Refining the GENEVA method for Higgs boson production via gluon fusion

TL;DR

This paper enhances the GENEVA method for Higgs boson production via gluon fusion by improving resummation, scale dependence handling, and numerical stability, validated against experimental data.

Contribution

It introduces specific improvements to the GENEVA matching procedure, including better resummation and scale treatment, for more accurate Higgs production predictions.

Findings

Validated NNLO accuracy against independent calculations.

Achieved good agreement with ATLAS and CMS diphoton data.

Enhanced numerical stability at small resolution parameters.

Abstract

We describe a number of improvements to the GENEVA method for matching NNLO calculations to parton shower programs. In particular, we detail changes to the resummed calculation used in the matching procedure, including disentangling the cross section dependence on factorisation and beam scales, and an improved treatment of timelike logarithms. We also discuss modifications in the implementation of the splitting functions which serve to make the resummed calculation differential in the higher multiplicity phase space. These changes improve the stability of the numerical cancellation of the nonsingular term at small values of the resolution parameter. As a case study, we consider the gluon-initiated Higgs boson production process $gg\to H$. We validate the NNLO accuracy of our predictions against independent calculations, and compare our showered and hadronised results with recent data taken at the ATLAS and CMS experiments in the diphoton decay channel, finding good agreement.