Production of a pion in association with a high-Q2 dilepton pair in antiproton-proton annihilation at GSI-FAIR

TL;DR

This paper estimates the cross section for antiproton-proton annihilation producing a dilepton pair and a neutral pion at GSI-FAIR, using factorization and modeling of transition distribution amplitudes.

Contribution

It provides the first estimate of this specific cross section by applying factorization and TDA modeling, suggesting the process is measurable at GSI-FAIR.

Findings

Cross section estimated for the process in the forward direction

Demonstrates the process can be measured at GSI-FAIR

Uses a chiral limit inspired TDA model

Abstract

We evaluate the cross section for anti-p p -> l+ l- pi0 in the forward direction and for large lepton pair invariant mass. In this kinematical region, the leading-twist amplitude factorises into a short-distance matrix element, long-distance dominated antiproton Distribution Amplitudes and proton to pion Transition Distribution Amplitudes (TDA). Using a modelling inspired from the chiral limit for these TDAs, we obtain a first estimate of this cross section, thus demonstrating that this process can be measured at GSI-FAIR.