We evaluate the cross section for $\overline{p}p\to {\ell }^{+}{\ell }^{-}{\pi }^0$ 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.

• Received 5 October 2007

DOI:https://doi.org/10.1103/PhysRevD.76.111502