Resonances contribution to two-photon exchange effects and possible large forward-backward asymmetry in $e^{+}{e}^{-}\to p\bar{p}$

Abstract

The resonances (${\eta }_c,{\chi }_{c0,c2}$) contribution to two-photon exchange (TPE) effects in $e^{+}{e}^{-}\leftrightarrow p\bar{p}$ is calculated in a simple hadronic model. The calculation shows the TPE contributions by resonance ${\chi }_{c2}$, which are dependent on the unknown phases ${\varphi }_{E,M}$ of proton's time-like form factors $G_{E,M}$, are much larger than the TPE contributions by non-resonance and are comparable with measurement precision of coming PANDA detector at $\sqrt{s}\sim M_{{\chi }_{c2}}$ for most ${\varphi }_{E,M}$.

Comments: 8 pages, 6 figures; a global factor in the calculation is corrected