This title appears in the Scientific Report :
2018
Please use the identifier:
http://hdl.handle.net/2128/19784 in citations.
Please use the identifier: http://dx.doi.org/10.1103/PhysRevLett.120.022002 in citations.
Spin Dependence of η Meson Production in Proton-Proton Collisions Close to Threshold
Spin Dependence of η Meson Production in Proton-Proton Collisions Close to Threshold
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 →pp→ppη has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the pre...
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Please use the identifier: http://dx.doi.org/10.1103/PhysRevLett.120.022002 in citations.
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 →pp→ppη 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 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. |