Collinear expansion for color singlet cross sections

TL;DR

This paper introduces a systematic collinear expansion method for color-singlet cross sections at hadron colliders, improving calculations of observables like Higgs production and beam functions at NNLO in QCD.

Contribution

The paper presents a new, efficient collinear expansion technique applicable to a broad class of observables, with explicit NNLO results for Higgs rapidity distribution and beam functions.

Findings

First two terms of collinear expansion for Higgs rapidity distribution at NNLO.

Extraction of universal scattering cross section components like N-jettiness and beam functions at NNLO.

Demonstration of the method's systematic improvability and broad applicability.

Abstract

We demonstrate how to efficiently expand cross sections for color-singlet production at hadron colliders around the kinematic limit of all final state radiation being collinear to one of the incoming hadrons. This expansion is systematically improvable and applicable to a large class of physical observables. We demonstrate the viability of this technique by obtaining the first two terms in the collinear expansion of the rapidity distribution of the gluon fusion Higgs boson production cross section at next-to-next-to leading order (NNLO) in QCD perturbation theory. Furthermore, we illustrate how this technique is used to extract universal building blocks of scattering cross section like the N-jettiness and transverse momentum beam function at NNLO.