collaborations in fixed target experiments at kinetic energies between 2.14 to 3.5 GeV is used to determine the amplitude of the resonant and non-resonant contributions into the associated strangeness final state. The contribution of seven N⁎ resonances with masses between 1650 MeV/c2 and 1900 MeV/c2 for an excess energy between 0 and 600 MeV has been considered. The Σ–p cusp and final state interactions for the p–Λ channel are also included as coherent contributions in the PWA. The N⁎ contribution is found to be dominant with respect to the phase space emission of the pKΛ+ final state at all energies demonstrating the important role played by both N⁎ and interference effects in hadron–hadron collisions. Keywords: Partial wave analysis, Resonance, Hadrons, Strangeness, Scattering length, Hyperon–nucleon interaction
Published: 2018
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5. Search for C violation in the decay η → π0e+e− with WASA-at-COSY

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, A. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, M. Żurek, and A. Wirzba
Subjects: Physics, QC1-999
Abstract: We report on the search for the rare decay η→π0e+e− which is of interest to study C violation in the electromagnetic interaction which would indicate contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Jülich, Germany. In total 3×107 events of the reaction pd→3Heη have been recorded at an excess energy of Q=59.8MeV. Based on this data set the C parity violating decay η→π0γ⁎→π0e+e− via a single-photon intermediate state has been searched for, resulting in new upper limits of Γ(η→π0e+e−)/Γ(η→π+π−π0)
Published: 2018
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6. Total and differential cross sections of η-production in proton–deuteron fusion for excess energies between Qη = 13 MeV and Qη = 81 MeV

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, A. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, M. Żurek, and C. Wilkin
Subjects: Physics, QC1-999
Abstract: New data on both total and differential cross sections of the production of η mesons in proton–deuteron fusion to He3η in the excess energy region 13.6MeV≤Qη≤80.9MeV are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Jülich, using a proton beam at 15 different beam momenta between pp=1.60GeV/c and pp=1.74GeV/c. While significant structure of the total cross section is observed in the energy region 20MeV≲Qη≲60MeV, a previously reported sharp variation around Qη≈50MeV cannot be confirmed. Angular distributions show the typical forward-peaking that was noted earlier. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a wide interval. Keywords: Meson production, Proton–deuteron interactions, η meson
Published: 2018
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7. Importance of d-wave contributions in the charge symmetry breaking reaction dd→4Heπ0

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, C. Hanhart, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Physics, QC1-999
Abstract: This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd→4Heπ0 using the WASA-at-COSY detector setup at an excess energy of Q=60MeV. The determined differential cross section can be parametrized as dσ/dΩ=a+bcos2⁡θ⁎, where θ⁎ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a=(1.55±0.46(stat)+0.32−0.8(syst))pb/sr and b=(13.1±2.1(stat)−2.7+1.0(syst))pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Δ isobar to the dd→4Heπ0 reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions. Keywords: Charge symmetry breaking, Deuteron–deuteron interactions, Pion production
Published: 2018
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8. Isoscalar single-pion production in the region of Roper and d⁎(2380) resonances

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, W. Parol, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Single-pion production, Isoscalar part, Roper resonance, Dibaryon resonance, Physics, QC1-999
Abstract: Exclusive measurements of the quasi-free pn→ppπ− and pp→ppπ0 reactions have been performed by means of pd collisions at Tp=1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region Tp=0.95–1.3 GeV (s=2.3–2.46 GeV), which includes the regions of Δ(1232), N⁎(1440) and d⁎(2380) resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below Tp=1 GeV. We observe a substantial increase of this cross section around 1 GeV, which can be related to the Roper resonance N⁎(1440), the strength of which shows up isolated from the Δ resonance in the isoscalar (Nπ)I=0 invariant-mass spectrum. No evidence for a decay of the dibaryon resonance d⁎(2380) into the isoscalar (NNπ)I=0 channel is found. An upper limit of 180 μb (90% C.L.) corresponding to a branching ratio of 9% has been deduced.
Published: 2017
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9. Measurement of the ω→π+π−π0 Dalitz plot distribution

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Decays of other mesons, Meson–meson interactions, Light mesons, Physics, QC1-999
Abstract: Using the production reactions pd→He3ω and pp→ppω, the Dalitz plot distribution for the ω→π+π−π0 decay is studied with the WASA detector at COSY, based on a combined data sample of (4.408±0.042)×104 events. The Dalitz plot density is parametrised by a product of the P-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables Z and ϕ. For the first time, a deviation from pure P-wave phase space is observed with a significance of 4.1σ. The deviation is parametrised by a linear term 1+2αZ, with α determined to be +0.147±0.036, consistent with the expectations of ρ-meson-type final-state interactions of the P-wave pion pairs.
Published: 2017
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10. Search for an isospin I=3 dibaryon

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, E. Czerwiński, K. Demmich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, A. Goswami, K. Grigoryev, C.-O. Gullström, L. Heijkenskjöld, V. Hejny, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, G. Khatri, A. Khoukaz, O. Khreptak, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, H.-P. Morsch, P. Moskal, H. Ohm, E. Perez del Rio, N.M. Piskunov, D. Prasuhn, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, O. Rundel, S. Sawant, S. Schadmand, I. Schätti-Ozerianska, T. Sefzick, V. Serdyuk, B. Shwartz, K. Sitterberg, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, A. Yamamoto, J. Zabierowski, M.J. Zieliński, A. Zink, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Physics, QC1-999
Abstract: Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance d⁎(2380) with I(JP)=0(3+) there should also exist a dibaryon resonance with mirrored quantum numbers I(JP)=3(0+). We report here on a search for such a NN-decoupled state in data on the pp→ppπ+π+π−π− reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280–2500 MeV. Keywords: Dibaryons, Four-pion production
Published: 2016
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11. Measurement of the np→npπ0π0 reaction in search for the recently observed d⁎(2380) resonance

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, D. Coderre, E. Czerwiński, K. Demmich, E. Doroshkevich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, C.-O. Gullström, F. Hauenstein, L. Heijkenskjöld, V. Hejny, B. Höistad, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, A. Khoukaz, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, M. Mikirtychiants, H.-P. Morsch, P. Moskal, H. Ohm, I. Ozerianska, E. Perez del Rio, N.M. Piskunov, P. Podkopał, D. Prasuhn, A. Pricking, D. Pszczel, K. Pysz, A. Pyszniak, J. Ritman, A. Roy, Z. Rudy, S. Sawant, S. Schadmand, T. Sefzick, V. Serdyuk, B. Shwartz, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Täschner, A. Trzciński, R. Varma, G.J. Wagner, M. Wolke, A. Wrońska, P. Wüstner, P. Wurm, A. Yamamoto, J. Zabierowski, M.J. Zieliński, A. Zink, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Physics, QC1-999
Abstract: Exclusive measurements of the quasi-free np→npπ0π0 reaction have been performed by means of dp collisions at Td=2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region s=(2.35–2.46) GeV, which includes the region of the ABC effect and its associated d⁎(2380) resonance. Adding the d⁎ resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of Fäldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the π0π0-invariant mass spectrum, is found to be very modest – if present at all, which might pose a problem to some of its interpretations. Keywords: Two-pion production, ABC effect and resonance structure, Dibaryon resonance
Published: 2015
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12. Charge symmetry breaking in dd→He4π0 with WASA-at-COSY

Author: P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F.S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, D. Coderre, E. Czerwiński, K. Demmich, E. Doroshkevich, R. Engels, A. Erven, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, C.-O. Gullström, C. Hanhart, F. Hauenstein, L. Heijkenskjöld, V. Hejny, B. Höistad, N. Hüsken, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F.A. Khan, A. Khoukaz, D.A. Kirillov, S. Kistryn, H. Kleines, B. Kłos, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, M. Mikirtychiants, H.-P. Morsch, P. Moskal, H. Ohm, I. Ozerianska, E. Perez del Rio, N.M. Piskunov, P. Podkopał, D. Prasuhn, A. Pricking, D. Pszczel, K. Pysz, A. Pyszniak, C.F. Redmer, J. Ritman, A. Roy, Z. Rudy, S. Sawant, S. Schadmand, T. Sefzick, V. Serdyuk, B. Shwartz, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, A. Täschner, A. Trzciński, R. Varma, M. Wolke, A. Wrońska, P. Wüstner, P. Wurm, A. Yamamoto, L. Yurev, J. Zabierowski, M.J. Zieliński, A. Zink, J. Złomańczuk, P. Żuprański, and M. Żurek
Subjects: Physics, QC1-999
Abstract: Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext) pb and first data on the differential cross section are consistent with s-wave pion production. Keywords: Charge symmetry breaking, Deuteron–deuteron interactions, Pion production
Published: 2014
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13. Search for the η mesic He3 in the pd→dpπ0 reaction with the WASA-at-COSY facility

Author: M. Bashkanov, Markus Büscher, Izabela Ciepał, A. Erven, A. Goswami, A.E. Bondar, H. P. Morsch, P. Fedorets, Hans Stockhorst, Akira Yamamoto, Frank Goldenbaum, B. Mariański, Steven D. Bass, Rolf Stassen, K. Fransson, Hans Calén, Magdalena Skurzok, S. Schadmand, A. Khoukaz, Satoru Hirenzaki, Günter Kemmerling, Marcin Zieliński, P. Kulessa, W. Eyrich, A. Kupść, N. Hüsken, Di. Kirillov, W. Augustyniak, D. Pszczel, H. Ohm, K. Pysz, B. Kamys, T. Sefzick, Stanisław Kistryn, T. Johansson, Wiktor Parol, W. Erven, R. Engels, P. Wüstner, Lena Heijkenskjöld, D. Prasuhn, Paweł Moskal, G. Sterzenbach, B. Lorentz, M. Żurek, D. Lersch, B. Kłos, P. Adlarson, N. G. Kelkar, V. Hejny, K. Föhl, H. Clement, N.M. Piskunov, B. Shwartz, J. Stepaniak, Jozef Zlomanczuk, M. Berłowski, H. Ströher, Pawel Marciniewski, Eryk Czerwiński, T. Skorodko, Harald Kleines, J. Ritman, S. Sawant, V. Serdyuk, A. Magiera, Jerzy Smyrski, Oleksandr Rundel, E. Stephan, K. Lalwani, Wojciech Krzemien, J. Zabierowski, Antoni Szczurek, V. Sopov, Ankhi Roy, Aleksander Khreptak, K. Grigoryev, R. Maier, Aleksandra Wrońska, E. Perez del Rio, K. Demmich, F. S. Bergmann, and Magnus Wolke
Subjects: Excitation function, Physics, Meson production, Proton, 010308 nuclear & particles physics, chemistry.chemical_element, Resonance, 01 natural sciences, Nuclear physics, chemistry, 0103 physical sciences, Bound state, Pi, High Energy Physics::Experiment, Production (computer science), Nuclear Experiment, 010306 general physics, Helium
Abstract: The excitation function for the $pd\rightarrow$ $d p \pi^{0}$ reaction has been measured by WASA-at-COSY experiment with the aim of searching for $^{3}\hspace{-0.03cm}\mbox{He}$-$\eta$ mesic nuclei. The measurement in the vicinity of $\eta$ meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the $\eta$-mesic Helium decays via the formation of an intermediate N$^{*}$(1535) resonance. No direct signal of the $\eta$-mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the $pd\rightarrow$ $(^{3}\hspace{-0.03cm}\mbox{He}$-$\eta)_{bound} \rightarrow$ $d p \pi^{0}$ process. It varies between 13 nb to 24 nb for the bound state with width in the range $\Gamma \in (5,50)$ MeV.
Published: 2020

