Cos(4 phi) azimuthal anisotropy in small-x DIS dijet production beyond the leading power TMD limit

TL;DR

This paper calculates the first correction to the quadrupole operator in high-energy QCD, revealing a new cos 4 phi angular dependence in DIS dijet production beyond the leading TMD approximation.

Contribution

It introduces the first correction beyond the TMD limit for the quadrupole operator, uncovering a novel cos 4 phi angular distribution in high-energy QCD dijet production.

Findings

Discovery of cos 4 phi angular dependence in DIS dijet production

First correction to quadrupole operator beyond TMD limit

Suppression of correction by inverse squared dijet transverse momentum

Abstract

We determine the first correction to the quadrupole operator in high-energy QCD beyond the TMD limit of Weizsaecker-Williams and linearly polarized gluon distributions. These functions give rise to isotropic resp. ~ cos 2 phi angular distributions in DIS dijet production. On the other hand, the correction produces a ~ cos 4 phi angular dependence which is suppressed by one additional power of the dijet transverse momentum scale (squared) P^2.