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

Abstract

The process $e^{+}{e}^{-}\to N\bar{N}$ is studied nearby a threshold with account for polarizations of all initial and final particles. The nucleon polarization ${\mathbf{\zeta }}^N$ 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 ${\mathbf{\zeta }}^N$ 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 $|{\mathbf{\zeta }}^N|$ is high enough in a rather wide energy range above the threshold. Being especially high for longitudinally polarized beams, $|{\mathbf{\zeta }}^N|$ is noticeable even if both $e^{+}{e}^{-}$ beams are unpolarized.

10 pages,6 figures

References in corpus (5)

• Study of e+e- --> Lambda anti-Lambda, Lambda anti-Sigma0, Sigma0 anti-Sigma0 using Initial State Radiation with BABAR
• The antinucleon-nucleon interaction at low energy : annihilation dynamics
• Paris nucleon-antinucleon potential constrained by recent antiprotonic-atom data and antineutron-proton total cross sections
• On the strong energy dependence of the e^+e^- to ppbar amplitude near threshold
• Spin effects in $p\bar{p}$ interaction and their possible use to polarize antiproton beams

Cited by in corpus (3)

• The electromagnetic form factors of the proton in the timelike region
• Dispersion-theoretical analysis of the electromagnetic form factors of the nucleon: Past, present and future
• Final state Coulomb interaction and asymmetry of pair production close to threshold in $e^{+}{e}^{-}$ annihilation