14. Nature of $$\varvec{S}$$-wave $$\varvec{NN}$$ interaction and dibaryon production at nucleonic resonance thresholds

Author: T. Skorodko, V. I. Kukulin, O. A. Rubtsova, V. N. Pomerantsev, M. N. Platonova, and H. Clement
Subjects: Physics, Nuclear and High Energy Physics, Particle physics, Roper resonance, Isovector, 010308 nuclear & particles physics, Scattering, Isoscalar, Nuclear Theory, Hadron, Resonance, 01 natural sciences, 0103 physical sciences, Nuclear Experiment, 010306 general physics, Energy (signal processing), Excitation
Abstract: Phase shifts and inelasticity parameters for NN scattering in the partial-wave channels $${}^3S_1$$ – $${}^3D_1$$ and $${}^1S_0$$ at energies $$T_\mathrm{lab}$$ from zero to about 1 GeV are described within a unified NN potential model assuming the formation of isoscalar and isovector dibaryon resonances near the $$NN^*(1440)$$ threshold. Evidence for these near-threshold resonances is actually found in the recent WASA experiments on single- and double-pion production in NN collisions. There, the excitation of the Roper resonance $$N^*(1440)$$ exhibits a structure in the energy dependence of the total cross section which corresponds to the formation of dibaryon states with $$I(J^\pi )=0(1^+)$$ and $$1(0^+)$$ at the $$NN^*(1440)$$ threshold. These two S-wave dibaryon resonances may provide new insight into the nature of the strong NN interaction at low and intermediate energies.
Published: 2020

15. Differential cross sections for neutron-proton scattering in the region of the d*(2380) dibaryon resonance

Author: C.-O. Gullström, Markus Büscher, D. Pszczel, P. Podkopał, Pawel Marciniewski, S. Sawant, Paweł Moskal, R. Varma, P. Fedorets, I. Ozerianska, R. Maier, A. Švarc, J. Ritman, W. Eyrich, T. Sefzick, V. Serdyuk, P. Goslawski, E. Stephan, Jerzy Smyrski, P. Kulessa, N. Hüsken, B. Kamys, V. Hejny, K. Föhl, R. Engels, A. Pricking, P. Wüstner, H. Clement, Günter Kemmerling, A. Kupść, M. Mikirtychiants, A. Pyszniak, W. Augustyniak, D. Lersch, Izabela Ciepał, A. Goswami, Magdalena Skurzok, M. Bashkanov, Frank Goldenbaum, M. Krapp, K. Demmich, K. Pysz, B. Kłos, A. Magiera, Ferdous Khan, J. Zabierowski, Akira Yamamoto, Hans Stockhorst, M. Berłowski, A. Erven, H. Ströher, W. Erven, G. Sterzenbach, Antoni Szczurek, B. Lorentz, Rolf Stassen, Tord Johansson, K. Fransson, H. P. Morsch, Zbigniew Rudy, T. Skorodko, V. Sopov, H. Ohm, K. Grigoryev, A. Trzcinski, A. Khoukaz, S. Schadmand, P. Żuprański, A. Zink, Jozef Zlomanczuk, B. Mariański, R. Siudak, A. Täschner, I. I. Strakovsky, E. Doroshkevich, Aleksandra Wrońska, A. Jany, K. Lalwani, Eryk Czerwiński, Hans Calén, Stanisław Kistryn, W. Bardan, W. J. Briscoe, E. Perez del Rio, Ankhi Roy, Wojciech Krzemien, M. Hodana, J. Stepaniak, C. F. Redmer, F. S. Bergmann, Magnus Wolke, Harald Kleines, Di. Kirillov, F. Hauenstein, Lena Heijkenskjöld, D. Prasuhn, P. Wurm, Patrik Adlarson, Bo Höistad, D. Coderre, L. Yurev, Benedykt R. Jany, Himani Bhatt, N.M. Piskunov, Ron L. Workman, M. Żurek, and Marcin Zieliński
Subjects: Physics, Nuclear physics, Range (particle radiation), Hydrogen, chemistry, Deuterium, Scattering, chemistry.chemical_element, Neutron, Nuclear Experiment, Resonance (particle physics), Beam (structure), Differential (mathematics)
Abstract: Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized np scattering performed in the energy region of the d*(2380) dibaryon resonance covering the range of beam energies Tn=0.98−1.29 GeV (s=2.32−2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp→np+pspectator. In this way the np differential cross section σ(Θ) was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power Ay(Θ) measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled D33-G33 waves.
Published: 2020

16. Role of the d⁎(2380) dibaryon in NN interaction

Author: M. N. Platonova, H. Clement, V. N. Pomerantsev, O. A. Rubtsova, and V. I. Kukulin
Subjects: Physics, Nuclear and High Energy Physics, Range (particle radiation), 010308 nuclear & particles physics, Scattering, Nuclear Theory, Phase (waves), 01 natural sciences, Resonance (particle physics), lcsh:QC1-999, Nuclear physics, Position (vector), 0103 physical sciences, 010306 general physics, Nuclear Experiment, lcsh:Physics
Abstract: It is demonstrated for the first time that the dibaryon resonance d ⁎ ( 2380 ) discovered reliably in the numerous experiments at the WASA@COSY facility (Julich FZ) determines almost completely (when supplemented with the peripheral one-pion exchange) NN scattering phase shifts and inelasticities in the coupled partial-wave channels D 3 3 – G 3 3 not only near the resonance position, but also in a broad energy range from zero up to about 1 GeV.
Published: 2020

17. Dibaryons: Molecular versus Compact Hexaquarks

Author: T. Skorodko and H. Clement
Subjects: Quark, Physics, Nuclear and High Energy Physics, Particle physics, Current (mathematics), Nuclear Theory, 010308 nuclear & particles physics, Physics beyond the Standard Model, Hexaquark, FOS: Physical sciences, Astronomy and Astrophysics, State (functional analysis), 01 natural sciences, High Energy Physics - Experiment, Nuclear Theory (nucl-th), High Energy Physics - Phenomenology, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), 0103 physical sciences, Nuclear Experiment (nucl-ex), 010306 general physics, Instrumentation, Nuclear theory, Nuclear Experiment
Abstract: Hexaquarks constitute a natural extension of complex quark systems, just as tetra- and pentaquarks do. To this end, the current status of in both experiment and theory is reviewed. Recent high-precision measurements in the nucleon-nucleon channel and analyses thereof have established as an indisputable resonance in the long-sought dibaryon channel. Important features of this state are its narrow width and deep binding relative to the threshold. Its decay branchings favor theoretical calculations predicting a compact hexaquark nature of this state. We review the current status of experimental and theoretical studies on as well as new physics aspects it may bring in future. In addition, we review the situation at the and thresholds, where evidence for a number of resonances of presumably molecular nature has been found – similar to the situation in charmed and beauty sectors. Finally, we briefly discuss the situation of dibaryon searches in the flavored quark sectors.
Published: 2020
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18. Three-nucleon dynamics in dp breakup collisions using the WASA detector at COSY-Jülich

Author: Jozef Zlomanczuk, P. Kulessa, K. Pysz, A. Kupść, Ankhi Roy, J. Zabierowski, A. Trzcinski, Antoni Szczurek, B. Kłos, Aleksandra Wrońska, E. Perez del Rio, A. Deltuva, T. Sefzick, R. Maier, D. Lersch, W. Augustyniak, D. Pszczel, Frank Goldenbaum, S. Schadmand, Eryk Czerwiński, K. Lalwani, S. Sawant, H. P. Morsch, M. Żurek, Harald Kleines, W. Erven, A. Kozela, Jacek Golak, Oleksandr Rundel, Wojciech Krzemien, B. Kamys, P. Żuprański, R. Skibiński, Marcin Zieliński, R. Engels, P. Wüstner, B. Shwartz, J. Stepaniak, Paweł Moskal, W. Eyrich, E. Stephan, A. Magiera, F. S. Bergmann, A. Wilczek, Magnus Wolke, N. Hüsken, V. Sopov, W. Bardan, B. Mariański, M. Berłowski, Patrik Adlarson, Magdalena Skurzok, Hans Calén, Akira Yamamoto, M. Bashkanov, T. Skorodko, Pawel Marciniewski, A. Erven, H. Ströher, K. Fransson, K. Demmich, J. Ritman, Tord Johansson, Henryk Witała, V. Serdyuk, Jerzy Smyrski, K. Grigoryev, L. Jarczyk, A. Khoukaz, Izabela Ciepał, A. Goswami, Hans Stockhorst, Rolf Stassen, G. Sterzenbach, B. Lorentz, Stanisław Kistryn, Lena Heijkenskjöld, D. Prasuhn, V. Hejny, K. Föhl, Günter Kemmerling, Markus Büscher, I. Skwira-Chalot, P. Fedorets, Wiktor Parol, N.M. Piskunov, H. Clement, Di. Kirillov, A.E. Bondar, and Aleksander Khreptak
Subjects: Physics, Scattering cross-section, дейтроны, нуклоны, 010308 nuclear & particles physics, Dynamics (mechanics), Detector, Nuclear Theory, Breakup, 01 natural sciences, dp-развал, Nuclear physics, Deuterium, 0103 physical sciences, Physics::Accelerator Physics, ddc:530, протоны, 010306 general physics, Nucleon, Nuclear Experiment, Beam energy
Abstract: The differential cross section for the 1H(d,pp)n breakup reaction at deuteron beam energy of 340 MeV has been measured with the use of the WASA detector at COSY-Jülich. The set of proton-proton coincidences registered at the Forward Detector has been analyzed on a dense grid of kinematic variables, giving in total around 5600 data points. The cross-section data are compared to theoretical predictions based on the state-of-the-art nucleon-nucleon potentials, combined with a three-nucleon force or the Coulomb interaction or carried out in a relativistic regime.
Published: 2020

