标题： η介子的阈值附近产生机制 显示英文标题

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

摘要： 在接近阈值能量区域，对p(极化)p --> ppeta反应的分析功率进行了测量，束流动量分别为p_{梁}=2.010和2.085 GeV/c，分别对应过剩能量Q=10和36 MeV。 确定的分析功率基本上与零一致，这意味着在两个过剩能量下，eta介子主要以s波产生。 分析功率的角依赖性，结合迄今为止确定的eta介子在核子-核子碰撞中产生的总截面的同位旋依赖性，显示出统计上显著的迹象，表明核子激发到S_{11}(1535)共振态的过程，即介导eta介子产生的过程，主要是由于碰撞核子之间pi介子的交换。 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.