Transverse Parton Distribution and Fragmentation Functions at NNLO: the Gluon Case

TL;DR

This paper computes gluon transverse momentum dependent distribution and fragmentation functions at NNLO, revealing new results and discrepancies, and applies these to Higgs decay processes.

Contribution

It provides the first NNLO calculations of gluon TMDPDFs and TMDFFs using the exponential regulator, including a new momentum sum rule and a two-loop gluon jet function.

Findings

Results for unpolarized and linearly polarized distributions at NNLO.

Discrepancy found with previous literature for linearly polarized gluon TMDPDFs.

Derived a nontrivial momentum conservation sum rule in super-Yang-Mills theory.

Abstract

We calculate in this paper the perturbative gluon transverse momentum dependent parton distribution functions (TMDPDFs) and fragmentation functions (TMDFFs) using the exponential regulator for rapidity divergences. We obtain results for both unpolarized and linearly polarized distributions through next-to-next-to leading order in strong coupling constant, and through ${\cal O}(\epsilon^2)$ in dimensional regulator (finding discrepancy for the linearly polarized gluon TMDPDFs with a previous result in the literature). We find a nontrivial momentum conservation sum rule for the linearly polarized component for both TMDPDFs and TMDFFs in the ${\cal N}=1$ super-Yang-Mills theory. The TMDFFs are used to calculate the two-loop gluon jet function for the energy-energy correlator in Higgs gluonic decay in the back-to-back limit.