19. Search for C violation in the decay η → π0e+e− with WASA-at-COSY

Author: B.A. Shwartz, A. Khoukaz, B. Kamys, D. Lersch, Frank Goldenbaum, P. Wüstner, A. Trzcinski, Oleksandr Rundel, E. Stephan, W. Bardan, Jozef Zlomanczuk, Di. Kirillov, P. Adlarson, Paweł Moskal, S. Sawant, H. Clement, P. Żuprański, T. Sefzick, J. Zabierowski, Magdalena Skurzok, A. Magiera, S. Schadmand, W. Eyrich, Aleksandra Wrońska, Antoni Szczurek, E. Perez del Rio, James Ritman, A. Khreptak, D. Pszczel, N. Hüsken, Pawel Marciniewski, Günter Kemmerling, J. Stepaniak, Hans Calén, M. Bashkanov, H. Ohm, A. Kuzmin, M. Żurek, M. Berłowski, Wiktor Parol, A. Pyszniak, W. Augustyniak, A. Erven, I. Schätti-Ozerianska, G. Khatri, K. Sitterberg, V. Serdyuk, Ankhi Roy, Jerzy Smyrski, Stanisław Kistryn, V. Hejny, T. Johansson, Kjell Fransson, V. Sopov, Izabela Ciepał, Akira Yamamoto, T. Skorodko, A. Kupść, A.E. Bondar, R. Maier, G. Sterzenbach, B. Lorentz, W. Erven, K. Pysz, P. Fedorets, B. Kłos, Andreas Wirzba, Lena Heijkenskjöld, H. Ströher, Hans Stockhorst, D. Prasuhn, N.M. Piskunov, Ralf Engels, Rolf Stassen, P. Kulessa, H. P. Morsch, Wojciech Krzemien, K. Lalwani, F. S. Bergmann, Magnus Wolke, Zbigniew Rudy, Eryk Czerwiński, Harald Kleines, K. Grigoryev, L. Jarczyk, A. Goswami, K. Demmich, Marcin Zieliński, B. Mariański, K. Föhl, C.-O. Gullström, and Markus Büscher
Subjects: Nuclear and High Energy Physics, Meson, Hadron, Elementary particle, cząstki elementarne, 01 natural sciences, Standard Model, fizyka jądrowa, бозоны, Pion, 0103 physical sciences, Intermediate state, detektor WASA, ddc:530, Nuclear Experiment, 010306 general physics, Boson, Physics, 010308 nuclear & particles physics, фотоны, распад, respiratory system, lcsh:QC1-999, 3. Good health, детекторы, cardiovascular system, мезоны, Physical chemistry, High Energy Physics::Experiment, Radioactive decay, lcsh:Physics, circulatory and respiratory physiology
Abstract: We report on the search for the rare decay η → π 0 e + e − which is of interest to study C violation in the electromagnetic interaction which would indicate contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Julich, Germany. In total 3 × 10 7 events of the reaction p d → 3 He η have been recorded at an excess energy of Q = 59.8 MeV . Based on this data set the C parity violating decay η → π 0 γ ⁎ → π 0 e + e − via a single-photon intermediate state has been searched for, resulting in new upper limits of Γ ( η → π 0 e + e − ) / Γ ( η → π + π − π 0 ) 3.28 × 10 − 5 and Γ ( η → π 0 e + e − ) / Γ ( η → all ) 7.5 × 10 − 6 ( CL = 90 % ), respectively.
Published: 2018

20. Search for η-mesic He4 in the dd→He3nπ0 and dd→He3pπ− reactions with the WASA-at-COSY facility

Author: M. Bashkanov, A. Erven, K. Sitterberg, B. Lorentz, Frank Goldenbaum, A. Trzcinski, D. Lersch, H. Ströher, C.-O. Gullström, Markus Büscher, Jozef Zlomanczuk, Günter Kemmerling, A.E. Bondar, K. Grigoryev, H. Bhatt, R. Stassen, H. P. Morsch, Marcin Zieliński, A. Kuzmin, P. Adlarson, L. Jarczyk, T. Johansson, Rudolf Maier, H. Ohm, W. Eyrich, Aleksandra Wrońska, E. Perez del Rio, M. Berłowski, J. Zabierowski, A. Magiera, G. Sterzenbach, A. Goswami, P. Żuprański, B. Kłos, Di. Kirillov, K. Demmich, N. Hüsken, B. Mariański, P. Kulessa, V. Sopov, A. Pyszniak, W. Augustyniak, Zbigniew Rudy, Antoni Szczurek, K. Pysz, P. Fedorets, H. Clement, W. Erven, D. Pszczel, Hans Calén, Izabela Ciepał, O. Khreptak, T. Skorodko, Eryk Czerwiński, F. S. Bergmann, Magnus Wolke, S. Schadmand, T. Sefzick, Oleksandr Rundel, Magdalena Skurzok, Kjell Fransson, I. Schätti-Ozerianska, Harald Kleines, H. Stockhorst, N. G. Kelkar, K. Föhl, Stanisław Kistryn, J. Stepaniak, E. Stephan, W. Bardan, N.M. Piskunov, M. Żurek, Paweł Moskal, Pawel Marciniewski, Lena Heijkenskjöld, K. Lalwani, Wojciech Krzemien, G. Khatri, S. Sawant, Akira Yamamoto, A. Kupść, R. Engels, D. Prasuhn, J. Ritman, Ankhi Roy, V. Serdyuk, Jerzy Smyrski, B. Kamys, P. Wüstner, R. Varma, V. Hejny, B.A. Shwartz, and A. Khoukaz
Subjects: Excitation function, Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Scattering, 01 natural sciences, Momentum, Deuterium, Isospin, 0103 physical sciences, Bound state, Atomic physics, 010306 general physics, Nucleon, Excitation
Abstract: The search for He 4 - η bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the d d → He 3 n π 0 and d d → He 3 p π − processes. The deuteron beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the d d → He 4 η reaction ranging from Q = − 70 MeV to Q = 30 MeV . The luminosity was determined based on the d d → He 3 n reaction and the quasi-free proton–proton scattering via d d → p p n s p e c t a t o r n s p e c t a t o r reactions. The excitation functions, determined independently for the measured reactions, do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in d d → ( He 4 - η ) b o u n d → He 3 n π 0 and d d → ( He 4 - η ) b o u n d → He 3 p π − processes were determined taking into account the isospin relation between the both of the considered channels. The results of the analysis depend on the assumptions of the N ⁎ (1535) momentum distribution in the anticipated mesic- He 4 . Assuming, as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in He 4 , we determined that (for the mesic bound state width in the range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for n π 0 and p π − channels, respectively. However, based on the recent theoretical findings of the N ⁎ (1535) momentum distribution in the N ⁎ - He 3 nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for n π 0 and p π − channels respectively.
Published: 2017

21. Examination of the production of an isotensor dibaryon in the pp→ppπ+π− reaction

Author: Zbigniew Rudy, Akira Yamamoto, O. Khreptak, A. Khoukaz, Eryk Czerwiński, B. Kamys, P. Żuprański, K. Fransson, Harald Kleines, Oleksandr Rundel, R. Engels, D. Lersch, P. Wüstner, H. P. Morsch, H. Clement, Hans Calén, E. Stephan, Jozef Zlomanczuk, T. Sefzick, W. Erven, A.E. Bondar, W. Eyrich, Wiktor Parol, Markus Büscher, M. Bashkanov, N. Hüsken, Pawel Marciniewski, A. Erven, Paweł Moskal, K. Pysz, M. Berłowski, D. Pszczel, A. Magiera, P. Fedorets, J. Ritman, T. Skorodko, Izabela Ciepał, A. Goswami, Di. Kirillov, B. Mariański, V. Serdyuk, H. Ströher, Stanisław Kistryn, P. Kulessa, Jerzy Smyrski, V. Hejny, K. Föhl, I. Schätti-Ozerianska, A. Trzcinski, S. Schadmand, Hans Stockhorst, B. Shwartz, J. Stepaniak, N.M. Piskunov, Lena Heijkenskjöld, W. Augustyniak, D. Prasuhn, V. Sopov, Rolf Stassen, G. Sterzenbach, B. Lorentz, Wojciech Krzemien, W. Bardan, Günter Kemmerling, J. Zabierowski, Antoni Szczurek, Aleksandra Wrońska, Ankhi Roy, E. Perez del Rio, M. Żurek, Marcin Zieliński, R. Maier, K. Grigoryev, L. Jarczyk, S. Sawant, F. S. Bergmann, Magnus Wolke, K. Demmich, K. Lalwani, A. Kupść, T. Johansson, B. Kłos, P. Adlarson, Magdalena Skurzok, H. Ohm, and Frank Goldenbaum
Subjects: Nuclear physics, Physics, Cross section (physics), Pion, Meson, 010308 nuclear & particles physics, Isospin, 0103 physical sciences, 010306 general physics, 7. Clean energy, 01 natural sciences, Resonance (particle physics)
Abstract: The quasifree pp → ppπ+π− reaction has been measured by means of pd collisions at Tp = 1.2 GeV using the WASA detector setup at COSY enabling exclusive and kinematically complete measurements. Total and differential cross sections have been extracted for the energy region Tp = 1.08–1.36 GeV (√s = 2.35–2.46 GeV) covering thus the regions of N∗(1440) and (1232)(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange as well as isospin relations based on the pp → ppπ0π0 data underpredict substantially the measured total cross section. The calculations are also at variance with specific experimental differential cross sections. An isotensor N dibaryon resonance with I (J P ) = 2(1+) produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong [Phys. Rev. Lett. 13, 815 (1964)] and more recently calculated by A. Gal and H. Garcilazo [Nucl. Phys. A 928, 73 (2014)].
Published: 2019

22. Pion production in nucleon-nucleon collisions and the issue of dibaryons

Author: T. Skorodko, H. Clement, and M. Bashkanov
Subjects: Physics, Particle physics, 010308 nuclear & particles physics, Branching fraction, Scattering, QC1-999, Nuclear Theory, Hexaquark, Observable, 01 natural sciences, Pion, 0103 physical sciences, 010306 general physics, Nucleon, Nuclear Experiment
Abstract: Pion production in nucleon-nucleon collisions is tightly connected with the issue of dibaryons. After having established the existence of the narrow dibaryon resonance d* (2380) with I(JP) = 0(3+) by two-pion production and elastic proton-neutron scattering experiments, the discussion focuses now on its structure, whether it is a dilute molecular-like or a compact hexaquark object. These scenarios are confronted with experimental branching ratios and other observables. New WASA data for the pp → ppπ+π− reaction give evidence for the existence of an isotensor ΔN threshold state with JP = 1+ as calculated recently by Gal and Garcilazo and predicted earlier by Dyson and Xuong. New ANKE results suggest the dibaryon spectrum to be richer than expected.
Published: 2019

23. Search for an isospin I= 3 dibaryon

Author: A.E. Bondar, Izabela Ciepał, O. Khreptak, Hans Stockhorst, Pawel Marciniewski, Rolf Stassen, Frank Goldenbaum, M. Berłowski, A. Magiera, J. Stepaniak, Jozef Zlomanczuk, J. Ritman, T. Skorodko, W. Erven, Di. Kirillov, Oleksandr Rundel, A. Zink, Paweł Moskal, V. Serdyuk, H. Bhatt, W. Eyrich, P. Kulessa, H. P. Morsch, T. Sefzick, Jerzy Smyrski, B. Kamys, P. Żuprański, P. Wüstner, D. Lersch, E. Stephan, M. Żurek, C.-O. Gullström, N. Hüsken, Markus Büscher, Günter Kemmerling, S. Schadmand, Zbigniew Rudy, N.M. Piskunov, A. Pyszniak, W. Augustyniak, A. Kuzmin, Hans Calén, M. Bashkanov, Eryk Czerwiński, K. Pysz, P. Fedorets, H. Clement, G. Khatri, Ferdous Khan, Kjell Fransson, Rudolf Maier, V. Hejny, A. Erven, Stanisław Kistryn, Harald Kleines, Akira Yamamoto, A. Kupść, K. Sitterberg, W. Bardan, Lena Heijkenskjöld, D. Prasuhn, B.A. Shwartz, A. Khoukaz, R. Varma, G. Sterzenbach, B. Lorentz, Ralf Engels, J. Zabierowski, Ankhi Roy, K. Föhl, Antoni Szczurek, H. Ströher, A. Trzcinski, Wojciech Krzemien, V. Sopov, D. Pszczel, I. Schätti-Ozerianska, Marcin Zieliński, P. Adlarson, H. Ohm, B. Mariański, Aleksandra Wrońska, E. Perez del Rio, Magdalena Skurzok, F. S. Bergmann, Magnus Wolke, K. Grigoryev, L. Jarczyk, A. Goswami, K. Demmich, T. Johansson, B. Kłos, K. Lalwani, and S. Sawant
Subjects: Nuclear and High Energy Physics, Particle physics, Pion-Production, Gev/C, Nuclear Theory, Hadron, FOS: Physical sciences, 01 natural sciences, Pp Collisions, High Energy Physics - Experiment, Subatomär fysik, Nuclear physics, High Energy Physics - Experiment (hep-ex), dibaryons, Subatomic Physics, 0103 physical sciences, ddc:530, Nuclear Experiment (nucl-ex), Nuclear Experiment, 010306 general physics, Proton-Proton Interactions, Physics, Quantum chromodynamics, States, Decomposition, Four-pion production, Dibaryons, 010308 nuclear & particles physics, Resonance, Quantum number, lcsh:QC1-999, Energies, Delta, Resonances, Isospin, four-pion production, 24 Gev-C, Beam energy, lcsh:Physics
Abstract: Various theoretical calculations based on QCD or hadronic interactions predict that in addition to the recently observed dibaryon resonance d⁎(2380) with I(JP)=0(3+) there should also exist a dibaryon resonance with mirrored quantum numbers I(JP)=3(0+). We report here on a search for such a NN-decoupled state in data on the pp→ppπ+π+π−π− reaction. Since no clear-cut evidence has been found, we give upper limits for the production cross section of such a resonance in the mass range 2280–2500 MeV., This work has been supported by DFG (CL 214/3-1), STFC (ST/L00478X/1) and by the Polish National Science Center through grants Nos. DEC-2013/11/N/ST2/04152 and 2011/03/B/ST2/01847
Published: 2016

