Heavy-flavor effects in soft gluon resummation for electroweak boson production at hadron colliders

We evaluate the impact of heavy-quark masses on transverse momentum distributions of W, Z, and supersymmetric neutral Higgs bosons at the Tevatron and LHC. The masses of charm and bottom quarks act as non-negligible momentum scales at small transverse momentum, and affect resummation of soft and collinear radiation. We point out inconsistencies in the treatment of heavy-flavor channels at small transverse momentum in massless factorization schemes, and formulate small transverse momentum resummation in a general-mass variable flavor number factorization scheme. The improved treatment of the quark mass dependence leads to non-negligible effects in precision measurements of the W boson mass at the LHC, and may cause observable modifications in production of Higgs bosons and other particles in heavy-quark scattering.