First results of proton antiproton annihilation into a pion pair at large scattering angles within the handbag approach

Abstract

We propose to describe the process $ p ~ \bar{p} \rightarrow \pi^+ ~ \pi^-$ in a perturbative, QCD motivated framework in which a hard $ud \, \bar{u} \bar{d} \rightarrow d \, \bar{d} $ annihilation factorizes from soft transition distribution amplitudes. We advocate that the scale allowing for this factorization is the large transverse momentum transfer. In our simplified model, in which the proton is considered as a (scalar)diqark-quark system, a transition distribution amplitude describes the non-perturbative transition of the proton to the meson by emission of a scalar, isoscalar $ ud $-diquark and absorption of an antiquark (analogously for $ \bar{p} \rightarrow \pi^- $). We model the transition distribution amplitudes as an overlap of light-cone wave functions and present first results for the differential cross section. This process will be measured by the $ \bar{\mbox{P}}$ANDA experiment at GSI-FAIR.