$\Delta$ contribution in $e^+ + e^- \to p + \bar{p}$ at small $s$

TL;DR

This paper investigates two-photon annihilation contributions in the process $e^+ + e^- o p + ar{p}$, showing small corrections to the unpolarized cross section and enhanced effects on polarization at small energy scales.

Contribution

It introduces a simple hadronic model including $N$ and $ riangle$ intermediate states to analyze two-photon corrections in proton-antiproton production.

Findings

Two-photon correction to unpolarized cross section is small.

Angle dependence of correction weakens at small $s$.

Correction to polarization $P_z$ is significantly enhanced.

Abstract

Two-photon annihilate contributions in the process $e^+ + e^- \to p + \bar{p}$ including $N$ and $\Delta$ intermediate are discussed in a simple hadronic model. The corrections to the unpolarized cross section and polarized observables $P_x,P_z$ are presented. The results show the two-photon annihilate correction to unpolarized cross section is small and its angle dependence becomes weak at small $s$ after considering the $N$ and $\Delta(1232)$ contributions simultaneously, while the correction to $P_z$ is enhanced.