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arXiv · 1710.05698

Linearly-polarized small-x gluons in forward heavy-quark pair production

Cyrille Marquet·Claude Roiesnel·Pieter Taels
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Abstract

We use the Color Glass Condensate (CGC) framework to study the production of forward heavy quark-antiquark pairs in unpolarized proton-nucleus or proton-proton collisions in the small-x regime. In the limit of nearly back-to-back jets, the CGC result simplifies into the transverse-momentum dependent (TMD) factorization approach. For massless quarks, the TMD factorization formula involves three unpolarized gluon TMDs: the Weizs\"{a}cker-Williams gluon distribution, the adjoint-dipole gluon distribution, and an additional one. When quark masses are kept non-zero, three new gluon TMDs appear -- each partnered to one of the aforementioned distributions -- which describe the distribution of linearly-polarized gluons in the unpolarized small-x target. We show how these six gluon TMDs emerge from the CGC formulation and we determine their expressions in terms of Wilson line correlators. We calculate them analytically in the McLerran-Venugopalan model, and further evolve them towards smaller values of x using a numerical implementation of JIMWLK evolution.

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Cyrille Marquet, Claude Roiesnel, Pieter Taels. 2017-10-16. Linearly-polarized small-x gluons in forward heavy-quark pair production. https://doi.org/10.1103/physrevd.97.014004

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