Two-loop bottom mass effects on the Higgs transverse momentum spectrum in top-induced gluon fusion

TL;DR

This paper calculates bottom quark mass effects on the Higgs transverse momentum spectrum in gluon fusion, providing a detailed two-loop analysis that enhances precision predictions for LHC phenomenology.

Contribution

It introduces the first two-loop calculation of bottom mass effects on Higgs $q_T$ spectrum within SCET, enabling more accurate resummation including full $m_b/q_T$ dependence.

Findings

Percent-level effects in the Higgs $q_T$ peak region from bottom mass corrections.

Framework for NNLL' and N$^3$LL$'$ resummation with bottom mass dependence.

Potential impact on precision Higgs predictions at the LHC.

Abstract

We compute bottom mass ($m_b$) corrections to the transverse momentum ($q_T$) spectrum of Higgs bosons produced by gluon fusion in the regime $q_T \sim m_b \ll m_H$ at leading power in $m_b/m_H$ and $q_T/m_H$, where the gluons couple to the Higgs via a top loop. To this end we calculate the quark mass dependence of the transverse momentum dependent gluon beam functions (aka gluon TMDPDFs) at two loops in the framework of SCET. These functions represent the collinear matrix elements in the factorized gluon-fusion cross section for small $q_T$. We discuss in detail technical subtleties regarding rapidity regulators and zero-bin subtractions in the calculation of the virtual corrections present for massive quarks. Combined with the known soft function for $m_b \neq 0$ our results allow to determine the resummed Higgs $q_T$ distribution in the top-induced gluon fusion channel at NNLL$^\prime$ (and eventually N$^3$LL) with full dependence on $m_b/q_T$. We perform a first phenomenological analysis at fixed order, where the new corrections to the massless approximation lead to percent-level effects in the peak region of the Higgs $q_T$ spectrum. Upon resummation they may thus be relevant for state-of-the-art precision predictions for the LHC.