24. ABC effect and resonance d*(2380)

Author: M. Bashkanov, E. Doroshkevich, H. Clement, and T. Skorodko
Subjects: Physics, Nuclear and High Energy Physics, Fusion, 010308 nuclear & particles physics, Scattering, Nuclear Theory, State (functional analysis), Quantum number, 01 natural sciences, Resonance (particle physics), Synchrotron, law.invention, law, 0103 physical sciences, Nuclear fusion, Particle, Atomic physics, Nuclear Experiment, 010306 general physics
Abstract: A new state in the two-baryon system with mass 2380 MeV and width 80 MeV has been detected in the experiments at the Juelich Cooler Synchrotron (COSY). The new particle denoted now d*(2380) has quantum numbers I(J p ) = 0(3+). The total cross sections for the d and 4He fusion reactions show similar to each other resonance-like energy dependence. The resonance-like structure is sensed in the double-pionic fusion channels and polarized np scattering.
Published: 2017

25. Corrigendum to 'Isoscalar single-pion production in the region of Roper and d⁎(2380) resonances' [Phys. Lett. B 774 (2017) 599]

Author: A. Khoukaz, K. Grigoryev, P. Fedorets, P. Żuprański, P. Wüstner, R. Stassen, W. Eyrich, Wiktor Parol, B. Kamys, A. Bondar, Hans Calén, C.-O. Gullström, Aleksandra Wrońska, H. Clement, E. Perez del Rio, Kjell Fransson, A. Trzciński, M. Bashkanov, A. Pyszniak, W. Augustyniak, Izabela Ciepał, Magnus Wolke, V. Serdyuk, A. Magiera, Zbigniew Rudy, A. Yamamoto, H. Kleines, A. Kupść, Eryk Czerwiński, H.-P. Morsch, Pawel Marciniewski, A. Roy, Marcin Zieliński, H. Ohm, H. Stockhorst, K. Pysz, L. Jarczyk, G. Sterzenbach, P. Kulessa, Stanisław Kistryn, N.M. Piskunov, B. Shwartz, K. Sitterberg, B. Lorentz, K. Lalwani, K. Demmich, R. Varma, J. Ritman, W. Bardan, Lena Heijkenskjöld, G. Khatri, Paweł Moskal, D.A. Kirillov, Jerzy Smyrski, T. Sefzick, M. Büscher, F. Goldenbaum, G. Kemmerling, R. Maier, T. Johansson, B. Kłos, A. Kuzmin, D. Prasuhn, S. Sawant, F.S. Bergmann, A. Goswami, T. Skorodko, V. Hejny, N. Hüsken, J. Stepaniak, Himani Bhatt, S. Schadmand, D. Lersch, B. Mariański, V. Sopov, P. Adlarson, Oleksandr Rundel, Magdalena Skurzok, M. Berłowski, D. Pszczel, H. Ströher, R. Engels, I. Schätti-Ozerianska, W. Erven, J. Zabierowski, Wojciech Krzemien, E. Stephan, A. Szczurek, K. Föhl, A. Erven, M. Żurek, O. Khreptak, and Jozef Zlomanczuk
Subjects: Physics, Nuclear physics, Nuclear and High Energy Physics, Pion, Isoscalar, ddc:530, lcsh:Physics, lcsh:QC1-999
Published: 2020

26. Search for η mesic 3He with the WASA-at-COSY facility in the pd→3He2γ and pd→3He6γ reactions

Author: Jozef Zlomanczuk, A. Trzcinski, W. Bardan, A. Magiera, V. Hejny, R. Maier, S. Sawant, James Ritman, Aleksandra Wrońska, E. Perez del Rio, B. Kamys, K. Grigoryev, Izabela Ciepał, D. Pszczel, B. Mariański, P. Wüstner, B.A. Shwartz, A.E. Bondar, T. Sefzick, Akira Yamamoto, A. Kupść, Hans Stockhorst, I. Schätti–Ozerianska, V. Sopov, D. Lersch, Rolf Stassen, T. Johansson, L. Jarczyk, B. Kłos, G. Sterzenbach, B. Lorentz, Oleksandr Rundel, M. Żurek, S. Schadmand, Paweł Moskal, A. Goswami, Marcin Zieliński, E. Stephan, Wiktor Parol, Pawel Marciniewski, Ralf Engels, Di. Kirillov, P. Kulessa, W. Erven, H. Clement, Wojciech Krzemien, Satoru Hirenzaki, V. Serdyuk, M. Berłowski, Günter Kemmerling, Jerzy Smyrski, Stanisław Kistryn, W. Augustyniak, K. Föhl, Ankhi Roy, A. Khreptak, T. Skorodko, Lena Heijkenskjöld, D. Prasuhn, W. Eyrich, Magnus Wolke, Markus Büscher, J. Zabierowski, M. Bashkanov, N.M. Piskunov, Antoni Szczurek, N. G. Kelkar, A. Erven, H. Ströher, Eryk Czerwiński, Harald Kleines, K. Lalwani, Frank Goldenbaum, Steven D. Bass, P. Żuprański, Hans Calén, Kjell Fransson, K. Pysz, P. Fedorets, J. Stepaniak, H. P. Morsch, H. Ohm, P. Adlarson, and Magdalena Skurzok
Subjects: Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Nuclear Theory, Eta meson, Detector, 01 natural sciences, Nuclear physics, medicine.anatomical_structure, 0103 physical sciences, Bound state, medicine, Order (group theory), High Energy Physics::Experiment, Nuclear Experiment, 010306 general physics, Nucleus
Abstract: We report on the experimental search for the bound state of an eta meson and He-3 nucleus performed using the WASA-at-COSY detector setup. In order to search for the eta-mesic nucleus decay, the pd ...
Published: 2020

27. Backward single-pion production in the $ pd\rightarrow {}^{3}\mathrm{He} \pi^{0}$ p d → 3 He π 0 reaction with WASA-at-COSY

Author: Günter Kemmerling, Izabela Ciepał, A. Trzcinski, Aleksandra Wrońska, E. Perez del Rio, Hans Calén, Hans Stockhorst, W. Eyrich, Wojciech Krzemien, R. Maier, H. Ohm, D. Lersch, Rolf Stassen, N. Hüsken, Kjell Fransson, Jozef Zlomanczuk, K. Lalwani, G. Sterzenbach, P. Kulessa, Stanisław Kistryn, B. Lorentz, C. Wilkin, H. Clement, Lena Heijkenskjöld, Pawel Marciniewski, Ralf Engels, D. Prasuhn, Frank Goldenbaum, Oleksandr Rundel, B. Mariański, Paweł Moskal, B.A. Shwartz, A. Khoukaz, F. S. Bergmann, J. Zabierowski, Magnus Wolke, Magdalena Skurzok, N.M. Piskunov, T. Johansson, W. Erven, E. Stephan, H. Ströher, K. Föhl, A. Magiera, Antoni Szczurek, A. Kuzmin, Wiktor Parol, P. Żuprański, B. Kłos, D. Pszczel, James Ritman, S. Sawant, I. Schätti-Ozerianska, V. Serdyuk, A. Pyszniak, W. Augustyniak, V. Sopov, Jerzy Smyrski, K. Grigoryev, C.-O. Gullström, Markus Büscher, B. Kamys, M. Bashkanov, V. Hejny, Akira Yamamoto, P. Wüstner, A. Kupść, A. Erven, Marcin Zieliński, L. Jarczyk, W. Bardan, K. Sitterberg, P. Adlarson, A. Goswami, K. Demmich, S. Schadmand, G. Khatri, M. Berłowski, Ankhi Roy, T. Skorodko, T. Sefzick, Zbigniew Rudy, M. Żurek, Eryk Czerwiński, Harald Kleines, K. Pysz, P. Fedorets, J. Stepaniak, H. P. Morsch, Di. Kirillov, A. Khreptak, and A.E. Bondar
Subjects: Physics, Nuclear reaction, Nuclear and High Energy Physics, Meson, Proton, 010308 nuclear & particles physics, Hadron, Elementary particle, 01 natural sciences, 7. Clean energy, Nuclear physics, Pion, 0103 physical sciences, Production (computer science), Nuclear Experiment, 010306 general physics, Isotopes of helium
Abstract: New data on the production of single neutral pions in the $ pd\rightarrow {}^{3}\mathrm{He} \pi^{0}$ reaction are presented. For fifteen proton beam momenta between $ p_{p}=1.60$ GeV/c and $ p_{p}=1.74$ GeV/c, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
Published: 2018

28. Isotensor Dibaryon in the pp→ppπ+π− Reaction?

Author: A. Magiera, Stanisław Kistryn, O. Khreptak, H. Clement, A. Bondar, B. Shwartz, J. Stepaniak, Lena Heijkenskjöld, D. Prasuhn, K. Lalwani, H. Ohm, D. Lersch, W. Erven, T. Johansson, Jozef Zlomanczuk, H. P. Morsch, G. Sterzenbach, B. Lorentz, Ralf Engels, Pawel Marciniewski, B. Kłos, Wiktor Parol, A. Khoukaz, D. Pszczel, K. Föhl, H. Ströher, Izabela Ciepał, F. S. Bergmann, K. Pysz, P. Fedorets, W. Augustyniak, J. Ritman, V. Serdyuk, S. Sawant, Frank Goldenbaum, Jerzy Smyrski, Aleksandra Wrońska, E. Perez del Rio, Hans Stockhorst, Magnus Wolke, V. Hejny, M. Bashkanov, I. Schätti-Ozerianska, T. Sefzick, S. Schadmand, Akira Yamamoto, A. Kupść, A. Trzcinski, Marcin Zieliński, Rolf Stassen, A. Erven, Di. Kirillov, P. Żuprański, B. Kamys, Markus Büscher, W. Eyrich, Günter Kemmerling, P. Wüstner, N. Hüsken, Hans Calén, P. Adlarson, K. Grigoryev, Kjell Fransson, Magdalena Skurzok, M. Żurek, Paweł Moskal, L. Jarczyk, M. Berłowski, Wojciech Krzemien, R. Maier, A. Goswami, K. Demmich, T. Skorodko, B. Mariański, J. Zabierowski, Antoni Szczurek, Zbigniew Rudy, Eryk Czerwiński, Harald Kleines, V. Sopov, W. Bardan, Oleksandr Rundel, E. Stephan, P. Kulessa, N.M. Piskunov, and Ankhi Roy
Subjects: Nuclear physics, Physics, Cross section (physics), Pion, Meson, 010308 nuclear & particles physics, Excited state, 0103 physical sciences, General Physics and Astronomy, 010306 general physics, 01 natural sciences, Resonance (particle physics), Energy (signal processing)
Abstract: Exclusive measurements of the quasifree pp→ppπ^{+}π^{-} reaction have been carried out at WASA@COSY by means of pd collisions at T_{p}=1.2 GeV. Total and differential cross sections have been extracted covering the energy region T_{p}=1.08-1.36 GeV, which is the region of N^{*}(1440) and Δ(1232)Δ(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor ΔN dibaryon resonance with I(J^{P})=2(1^{+}) produced associatedly with a pion is able to overcome these deficiencies.
Published: 2018

