# Azimuthal asymmetries in exclusive four-particle "Drell-Yan" events, with lepton-antilepton plus proton-antiproton detection, in proton-antiproton scattering

## TL;DR

This paper investigates azimuthal asymmetries in exclusive proton-antiproton collisions producing a lepton pair and a proton-antiproton pair, highlighting the role of Boer-Mulders effects and soft rescattering in generating observable asymmetries.

## Contribution

It introduces a parton-level Monte Carlo model demonstrating how Boer-Mulders functions and soft rescattering lead to azimuthal asymmetries in exclusive p-pbar collisions.

## Key findings

- Cos(2phi) asymmetries are generated in dilepton and hadron distributions.
- Hadron and lepton asymmetries are of comparable size.
- The model links momentum conservation and spectator interactions to observable asymmetries.

## Abstract

I study hard collisions between unpolarized protons and antiprotons where a lepton-antilepton pair is detected in coincidence with a final proton-antiproton pair, and no more particles are produced, in the regime 10 GeV^2 << s << 1000 GeV^2, M > 4 GeV, q_T < 3 GeV/c. The present work is centered on azimuthal asymmetries. Because of momentum conservation, a Boer-Mulders term in the momentum distribution of a quark implies a balancing effect in the momentum distribution of some spectators. This produces azimuthal asymmetries of the final hadrons. To analyze this, I have organized a parton-level MonteCarlo generator where a standard cos(2phi)-asymmetry of the dilepton distribution is produced, thanks to a soft rescattering process between an active quark coming from a hadron and a spectator anti-diquark coming from the other hadron. This produces cos(2phi)-asymmetries of the final hadron pair. Hadron and lepton asymmetries have the same size.