标题： η介子接近阈值产生的机制 显示英文标题

标题： Mechanism of the close-to-threshold production of the eta meson

摘要： 在接近阈值的能区进行了 p(pol)p → ppη 反应的分析功率测量，束流动量分别为 p_{光束}= 2.010 和 2.085 GeV/c，对应的过剩能量分别为 Q = 10 和 36 MeV。 确定的分析功率基本上与零一致，这表明在两种过剩能量下，η 介子主要以 s 波形式产生。 分析功率的角度依赖性，结合之前确定的核子-核子碰撞中 η 介子产生的总截面的同位旋依赖性，揭示了核子激发到 S_{11}(1535) 共振（η 介子产生的中间过程）主要是由于碰撞核子之间的 π 介子交换，这一指示具有统计显著性。 显示英文摘要

摘要： Measurements of the analysing power for the p(pol)p --> ppeta reaction have been performed in the close-to-threshold energy region at beam momenta of p_{beam}=2.010 and 2.085 GeV/c, corresponding to excess energies of Q=10 and 36 MeV, respectively. The determined analysing power is essentially consistent with zero implying that the eta meson is produced predominantly in the s-wave at both excess energies. The angular dependence of the analysing power, combined with the hitherto determined isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal a statistically significant indication that the excitation of the nucleon to the S_{11}(1535) resonance, the process which intermediates the production of the eta meson, is predominantly due to the exchange of the pi meson between the colliding nucleons.