29. Importance of -wave Contributions in the Charge Symmetry Breaking Reaction

Author: D. Lersch, O. Khreptak, M. Bashkanov, K. Grigoryev, A. Erven, K. Sitterberg, K. Föhl, Izabela Ciepał, H. Ströher, Oleksandr Rundel, A. Magiera, V. Sopov, T. Johansson, B. Kłos, Jozef Zlomanczuk, A. Trzcinski, L. Jarczyk, B.A. Shwartz, A. Khoukaz, Hans Stockhorst, G. Khatri, E. Stephan, Rolf Stassen, G. Sterzenbach, Marcin Zieliński, S. Sawant, B. Lorentz, N.M. Piskunov, A. Kuzmin, A. Goswami, J. Zabierowski, K. Demmich, C.-O. Gullström, Markus Büscher, Antoni Szczurek, W. Bardan, S. Schadmand, D. Pszczel, Rudolf Maier, Ankhi Roy, P. Kulessa, P. Adlarson, J. Stepaniak, W. Erven, Wiktor Parol, Zbigniew Rudy, I. Schätti-Ozerianska, K. Lalwani, Magdalena Skurzok, Eryk Czerwiński, B. Mariański, Aleksandra Wrońska, K. Pysz, P. Fedorets, Harald Kleines, E. Perez del Rio, Hans Calén, B. Kamys, P. Wüstner, F. S. Bergmann, Wojciech Krzemien, Magnus Wolke, M. Berłowski, H. P. Morsch, H. Ohm, Kjell Fransson, H. Clement, Frank Goldenbaum, T. Skorodko, T. Sefzick, Pawel Marciniewski, P. Żuprański, M. Żurek, J. Ritman, V. Serdyuk, Jerzy Smyrski, Ralf Engels, Günter Kemmerling, W. Eyrich, N. Hüsken, Christoph Hanhart, Stanisław Kistryn, Lena Heijkenskjöld, D. Prasuhn, A. Pyszniak, W. Augustyniak, Paweł Moskal, V. Hejny, Akira Yamamoto, A. Kupść, Di. Kirillov, and A.E. Bondar
Subjects: Physics, Quark, Nuclear and High Energy Physics, Meson, 010308 nuclear & particles physics, Spontaneous symmetry breaking, Hadron, Charge (physics), 01 natural sciences, Nuclear physics, Pion, 0103 physical sciences, Isobar, Symmetry breaking, Atomic physics, 010306 general physics
Abstract: This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd→4Heπ0 using the WASA-at-COSY detector setup at an excess energy of Q=60MeV. The determined differential cross section can be parametrized as dσ/dΩ=a+bcos2⁡θ⁎, where θ⁎ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a=(1.55±0.46(stat)+0.32−0.8(syst))pb/sr and b=(13.1±2.1(stat)−2.7+1.0(syst))pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Δ isobar to the dd→4Heπ0 reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.
Published: 2018

30. Status of the Dibaryon Resonance $d^*(2380)$

Author: T. Skorodko, H. Clement, and M. Bashkanov
Subjects: Physics, Particle physics, Deuterium, Scattering, Isoscalar, Nuclear Theory, Hexaquark, High Energy Physics::Experiment, Nuclear Experiment
Abstract: The dibaryon resonance $d^*(2380)$ with $I(J^P) = 0(3^+)$ --- first observed in the double-pionic fusion to the deuteron --- has meanwhile been detected in all relevant two-pion production channels by incident neutron-proton collisions. In addition, its resonance pole has been revealed in neutron-proton scattering. Theoretical calculations describe this state either as a compact hexaquark system or a dilute molecular-like object. Whereas the $d^*$ decay into two-pion channels does not discriminate between these two scenarios, the decay into single-pion channels is very discriminatory. In the hexaquark case this decay is heavily suppressed with a branching of less than 1$\%$. In the molecular-like case a branching of as much as 18$\%$ is expected. In order to clarify this situation we have measured the isoscalar single-pion production in the energy region of d*(2380). As a result we find no evidence for such a decay with an upper limit of smaller than 9$\%$. This is in support of the hexaquark interpretation -- at least as the dominant configuration, possibly surrounded by a cloud of molecular-like configurations. Other dibaryon candidates are currently under investigation.
Published: 2018

31. Total and differential cross sections of η -production in proton–deuteron fusion for excess energies between Q η = 13 MeV and Q η = 81 MeV

Author: B.A. Shwartz, A. Khoukaz, M. Bashkanov, A. Erven, K. Sitterberg, Hans Calén, K. Grigoryev, Stanisław Kistryn, D. Pszczel, P. Adlarson, Kjell Fransson, K. Pysz, P. Fedorets, D. Lersch, A. Khreptak, S. Schadmand, H. Clement, Ankhi Roy, A. Pyszniak, W. Augustyniak, Günter Kemmerling, H. Ströher, K. Lalwani, I. Schätti-Ozerianska, L. Jarczyk, Zbigniew Rudy, Lena Heijkenskjöld, D. Prasuhn, P. Kulessa, C.-O. Gullström, Frank Goldenbaum, T. Johansson, F. S. Bergmann, Eryk Czerwiński, W. Eyrich, B. Kłos, W. Erven, Magnus Wolke, Wiktor Parol, Markus Büscher, J. Stepaniak, Pawel Marciniewski, N. Hüsken, Harald Kleines, C. Wilkin, Izabela Ciepał, S. Sawant, A. Kuzmin, Jozef Zlomanczuk, J. Zabierowski, H. P. Morsch, G. Sterzenbach, B. Lorentz, P. Żuprański, A. Trzcinski, Hans Stockhorst, Di. Kirillov, Antoni Szczurek, G. Khatri, A. Magiera, V. Serdyuk, Paweł Moskal, James Ritman, Ralf Engels, Rolf Stassen, A. Goswami, Jerzy Smyrski, B. Kamys, K. Demmich, Wojciech Krzemien, P. Wüstner, Oleksandr Rundel, N.M. Piskunov, A.E. Bondar, R. Maier, V. Hejny, Akira Yamamoto, A. Kupść, Aleksandra Wrońska, E. Perez del Rio, E. Stephan, K. Föhl, Magdalena Skurzok, H. Ohm, V. Sopov, W. Bardan, B. Mariański, M. Berłowski, T. Skorodko, Marcin Zieliński, T. Sefzick, and M. Żurek
Subjects: Nuclear and High Energy Physics, eta meson, Proton, Meson, Hadron, Nuclear Theory, Elementary particle, η meson, 7. Clean energy, 01 natural sciences, Nuclear physics, Subatomär fysik, proton–deuteron interactions, Astronomi, astrofysik och kosmologi, 0103 physical sciences, протон-дейтронные взаимодействия, Subatomic Physics, Astronomy, Astrophysics and Cosmology, ddc:530, 010306 general physics, Nuclear Experiment, Boson, Physics, 010308 nuclear & particles physics, Eta meson, Meson production, lcsh:QC1-999, Deuterium, meson production, Proton-deuteron interactions, \eta meson, мезоны, Physics::Accelerator Physics, High Energy Physics::Experiment, ηмезоны, Beam (structure), lcsh:Physics
Abstract: New data on both total and differential cross sections of the production of η mesons in proton–deuteron fusion to He3η in the excess energy region 13.6MeV≤Qη≤80.9MeV are presented. These data have been obtained with the WASA-at-COSY detector setup located at the Forschungszentrum Jülich, using a proton beam at 15 different beam momenta between pp=1.60GeV/c and pp=1.74GeV/c. While significant structure of the total cross section is observed in the energy region 20MeV≲Qη≲60MeV, a previously reported sharp variation around Qη≈50MeV cannot be confirmed. Angular distributions show the typical forward-peaking that was noted earlier. For the first time, it is possible to study the development of these angular distributions with rising excess energy over a wide interval.
Published: 2018

32. Charge symmetry breaking in dd→He4π0 with WASA-at-COSY

Author: Izabela Ciepał, H. Bhatt, Hans Stockhorst, V. Sopov, D. Lersch, Marcin Zieliński, Rolf Stassen, A. Pricking, Bo Höistad, Jozef Zlomanczuk, A.S. Kuzmin, C.-O. Gullström, Markus Büscher, C. F. Redmer, A. Goswami, E. Doroshkevich, B. Mariański, Aleksandra Wrońska, E. Perez del Rio, P. Goslawski, K. Demmich, P. Wurm, H. Clement, K. Lalwani, Stanisław Kistryn, W. Eyrich, D. Coderre, R. Varma, M. Berłowski, A. Pyszniak, W. Augustyniak, K. Föhl, I. Ozerianska, W. Bardan, L. Yurev, P. Podkopał, S. Sawant, Lena Heijkenskjöld, F. S. Bergmann, A. Zink, Zbigniew Rudy, F. Hauenstein, D. Prasuhn, Paweł Moskal, R. Siudak, Magnus Wolke, T. Skorodko, N. Hüsken, Ankhi Roy, R. Maier, J. Stepaniak, W. Erven, P. Kulessa, Eryk Czerwiński, V. Hejny, S. Schadmand, Akira Yamamoto, A. Kupść, B. Kamys, T. Sefzick, Harald Kleines, P. Wüstner, K. Grigoryev, P. Adlarson, Christoph Hanhart, H. Ströher, E. Stephan, N.M. Piskunov, T. Johansson, M. Żurek, L. Jarczyk, B. Kłos, Wojciech Krzemien, K. Pysz, P. Fedorets, Ferdous Khan, Pawel Marciniewski, H. Ohm, V. Serdyuk, B.A. Shwartz, A. Khoukaz, H. P. Morsch, Jerzy Smyrski, M. Mikirtychiants, Magdalena Skurzok, M. Bashkanov, Günter Kemmerling, A. Trzciński, A. Erven, G. Sterzenbach, B. Lorentz, D. Pszczel, Ralf Engels, A. Täschner, A. Magiera, James Ritman, Frank Goldenbaum, P. Żuprański, A.E. Bondar, Hans Calén, Di. Kirillov, J. Zabierowski, Kjell Fransson, and Antoni Szczurek
Subjects: Physics, Quark, Nuclear and High Energy Physics, Particle physics, Chiral perturbation theory, 010308 nuclear & particles physics, Nuclear Theory, Observable, Charge (physics), 01 natural sciences, Nuclear physics, 0103 physical sciences, Sum rule in quantum mechanics, Symmetry breaking, Nuclear Experiment, 010306 general physics
Abstract: Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are cu ...
Published: 2014

