Production of a pion in association with a high-Q2dilepton pair in antiproton-proton annihilation at GSI-FAIR

Abstract

We evaluate the cross section for $\overline{p}p\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ in the forward direction and for a large lepton pair invariant mass. In this kinematical region, the leading-twist amplitude factorizes into a short-distance matrix element, long-distance antiproton-distribution amplitudes, and proton to pion transition distribution amplitudes (TDAs). Using a modeling inspired from the chiral limit for these TDAs, we obtain a first estimate of this cross section, which demonstrates that this process can be measured at GSI-FAIR.