# Triple Regge exchange mechanisms of four-pion continuum production in the $pp \to pp \pi^{+}\pi^{-}\pi^{+}\pi^{-}$ reaction

## TL;DR

This paper models exclusive four-pion production in high-energy proton-proton collisions via triple Regge exchange, estimating cross sections and distributions, and assesses detectability at LHC experiments.

## Contribution

It introduces a Regge-based model for four-pion production with triple Regge exchange and provides detailed predictions for cross sections and distributions, including experimental detection considerations.

## Key findings

- Cross section estimated at 1-5 μb for the full phase space.
- Large four-pion invariant masses are accessible via this mechanism.
- ATLAS and CMS can potentially identify the process at high invariant masses.

## Abstract

We consider exclusive multi-peripheral production of four charged pions in proton-proton collisions at high energies with simultaneous exchange of three pomerons/reggeons. The amplitude(s) for the genuine $2 \to 6$ process are written in the Regge approach. The calculation is performed with the help of the GenEx Monte Carlo code. Some corrections at low invariant masses in the two-body subsystems are necessary for application of the Regge formalism. We estimate the corresponding cross section and present differential distributions in rapidity, transverse momenta and two- and four-pion invariant masses. The cross section and the distributions depend on the value of the cut-off parameter of a form factor correcting amplitudes for off-shellness of $t$-channel pions. Rather large cross section is found for the whole phase space ($\sigma \sim$ 1-5 $\mu$b, including absorption corrections). Relatively large four-pion invariant masses are populated in the considered diffractive mechanism compared to other mechanisms discussed so far in the context of four-pion production. We investigate whether the triple Regge exchange processes could be identified with the existing LHC detectors. We consider the case of ATLAS and ALICE cuts. The ATLAS (or CMS) has better chances to identify the process in the region of large invariant masses $M_{4 \pi} > 10$ GeV. In the case of the ALICE experiment the considered mechanism competes with other mechanisms (production of $\sigma \sigma$, $\rho \rho$ pairs or single resonances) and cannot be unambiguously identified.