33. Spin dependence of {\eta} meson production in proton-proton collisions close to threshold

Author: M. Bashkanov, Günter Kemmerling, A. Erven, I. Schätti-Ozerianska, K. Sitterberg, G. Sterzenbach, W. Eyrich, A. Magiera, B. Lorentz, H. P. Morsch, O. Khreptak, Ralf Engels, N. Hüsken, Paweł Moskal, Zbigniew Rudy, Marcin Zieliński, Eryk Czerwiński, C.-O. Gullström, Markus Büscher, Harald Kleines, Ankhi Roy, W. Bardan, Aleksandra Wrońska, Hans Calén, E. Perez del Rio, T. Sefzick, Stanisław Kistryn, J. Zabierowski, K. Pysz, V. Hejny, Akira Yamamoto, Kjell Fransson, Lena Heijkenskjöld, D. Prasuhn, Antoni Szczurek, A. Khoukaz, Magdalena Skurzok, B. Mariański, K. Grigoryev, Jozef Zlomanczuk, Wojciech Krzemien, V. Sopov, Andrzej Kupsc, Patrik Adlarson, Frank Goldenbaum, Pawel Marciniewski, Damian Pszczel, B. Shwartz, J. Stepaniak, P. Zupranski, D. Lersch, J. Ritman, A. Trzcinski, G. Khatri, P. Fedorets, W. Augustyniak, Tord Johansson, L. Jarczyk, W. Erven, V. Serdyuk, Steven D. Bass, H. Ohm, H. Clement, M. Berłowski, K. Föhl, K. Lalwani, A. Bondar, H. Stroeher, Maria Zurek, Jerzy Smyrski, B. Kamys, P. Wüstner, B. Kłos, T. Skorodko, S. Schadmand, K. Demmich, A. Pyszniak, S. Sawant, Di. Kirillov, A. Kuzmin, F. S. Bergmann, Magnus Wolke, Izabela Ciepał, A. Goswami, Hans Stockhorst, Rolf Stassen, Rudolf Maier, P. Kulessa, Wiktor Parol, Oleksandr Rundel, E. Stephan, and N.M. Piskunov
Subjects: Nuclear Theory, General Physics and Astronomy, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, 0103 physical sciences, ddc:530, FACILITY, NEAR-THRESHOLD, 010306 general physics, NUCLEON, Nuclear Experiment, Nuclear theory, Physics, QUASI-FREE, 010308 nuclear & particles physics, Eta meson, Detector, COSY, Polarization (waves), Near threshold, High Energy Physics - Phenomenology, Physics::Accelerator Physics, Axial symmetry, Nucleon
Abstract: Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high degree of the polarized proton beam of COSY, the reaction pp{\to} pp{\eta} has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the precision improved by more than one order of magnitude with respect to previous results allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q = 15 MeV signaling s wave production with no evidence for higher partial waves. At Q = 72 MeV the data reveals strong interference of P s and P p partial waves and cancellation of (P p) and Ss*Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the {\eta} meson., Comment: Accepted for publication in Phys. Rev. Lett
Published: 2017

34. Determination of the spin tripletpΛscattering length from the final state interaction in thep⃗p→pK+Λreaction

Author: K. Ehrhardt, M. Mertens, A. Gillitzer, D. Grzonka, W. Schroeder, J. Ritman, W. Eyrich, W. Gast, Paweł Moskal, Paweł Klaja, C. Hanhart, M. Krapp, E. Doroshkevich, K. Kilian, L. Kober, E. Borodina, P. Wüstner, T. Sefzick, F. Hauenstein, R. Dzhygadlo, S. Jowzaee, Johann Haidenbauer, E. Roderburg, M. Röder, P. Wintz, and H. Clement
Subjects: Physics, Particle physics, Proton, 010308 nuclear & particles physics, Scattering length, Time model, State (functional analysis), Lambda, 01 natural sciences, 0103 physical sciences, High Energy Physics::Experiment, Atomic physics, Nuclear Experiment, 010306 general physics, Spin-½
Abstract: The $\stackrel{P\vec}{p}p\ensuremath{\rightarrow}p{K}^{+}\mathrm{\ensuremath{\Lambda}}$ reaction has been measured with the COSY-TOF detector at a beam momentum of $2.7\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/c$. The polarized proton beam enables the measurement of the beam analyzing power by the asymmetry of the produced kaon $({A}_{N}^{K})$. This observable allows the $p\mathrm{\ensuremath{\Lambda}}$ spin triplet scattering length to be extracted for the first time model independently from the final state interaction in the reaction. The obtained value is ${a}_{t}=(\ensuremath{-}2.{55}_{\ensuremath{-}1.39}^{+0.72}{}_{\mathrm{stat}.}\ifmmode\pm\else\textpm\fi{}0.{6}_{\mathrm{syst}.}\ifmmode\pm\else\textpm\fi{}0.{3}_{\mathrm{theo}.})\mathrm{fm}$. This value is compatible with theoretical predictions and results from model-dependent analyses.
Published: 2017

35. Recent results from WASA-at-COSY

Author: Magdalena Skurzok, Paweł Moskal, and H. Clement
Subjects: Physics
Published: 2017

36. Observation of the ABC effect and final-state isospin

Author: T. Yu Skorodko, G. J. Wagner, M. Bashkanov, E. Doroshkevich, A. Pricking, E. Perez del Rio, and H. Clement
Subjects: Physics, Nuclear and High Energy Physics, Particle physics, Isovector, Dalitz plot, Isoscalar, isovector channel, State (functional analysis), Atomic and Molecular Physics, and Optics, atomic nucleus, Nuclear physics, Isospin, Atomic nucleus, exclusive measurement, Nuclear fusion, Pi interaction, total cross section
Abstract: Despite the number of inclusive measurements of the pionic fusion reactions, the nature of the ABC effect discovered in 1960 was not completely established. Exclusive measurements of the doublepion-production reactions leading to either fused d, 3He and 4He nuclear final states or pp pairs are analyzed. A significant ABC effect—enhancement in the region of low ππ mass—is found only in the isoscalar ππ channel while in the isovector channels it is small or absent. For the reaction with isovector pp final state an ABC effect was not observed even at the special kinematic conditions to reproduce a quasi-bound two-proton state. The total cross sections for the d and 4He fusion reactions show similar resonance-like energy dependence.
Published: 2014

37. Measurements of branching ratios for η decays into charged particles

Author: A. Kupść, Oleksandr Rundel, Akira Yamamoto, T. Johansson, B. Kłos, K. Fransson, E. Stephan, K. Grigoryev, B. Kamys, R. Engels, P. Wüstner, K. Pysz, Ferdous Khan, S. Sawant, Zbigniew Rudy, L. Jarczyk, V. Hejny, K. Föhl, Jozef Zlomanczuk, C.-O. Gullström, Markus Büscher, P. Fedorets, Ankhi Roy, Paweł Moskal, D. Lersch, A. Trzcinski, T. Sefzick, Marcin Zieliński, Stanisław Kistryn, A.E. Bondar, B. Shwartz, J. Stepaniak, A. Magiera, Eryk Czerwiński, R. Varma, K. Demmich, Lena Heijkenskjöld, D. Prasuhn, I. Ozerianska, Harald Kleines, G. Khatri, P. Kulessa, J. Zabierowski, Pawel Marciniewski, M. Berłowski, H. P. Morsch, W. Eyrich, Himani Bhatt, Antoni Szczurek, T. Skorodko, F. S. Bergmann, Magnus Wolke, Aleksandra Wrońska, E. Perez del Rio, A. Kuzmin, J. Ritman, P. Adlarson, N. Hüsken, V. Serdyuk, A. Pyszniak, W. Augustyniak, Jerzy Smyrski, K. Lalwani, M. Żurek, H. Ohm, H. Clement, P. Wurm, N.M. Piskunov, S. Schadmand, B. Mariański, Wojciech Krzemien, W. Erven, R. Siudak, D. Coderre, W. Bardan, M. Mikirtychiants, Magdalena Skurzok, Ulrich Wiedner, V. Sopov, D. Pszczel, R. Maier, H. Ströher, Di. Kirillov, G. Sterzenbach, B. Lorentz, A. Täschner, Günter Kemmerling, Frank Goldenbaum, P. Żuprański, Hans Calén, M. Bashkanov, A. Erven, K. Sitterberg, A. Khoukaz, Izabela Ciepał, A. Goswami, Hans Stockhorst, Rolf Stassen, and A. Zink
Subjects: Energy loss, Particle physics, Meson, Dalitz plot, Branching (polymer chemistry), 01 natural sciences, Subatomär fysik, Conversion Decays, Subatomic Physics, 0103 physical sciences, ddc:530, Gamma, Transition Form-Factors, Nuclear Experiment, 010306 general physics, Na60, Physics, Omega, 010308 nuclear & particles physics, Branching fraction, High Energy Physics::Phenomenology, Detector, Mu(+)Mu(-)Gamma, Charged particle, Crystallography, High Energy Physics::Experiment
Abstract: The WASA-at-COSY experiment has collected $3\ifmmode\times\else\texttimes\fi{}{10}^{7}$ events with $\ensuremath{\eta}$ mesons produced via the reaction $pd\ensuremath{\rightarrow}^{3}\mathrm{He}\phantom{\rule{0.16em}{0ex}}\ensuremath{\eta}$ at $\mathrm{T}=1.0\phantom{\rule{4pt}{0ex}}\mathrm{GeV}$. Using this data set, we evaluate the branching ratios of the decays $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$, $\ensuremath{\eta}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}\ensuremath{\gamma}$, $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{e}^{\ensuremath{-}}$, and $\ensuremath{\eta}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{e}^{+}{e}^{\ensuremath{-}}$. The branching ratios are normalized to the $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ decay. In addition an upper limit on a $CP$-violating asymmetry in $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{e}^{\ensuremath{-}}$ is extracted.
Published: 2016

