# Study of resonant processes for multi-pion production in $\bar p +p\to\ell ^++\ell^- +n_\pi \pi$ annihilation

## TL;DR

This paper investigates multi-pion production in antiproton-proton annihilation using a phenomenological approach to explore properties of potential antiproton-nucleon bound states and their resonances, providing detailed cross section calculations.

## Contribution

It introduces a phenomenological model based on Compton-like amplitudes to analyze multi-pion production and predicts cross sections for various resonant states in antiproton-proton collisions.

## Key findings

- Numerical results for scalar and pseudoscalar resonant states.
- Explicit differential cross section formulas depending on invariant masses.
- Insights into properties of the hypothesized $ar N N$ atom and its resonances.

## Abstract

In frame of a phenomenological approach based on Compton-like Feynman amplitudes, we study multi-pion production in antiproton nucleon collisions. The main interest of this reaction is related to the possibility to study the properties of the presumable $\bar N N$ atom and of its resonances. For the case of formation of a scalar or pseudoscalar resonant state, with $I^G(J^{P})=1^-(0^{\pm}),~0^+(0^-)$ numerical results are obtained. The differential cross section in an experimental set-up where the pions invariant mass is measured, is given with explicit dependence on the lepton pair and pions invariant mass.