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

Abstract

We compute bottom mass (mb) corrections to the transverse momentum (qT) spectrum of Higgs bosons produced by gluon fusion in the regime qT ∼ mb ≪ mH at leading power in mb/mH and qT/mH, 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 qT. 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 mb ≠ 0 our results allow to determine the resummed Higgs qT distribution in the top-induced gluon fusion channel at NNLL′ (and eventually N3LL) with full dependence on mb/qT. 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 qT spectrum. Upon resummation they may thus be relevant for state-of-the-art precision predictions for the LHC.