38. Search for a dark photon in the π0→e+e−γ decay

Author: M. Mikirtychiants, Magdalena Skurzok, C. F. Redmer, Bo Höistad, G. J. Wagner, Jozef Zlomanczuk, A. Magiera, P. Goslawski, T. Sefzick, W. Eyrich, James Ritman, B. Mariański, C.-O. Gullström, Markus Büscher, H. Clement, Zbigniew Rudy, R. Siudak, Eryk Czerwiński, A. Trzcinski, Harald Kleines, Aleksandra Wrońska, Ulf-G. Meißner, A. Bondar, E. Perez del Rio, N. Shah, K. Pysz, P. Fedorets, Ferdous Khan, W. Zipper, P. Adlarson, W. Bardan, J. Zabierowski, K. Lalwani, Ankhi Roy, M. Hodana, Antoni Szczurek, P. Wurm, H. P. Morsch, H. Ohm, R. Varma, D. Pszczel, M. Żurek, Izabela Ciepał, T. Johansson, I. Ozerianska, V. Hejny, K. Föhl, B. Kłos, M. Siemaszko, Hans Stockhorst, V. Sopov, E. Stephan, H. Ströher, Marcin Zieliński, Frank Goldenbaum, S. Sawant, Pawel Marciniewski, F. Hauenstein, P. Podkopał, Rolf Stassen, K. Grigoryev, E. Doroshkevich, B. Shwartz, J. Stepaniak, Stanisław Kistryn, P. Pluciński, Alexander Schmidt, M. Krapp, P. Żuprański, F. Hinterberger, Hans Calén, R. Maier, Lena Heijkenskjöld, A. Jany, D. Prasuhn, Wojciech Krzemien, L. Li, Kjell Fransson, W. Wȩglorz, T. Tolba, Akira Yamamoto, A. Kupść, M. Berłowski, W. Erven, L. Jarczyk, Andreas Wirzba, A. Pricking, T. Skorodko, K. Demmich, V. Serdyuk, Di. Kirillov, G. Sterzenbach, B. Lorentz, Jerzy Smyrski, M. Bashkanov, F. S. Bergmann, Ralf Engels, Magnus Wolke, Paweł Moskal, Günter Kemmerling, S. Schadmand, B. Kamys, A. Pyszniak, W. Augustyniak, P. Wüstner, A. Goswami, A. Khoukaz, Himani Bhatt, Basanta Kumar Nandi, N.M. Piskunov, Benedykt R. Jany, P. Kulessa, A. Kuzmin, J. Klaja, D. Coderre, and D. Lersch
Subjects: Physics, Nuclear and High Energy Physics, Muon, Anomalous magnetic dipole moment, Magnetic moment, 010308 nuclear & particles physics, Elementary particle, 01 natural sciences, 7. Clean energy, Dark photon, Nuclear physics, Massless particle, Particle decay, 0103 physical sciences, 010306 general physics, Lepton
Abstract: The presently world largest data sample for π 0 → γ e + e − decays studies containing nearly 5 × 10 5 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the π 0 → γ U → γ e + e − decay from the p p → p p π 0 reaction was carried out. An upper limit on the square of the U − γ mixing strength parameter ϵ 2 of 5 × 10 − 6 at 90% CL was obtained for the mass range 20 MeV M U 100 MeV . This result together with other recent experimental limits significantly reduces the M U vs. ϵ 2 parameter space which could explain the presently seen deviation between the Standard Model prediction and the direct measurement of the anomalous magnetic moment of the muon.
Published: 2013

39. On the History of Dibaryons and their Final Observation

Author: H. Clement
Subjects: Physics, Nuclear and High Energy Physics, Particle physics, 010308 nuclear & particles physics, High Energy Physics::Lattice, High Energy Physics::Phenomenology, Nuclear Theory, FOS: Physical sciences, Object (computer science), 01 natural sciences, Resonance (particle physics), High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), 0103 physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment
Abstract: A review is given about the long-standing search for dibaryons, i.e. six-quark objects, from the early days until present, when the first dibaryon resonance has been established, which has the potential of constituting a compact six-quark object.
Published: 2016

40. Measurement of polarization observables of the associated strangeness production in proton proton interactions

Author: P. Wintz, F. Hauenstein, D. Grzonka, W. Eyrich, K. Kilian, P. Wüstner, Paweł Moskal, R. Dzhygadlo, T. Sefzick, L. Kober, W. Schroeder, M. Röder, H. Clement, M. Krapp, K. Ehrhardt, S. Jowzaee, E. Roderburg, E. Doroshkevich, P. Klaja, M. Mertens, A. Gillitzer, J. Ritman, Jerzy Smyrski, E. Borodina, and W. Gast
Subjects: Physics, Nuclear and High Energy Physics, 010308 nuclear & particles physics, Partial wave analysis, Polarization observables, Hadron, FOS: Physical sciences, Strangeness production, Physik (inkl. Astronomie), Polarization (waves), 01 natural sciences, Nuclear physics, 0103 physical sciences, Spin transfer, Nuclear fusion, ddc:530, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment, Excess energy
Abstract: The Lambda polarization, the analyzing power, and the Lambda spin transfer coefficient of the reaction pp -> p K+ Lambda were measured at beam momenta of 2.70 GeV/c and 2.95 GeV/c, corresponding to excess energies of 122 MeV and 204 MeV. While the analyzing power and the spin transfer coefficient do not change significantly with the excess energy, the Lambda polarization varies strongly and changes its sign. As this is the first measurement of polarization observables below an excess energy of 200 MeV, the change of the sign of the Lambda polarization was not observed before. The high statistics of the data (~200 k events for each momentum) enables detailed studies of the dependence of the Lambda polarization and the analyzing power on the center of mass momentum of the particles. The results of the spin transfer coefficient are in qualitative agreement with the DISTO experiment. The Lambda polarization data of 2.95 GeV/c are only conform with the DISTO experiment, while both the 2.70 GeV/c and 2.95 GeV/c data differ strongly from all previous measurements, whether exclusive or inclusive., Revised version as accepted for publication in EPJA
Published: 2016

41. High-precision measurement of the associated strangeness production in proton-proton interactions

Author: T. Sefzick, R. Dzhygadlo, E. Borodina, F. Hauenstein, M. Krapp, L. Kober, E. Roderburg, P. Wintz, S. Jowzaee, M. Röder, James Ritman, K. Ehrhardt, W. Eyrich, Paweł Moskal, E. Doroshkevich, P. Klaja, H. Clement, M. Mertens, W. Schroeder, Jerzy Smyrski, A. Gillitzer, P. Wüstner, D. Grzonka, K. Kilian, and W. Gast
Subjects: Physics, Nuclear and High Energy Physics, Particle physics, 010308 nuclear & particles physics, Partial wave analysis, Hadron, Dalitz plot, Strangeness production, Physik (inkl. Astronomie), Lambda, 01 natural sciences, Helicity, Nuclear physics, 0103 physical sciences, Invariant mass, ddc:530, 010306 general physics, Wave function, Nuclear Experiment
Abstract: A new high-precision measurement of the reaction $pp\rightarrow pK^{+}\Lambda$ at a beam momentum of 2.95 GeV/c with more than 200 000 analyzed events allows a detailed analysis of differential observables and their inter-dependencies. Correlations of the angular distributions with momenta are examined. The invariant mass distributions are compared for different regions in the Dalitz plots. The cusp structure at the $N\Sigma$ threshold is described with the Flatte formalism and its variation in the Dalitz plot is analyzed.
Published: 2016

42. Two-pion production in nucleon–nucleon collisions—Back to dibaryons?

Author: H. Clement
Subjects: Physics, Nuclear and High Energy Physics, Particle physics, Isovector, Isoscalar, Nuclear Theory, Nuclear physics, Pion, Intermediate state, Nuclear fusion, Invariant mass, Nuclear Experiment, Nucleon, Excitation
Abstract: The two-pion production in nucleon–nucleon collisions has been investigated systematically by exclusive and kinematically complete measurements at CELSIUS/WASA and more recently at COSY-TOF and particularly WASA@COSY. The data for all p p -induced isovector production channels in the energy range from threshold up to T p = 1.4 GeV can be well understood by t -channel Roper, Δ Δ and possibly Δ ( 1600 ) excitation. In contrast to that the purely isoscalar reaction channel p n → d π 0 π 0 exhibits a narrow resonance-like structure with m = 2.37 GeV and Γ = 70 MeV in the total cross section, which is correlated with an intriguing low-mass enhancement in the π π invariant mass spectrum (ABC effect) as well as with the formation of a Δ Δ system in the intermediate state. From the angular distributions the spin and parity of this structure have been derived resulting in I ( J P ) = 0 ( 3 + ) . The consequences of the resonance hypothesis for other reaction channels are discussed. The fact that also the double-pionic fusion reactions to 3He and 4He exhibit a corresponding resonance-like structure in the total cross section correlated with the ABC effect suggests that the underlying conjectured p n resonance is obviously robust enough to survive in nuclei.
Published: 2012

43. Exclusive measurement of the η→π+π−γ decay

Author: Paweł Moskal, B. Lorentz, A. Magiera, Ulf-G. Meißner, M. Berłowski, H. P. Morsch, C. Adolph, C.-O. Gullström, Markus Büscher, B. Kamys, Benedykt R. Jany, A. Winnemöller, Jozef Zlomanczuk, James Ritman, Joanna Klaja, M. Mikirtychiants, D. Coderre, P. Wüstner, P. Goslawski, Magdalena Skurzok, R. Maier, G. J. Wagner, S. Schadmand, H. Clement, P. Fedorets, G. Sterzenbach, Günter Kemmerling, Bo Höistad, Paweł Podkopał, W. Eyrich, F. Stollenwerk, J. Heimlich, L. Jarczyk, A. Trzciński, T. Skorodko, A. Schmidt, Aleksandra Wrońska, A. Povtoreyko, E. Perez del Rio, X. Yuan, Tomasz Bednarski, Annika Passfeld, Zbigniew Rudy, H. Bhatt, W. Erven, Basanta Kumar Nandi, T. Sefzick, Stanisław Kistryn, J. Stepaniak, R. Engels, A. Pricking, D. Prasuhn, K. Föhl, R. Varma, P. Wurm, Andreas Wirzba, P. Pluciński, Eryk Czerwiński, K. T Brinkmann, K. Grigoryev, C. Zheng, Szymon Niedźwiecki, Harald Kleines, P. Vlasov, M. Hodana, W. Zipper, Lena Heijkenskjöld, W. Bardan, C. F. Redmer, P. Adlarson, P. Kulessa, T. Tolba, V. Serdyuk, R. Siudak, Hans Stockhorst, L. Yurev, Pawel Marciniewski, A. Täschner, H. Ohm, K. Pysz, T. Rausmann, Rolf Stassen, Christoph Hanhart, E. Doroshkevich, J. Zabierowski, F. Hinterberger, A. Jany, M. Siemaszko, Antoni Szczurek, Wojciech Krzemien, V. Sopov, F. S. Bergmann, Magnus Wolke, F. Kren, Jerzy Smyrski, Hans Calén, Kjell Fransson, T. Johansson, Frank Goldenbaum, B. Kłos, W. Węglorz, A. Pyszniak, W. Augustyniak, V. Hejny, S. Sawant, A. Kupść, Carla Terschlüsen, M. Bashkanov, P. Żuprański, Stefan Leupold, K. Lalwani, Y. Petukhov, A. Khoukaz, N.M. Piskunov, Marek Jacewicz, C. Pauly, N. Shah, Marcin Zieliński, H. Ströher, Ankhi Roy, O. Khakimova, B. Mariański, and T. Petri
Subjects: Physics, Nuclear and High Energy Physics, Proton, Meson, 010308 nuclear & particles physics, Nuclear Theory, Eta meson, Hadron, 01 natural sciences, 7. Clean energy, Nuclear physics, Pion, Helium-3, 0103 physical sciences, Physics::Accelerator Physics, High Energy Physics::Experiment, Nuclear Experiment, 010306 general physics, Isotopes of helium, Dimensionless quantity
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 be ...
Published: 2012

