Exclusive $pp \to nn \pi^{+}\pi^{+}$ reaction at LHC and RHIC

TL;DR

This paper predicts large cross sections for the exclusive $pp o nn \pi^+\pi^+$ reaction at RHIC and LHC energies using a Regge approach, highlighting interference effects and challenges in extracting elastic scattering data.

Contribution

The study provides detailed differential distribution predictions for the exclusive four-body reaction at high energies, incorporating multiple interfering mechanisms and absorption effects.

Findings

Large predicted cross sections at RHIC and LHC energies.

Interference of mechanisms complicates elastic $\pi^+\pi^+$ scattering extraction.

Differential distributions in various kinematic variables are presented.

Abstract

We evaluate differential distributions for the four-body $p p \to n n \pi^+ \pi^+$ reaction. The amplitude for the process is calculated in the Regge approach including many diagrams. We make predictions for possible future experiments at RHIC and LHC energies. Very large cross sections are found which is partially due to interference of a few mechanisms. Presence of several interfering mechanisms precludes extraction of the elastic $\pi^+ \pi^+$ scattering cross section. Absorption effects are estimated. Differential distributions in pseudorapidity, rapidity, invariant two-pion mass, transverse-momentum and energy distributions of neutrons are presented for proton-proton collisions at $\sqrt{s}$ = 500 GeV (RHIC) and $\sqrt{s}$ = 0.9, 2.36 and 7 TeV (LHC). Cross sections with experimental cuts are presented.