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. 2018 Jan 12;120(2):022002.
doi: 10.1103/PhysRevLett.120.022002.

Spin Dependence of η Meson Production in Proton-Proton Collisions Close to Threshold

P Adlarson  1 , W Augustyniak  2 , W Bardan  3 , M Bashkanov  4 , S D Bass  3 , F S Bergmann  5 , M Berłowski  6 , A Bondar  7   8 , M Büscher  9 , H Calén  1 , I Ciepał  10 , H Clement  11   12 , E Czerwiński  3 , K Demmich  5 , R Engels  9 , A Erven  13 , W Erven  13 , W Eyrich  14 , P Fedorets  9   15 , K Föhl  16 , K Fransson  1 , F Goldenbaum  9 , A Goswami  9   17 , K Grigoryev  9   18 , C-O Gullström  1 , L Heijkenskjöld  1 , V Hejny  9 , N Hüsken  5 , L Jarczyk  3 , T Johansson  1 , B Kamys  3 , G Kemmerling  13 , G Khatri  3 , A Khoukaz  5 , O Khreptak  3 , D A Kirillov  19 , S Kistryn  3 , H Kleines  13 , B Kłos  20 , W Krzemień  3 , P Kulessa  10 , A Kupść  1   6 , A Kuzmin  7   8 , K Lalwani  21 , D Lersch  9 , B Lorentz  9 , A Magiera  3 , R Maier  9   22 , P Marciniewski  1 , B Mariański  2 , H-P Morsch  2 , P Moskal  3 , H Ohm  9 , W Parol  10 , E Perez Del Rio  11   12 , N M Piskunov  19 , D Prasuhn  9 , D Pszczel  1   6 , K Pysz  10 , A Pyszniak  1   3 , J Ritman  9   22   23 , A Roy  17 , Z Rudy  3 , O Rundel  3 , S Sawant  24 , S Schadmand  9 , I Schätti-Ozerianska  3 , T Sefzick  9 , V Serdyuk  9 , B Shwartz  7   8 , K Sitterberg  5 , T Skorodko  11   12   25 , M Skurzok  3 , J Smyrski  3 , V Sopov  15 , R Stassen  9 , J Stepaniak  6 , E Stephan  20 , G Sterzenbach  9 , H Stockhorst  9 , H Ströher  9   22 , A Szczurek  10 , A Trzciński  2 , M Wolke  1 , A Wrońska  3 , P Wüstner  13 , A Yamamoto  26 , J Zabierowski  27 , M J Zieliński  3 , J Złomańczuk  1 , P Żuprański  2 , M Żurek  9 ; WASA-at-COSY Collaboration
Affiliations
Free article

Spin Dependence of η Meson Production in Proton-Proton Collisions Close to Threshold

P Adlarson et al. Phys Rev Lett. .
Free article

Abstract

Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high polarization degree of the proton beam of COSY, the reaction p[over →]p→ppη has been measured close to threshold to explore the analyzing power A_{y}. The angular distribution of A_{y} is determined with the precision improved by more than 1 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 reveal strong interference of Ps and Pp partial waves and cancellation of (Pp)^{2} and Ss^{*}Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the η meson.

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