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arXiv 1012.4638hep-ph
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阈附近$e^+e^-\to N\bar{N}$过程中的核子极化

Nucleon polarization in the process $e^+e^-\to N\bar{N}$ near threshold

A. E. Bondar, V. F. Dmitriev, A. I. Milstein, V. M. Strakhovenko

摘要:

考虑到初始粒子和最终粒子的极化,在阈值附近研究了过程$e^+e^- \rightarrow N\bar N$。核子极化$\bm ζ^N$显示出强烈的能量依赖性,这是由于核子的末态相互作用引起的核子电磁形状因子$G_E(Q^2)$和$G_M(Q^2)$的能量依赖性。它示出,这些形状因子和它们的相对相位的比率的模量可以通过测量$\bm ζ^N$连同微分截面来确定。使用Paris $N\bar N$光学势分析偏振度以计算形状因子。事实证明,在高于阈值的相当宽的能量范围内,$|\bm ζ^N|$足够高。由于对于纵向偏振光束特别高,因此即使两个$e^+e^-$光束都是非偏振的,$|\bm ζ^N|$也是明显的。

英文摘要:

The process $e^+e^- \rightarrow N\bar N$ is studied nearby a threshold with account for polarizations of all initial and final particles. The nucleon polarization $\bm ζ^N$ reveals a strong energy dependence due to that of the nucleon electromagnetic form factors $G_E(Q^2)$ and $G_M(Q^2)$ caused by the final-state interaction of nucleons. It is shown that the modulus of the ratio of these form factors and their relative phase can be determined by measuring $\bm ζ^N$ along with the differential cross section. The polarization degree is analyzed using Paris $N\bar N$ optical potential for calculation of the form factors. It turns out that $|\bm ζ^N|$ is high enough in a rather wide energy range above the threshold. Being especially high for longitudinally polarized beams, $|\bm ζ^N|$ is noticeable even if both $e^+e^-$ beams are unpolarized.

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