Spin dependence of η meson production in proton-proton collisions close to threshold

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} 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 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 η meson.

arXiv commentAccepted for publication in Phys. Rev. Lett

References in corpus (23)

• The Spin Structure of the Nucleon
• Meson production in nucleon--nucleon collisions close to the threshold
• The WASA Detector Facility at CELSIUS
• Close-to-threshold Meson Production in Hadronic Interactions
• Comparison of eta and eta' production in the pp -> pp eta(eta') reactions near threshold
• Near-Threshold eta Meson Production in Proton-Proton Collisions
• Experimental study of pp eta dynamics in the pp --> ppeta reaction
• Eta Meson Production in NN Collisions
• The production of eta-mesons in nucleon-nucleon collisions near threshold
• Gluons and the eta' nucleon coupling constant
• Measurement of the Eta Production in Proton Proton Collisions with the COSY Time of Flight Spectrometer
• An analysis of the reaction pp --> ppηnear threshold
• Production of $\eta$ and ${\eta }^{\prime }$ Mesons on Nucleons and Nuclei
• Mechanism of the close-to-threshold production of the eta meson
• Phenomenology of pp->pp eta reaction close to threshold
• The Reaction $pp\to pp\eta$ and the eta-Nucleon and Nucleon-Nucleon Interactions
• Near threshold production of the eta meson via the quasi-free pn --> pn eta reaction
• Eta meson production in nucleon-nucleon collisions within an effective Lagrangian model
• Analysing power A_y in the reaction p(pol) p --> p p eta close to threshold
• Measurements of Branching Ratios for $\eta$ Decays into Charged Particles
• Invariant mass distributions for the pp to p p eta reaction at Q=10 MeV
• Etaprime interactions with nucleons and nuclei
• Study of the eta meson production with polarized proton beam

Cited by in corpus (1)

• Etaprime and Eta Mesons with Connection to Anomalous Glue