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