Color transparency in $\bar p d \to \pi^- \pi^0 p$ reaction

TL;DR

This paper investigates color transparency effects in antiproton-deuteron reactions producing two pions, showing how rescattering suppression influences nuclear transparency and can be studied at PANDA.

Contribution

It models color transparency in $ar p d o ext{pions} + p$ reactions using generalized eikonal approximation, highlighting the impact on nuclear transparency ratios.

Findings

Color transparency suppresses rescattering amplitudes.

Nuclear transparency ratio shows complex dependence on kinematics.

Effects are detectable at PANDA with reasonable statistics.

Abstract

We consider exclusive two-pion production in antiproton-deuteron interactions at the beam momenta around 10 GeV/c in the kinematics with large momentum transfer in the underlying hard process $\bar p n \to \pi^- \pi^0$. The calculations are performed taking into account the antiproton and pion soft rescattering on the spectator proton in the framework of the generalized eikonal approximation. We focus on the color transparency effect that is modeled by introducing the dependence of rescattering amplitudes on the relative position of the struck and spectator nucleons along the momentum of a fast particle. As a consequence of the interplay between the impulse approximation and rescattering amplitudes the nuclear transparency ratio reveals a pretty complicated behaviour as a function of the transverse momentum of the spectator proton and the relative azimuthal angle between the $\pi^-$-meson and the proton. Color transparency significantly suppresses rescattering amplitudes which leads to substantial modifications of the nuclear transparency ratio moving it closer to the value obtained in the impulse approximation. By performing the Monte-Carlo analysis we determine that this effect can be studied at PANDA with a reasonable statistics.