Theoretical modeling of QCD radiation in off-shell Higgs production through gluon fusion

TL;DR

This paper develops a theoretical model for QCD radiation in off-shell Higgs production via gluon fusion, aiming to enhance the precision of Higgs width measurements by improving predictions of complex quantum effects.

Contribution

It compares leading-order and next-to-leading-order predictions for off-shell Higgs production, addressing limitations of previous approximations and analyzing uncertainties in QCD effects.

Findings

Higher-order QCD effects significantly impact off-shell Higgs predictions.

Jet merging with parton showers differs from NLO computations in key aspects.

The study provides improved theoretical tools for future experimental analyses.

Abstract

The measurement of the Higgs boson width is a critical test of the Standard Model, with significant implications for understanding electroweak symmetry breaking. Direct measurements are limited by detector resolution, but it can be measured with greater precision through a combined analysis of on-shell and off-shell Higgs boson production. While results for on-shell production have been computed to a very high accuracy, theoretical predictions for off-shell Higgs boson production are not as well controlled due to the breakdown of the heavy-top approximation and the large interference with non-resonant amplitudes. Seeking to understand and improve the theoretical control, we compare leading-order and next-to-leading-order plus parton shower differential cross-sections for signal, background, and full physical processes in off-shell Higgs boson production at the Large Hadron Collider, using Powheg, MadGraph, and Sherpa. We analyze the impact of higher-order quantum chromodynamics effects and theoretical uncertainties, highlighting differences between predictions using jet merging with parton showers, and those from next-to-leading order computations matched to parton showers. The results provide insights for improving theoretical predictions and their application to experimental measurements in the future.