Two Gluon Emission from MHV: Two Particle Correlations and the Deviation from Poisson

TL;DR

This paper derives the two-gluon emission distribution from an off-shell quark using MHV techniques, revealing non-Abelian effects and correlations relevant to high-energy collisions and Monte Carlo modeling.

Contribution

It introduces a novel calculation of two-gluon correlations in QCD using MHV methods, highlighting non-Abelian corrections and their implications for high-multiplicity collisions.

Findings

Non-Abelian corrections deviate from Poisson distribution.

Gluon correlations resemble those in high-multiplicity collisions.

Autocorrelation may contribute to non-hydrodynamical v2 in pp and pA.

Abstract

We derive the momentum distribution for two soft and collinear gluons emitted from an off-shell quark, modeled by a $q\gamma\rightarrow qgg$ scattering process and computed using the maximal helicity violating (MHV) technique. We find the explicit non-Abelian corrections to the independent emission Poisson distribution in QED and demonstrate the efficiency of the MHV technique in perturbative QCD calculations. The gluonic two particle correlation function is highly suggestive of that measured in high-multiplicity $pp$ and $pA$ collisions, with a tight correlation in angle but broad correlation in rapidity. Further, the autocorrelation generated by the non-Abelian correlation can provide a significant non-hydrodynamical source of $v_2$ in these high multiplicity $pp$ and $pA$ collisions. Finally, these two gluon correlations can be used to calibrate Monte Carlo shower codes for a more accurate description of QCD processes in $pp$ collisions.