44. π0π0 Production in proton–proton collisions at Tp=1.4 GeV

Author: Aleksandra Wrońska, E. Perez del Rio, A. Povtoreyko, P. Wurm, G. J. Wagner, A. Taeschner, L. Yurev, P. Zupranski, X. Yuan, Pawel Plucinski, Ankhi Roy, W. Eyrich, P. Kulessa, C. Zheng, C. F. Redmer, B. Kamys, Stanisław Kistryn, Annika Passfeld, W. Węglorz, A. Khoukaz, M. Hodana, M. Berłowski, A. Magiera, C. Adolph, P. Podkopał, Ulrich Wiedner, W. Augustyniak, A. Pricking, F. Goldenbaum, Lena Heijkenskjöld, James Ritman, Jozef Zlomanczuk, Hans Stockhorst, Basanta Kumar Nandi, D. Prasuhn, Marek Jacewicz, Ralf Engels, H. Bhatt, H. P. Morsch, N.M. Piskunov, C. Pauly, R. Maier, Bo Höistad, M. Buescher, F. Hinterberger, T. Skorodko, Benedykt R. Jany, A. Schmidt, K. Lalwani, W. Erven, T. Sefzick, M. Bashkanov, Paweł Moskal, A. Winnemoeller, S. Schadmand, P. Vlasov, W. Zipper, Zbigniew Rudy, Eryk Czerwiński, G. Kemmerling, Y. Petukhov, T. Tolba, R. Stassen, V. Serdyuk, Pawel Marciniewski, V. Hejny, Jerzy Smyrski, P. Goslawski, B. Kłos, H. Clement, S. Sawant, K. Foehl, C.-O. Gullström, N. Shah, Andrzej Kupsc, L. Jarczyk, J. Stepaniak, H. Kleines, G. Sterzenbach, J. Heimlich, Bernd Lorentz, E. Doroshkevich, K. Pysz, F. S. Bergmann, Magnus Wolke, Hans Calén, A. Jany, A. Trzciński, Tomasz Bednarski, R. Varma, K. Grigoryev, M. Siemaszko, Kjell Fransson, P. Fedorets, J. Klaja, D. Coderre, V. Sopov, F. Kren, S. Niedzwiecki, Wojciech Krzemien, H. Stroeher, Marcin Zieliński, J. Zabierowski, Antoni Szczurek, M. Mikirtychiants, Magdalena Skurzok, T. Rausmann, O. Khakimova, B. Mariański, P. Wuestner, Patrik Adlarson, Tord Johansson, H. Ohm, Michał Janusz, and K. T Brinkmann
Subjects: Physics, Baryon, Nuclear physics, Nuclear and High Energy Physics, Particle physics, Pion, Meson, Proton, Hadron, Pi, Elementary particle, Nucleon
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(normaliz ...
Published: 2012

45. ΔΔ excitation in proton–proton induced π0π0 production

Author: Wolfgang Scobel, Bo Höistad, S. Keleta, G. J. Wagner, S. Kullander, H. Petrén, Akira Yamamoto, E. Jiganov, H. Clement, O. Khakimova, G. Ivanov, T. Skorodko, C. Ekström, Hans Calén, Leif Gustafsson, Marek Jacewicz, Jozef Zlomanczuk, C. Pauly, Karin Schönning, I. Koch, E. Doroshkevich, M. Bashkanov, J. Zabierowski, R. Meier, Pawel Marciniewski, V. Tikhomirov, L. Demiroers, Y. Petukhov, K. Fransson, A. Kupść, T. Johansson, A. Povtorejko, P. Thörngren-Engblom, F. Kren, Magnus Wolke, D. Bogoslawsky, B. Morosov, B. Shwartz, J. Stepaniak, and R. J. M. Y. Ruber
Subjects: Nuclear physics, Delta, Physics, Nuclear and High Energy Physics, Proton, Degree Celsius, Pi, Atomic physics, Excitation
Abstract: Exclusive measurements of the pp -> 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 obt ...
Published: 2011

46. Cross sections of the pp→K+Σ+n reaction close to threshold

Author: J. Urban, B. J. Roy, G. J. Wagner, G. Martinska, H. Clement, E. Dorochkevitch, A. Chatterjee, A. Sibirtsev, P. Hawranek, D. Kolev, P. von Rossen, Di. Kirillov, M. Lesiak, R. Jahn, A. Budzanowski, D. Protic, S. Kliczewski, N.M. Piskunov, R. Joosten, A. Magiera, R. Siudak, M. Kravcikova, F. Hinterberger, K. Kilian, I.M. Sitnik, K. Ulbrich, Da. Kirillov, Hartmut Machner, J. Ritman, and R. Tsenov
Subjects: Physics, Nuclear and High Energy Physics, Meson, Nuclear Theory, Hadron, Hyperon, Elementary particle, Sigma baryon, Nuclear physics, Baryon, Mass spectrum, Invariant mass, Atomic physics, Nuclear Experiment
Abstract: We have measured inclusive data on K + -meson production in pp collisions at COSY Julich close to the hyperon production threshold and determined the hyperon–nucleon invariant mass spectra. The spectra were decomposed into three parts: Λp, Σ 0 p and Σ + n . The cross section for the Σ + n channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.
Published: 2010

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

Author: Andrzej Kupsc, H. Clement, P.-E. Tegnér, R. Shafigullin, G. J. Wagner, V. Sopov, L. Demiroers, F. Kren, C. Pauly, I. Zartova, C. Ekstroem, Marek Jacewicz, B. Morosov, G. Ivanov, T. Johansson, W. Oelert, Magnus Wolke, K. Fransson, K. Schoenning, A. Povtorejko, Pawel Marciniewski, B. Shwartz, J. Stepaniak, V. Tikhomirov, A. Kuzmin, K. Lindberg, A. Turowiecki, E. Jiganov, Chr. Bargholtz, J. Zabierowski, M. Bashkanov, D. Bogoslawsky, Y. Petukhov, B. Hoeistad, Jozef Zlomanczuk, S. Kullander, M. Berłowski, T. Skorodko, Hans Calén, P. Thoerngren Engblom, L. Geren, Wolfgang Scobel, H. Petrén, S. Keleta, O. Khakimova, and Leif Gustafsson
Subjects: Physics, Nuclear and High Energy Physics, Particle physics, Meson, media_common.quotation_subject, Eta meson, Kinetic energy, Asymmetry, Nuclear physics, Amplitude, Isospin, ddc:530, Invariant mass, Nucleon, media_common
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.
Published: 2010

48. Experimental and theoretical indications for an intermediate σ-dressed dibaryon in the NN interaction

Author: T. Skorodko, P. Grabmayr, Kh.U. Abraamyan, M. Bashkanov, V. I. Kukulin, V. N. Pomerantsev, Amand Faessler, and H. Clement
Subjects: Physics, Particle physics, Roper resonance, Scattering, Nuclear Theory, General Physics and Astronomy, Sigma, Nuclear Experiment, Nucleon, Low Mass, Scalar field
Abstract: Numerous theoretical and experimental arguments are presented in favor of the generation of intermediate $\sigma$-dressed dibaryon in $NN$ interaction at intermediate and short distances. We argue that this intermediate dibaryon can be responsible for the strong intermediate-range attraction and the short-range repulsion in the $NN$ interaction, and also for the short-range correlations in nuclei. The suggested mechanism for the $\sigma$-dressing of the dibaryon is identical to that which explains the Roper resonance structure, its dominant decay modes and its extraordinary low mass. A similar transformation mechanism from the glue to the scalar field was discovered in $J/\Psi$ decays. The new experimental data on 2$\pi$-production in the scalar-isoscalar channel produced in $pn$- and $pd$-collisions and in particular the very recent data on $\gamma\gamma$ correlations in $p$C and $d$C scattering in the GeV region seems to corroborate the existence of the $\sigma$-dressed dibaryon in two- and three nucleon interactions.
Published: 2010

49. Influence of N∗-resonances on hyperon production in the channel pp→K+Λp at 2.95, 3.20 and 3.30 GeV/c beam momentum

Author: E. Kuhlmann, W. Schroeder, T. Sefzick, M. Abdel-Bary, S. Dshemuchadse, B. Jakob, P. Zupranski, P. Schoenmeier, C. Fanara, J. Hauffe, N. Paul, K. Ehrhardt, J. Dietrich, H. Jaeger, A. Erhardt, K. Kilian, S. AbdEl-Samad, H. P. Morsch, S. Marcello, S. Wirth, J. Waechter, S. Marwinski, W. Gast, G. J. Wagner, A. Wilms, H. Moertel, Marc Wagner, M. Krapp, K. Moeller, W. Eyrich, D. Hesselbarth, P. Wintz, J. Gottwald, P. Wüstner P Zupranski, H. Clement, A. Teufel, A. Metzger, Herbert Koch, C. Plettner, J. Ritman, E. Dorochkevitch, W. Ullrich, M. Fritsch, A. Schamlott, Leonhard Karsch, A. Filippi, Jens-Christoph Georgi, L. Naumann, A. Gillitzer, C. Pizzolotto, F. Stinzing, S. Mauro, M. Steinke, K. Brinkmann, W. Meyer, S. Reimann, Wüstner, M. Schulte-Wissermann, J. Kress, A. Lehmann, P. Michel, L. Pinna, H. Freiesleben, M. Richter, R. Wenzel, G. Y. Sun, Detlef Filges, R. Jaekel, and E. Roderburg
Subjects: Nuclear physics, Momentum, Physics, Nuclear and High Energy Physics, Spectrometer, Hyperon, Resonance, Dalitz plot, Production (computer science), Lambda, Beam (structure)
Abstract: Hyperon production in the threshold region was studied in the reaction pp → K + Λ p using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering the full phase-space, were taken at the three different beam momenta of p beam = 2.95 , 3.20 and 3.30 GeV/c, corresponding to excess energies of e = 204 , 285 and 316 MeV, respectively. Total cross-sections were deduced for the three beam momenta to be 23.9 ± 0.8 ± 2.0 μb , 28.4 ± 1.3 ± 2.2 μb and 35.0 ± 1.3 ± 3.0 μb . Differential observables including Dalitz plots were obtained. The analysis of the Dalitz plots reveals a strong influence of the N ( 1650 ) -resonance at p beam = 2.95 GeV / c , whereas for the higher momenta an increasing relative contribution of the N ( 1710 ) - and/or of the N ( 1720 ) -resonance was observed. In addition, the pΛ-final-state interaction turned out to have a significant influence on the Dalitz plot distribution.
Published: 2010

50. High resolution study of the Λp final state interaction in the reaction p+p→K++(Λp)

Author: A. Magiera, A. Sibirtsev, R. Jahn, E. Dorochkevitch, A. Chatterjee, M. Lesiak, K. Kilian, D. Kolev, G. J. Wagner, H. Clement, K. Ulbrich, A. Budzanowski, Di. Kirillov, G. Martinska, R. Siudak, R. Joosten, J. Ritman, R. Tsenov, N.M. Piskunov, J. Urban, B. J. Roy, P. Hawranek, M. Kravcikova, F. Hinterberger, S. Kliczewski, Da. Kirillov, I.M. Sitnik, P. von Rossen, and Hartmut Machner
Subjects: Nuclear reaction, Physics, Nuclear and High Energy Physics, Scattering, Mass spectrum, High resolution, Invariant mass, State (functional analysis), Singlet state, Physik (inkl. Astronomie), Atomic physics, Spectral line
Abstract: The reaction p p → K + + ( Λ p ) was measured at T p = 1.953 GeV and Θ = 0 ° with a high missing mass resolution in order to study the Λp final state interaction. The large final state enhancement near the Λp threshold can be described using the standard Jost-function approach. The singlet and triplet scattering lengths and effective ranges are deduced by fitting simultaneously the Λp invariant mass spectrum and the total cross section data of the free Λp scattering.
Published: 2010

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