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.

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.