Non commutativity between massless and soft limit in processes with heavy quarks

Abstract

Processes involving heavy quarks can be computed in perturbation theory in two different ways: we can adopt a scheme in which the mass of the quark is considered only as a regulator of the collinear divergences because of the fact that the hard scale of the process is far bigger or we can consider the quark as a massive particle. Each picture has its own advantages and drawbacks: we investigate the differences between the two approaches with particular attention to the soft logarithmic structure. We examine the origin of this difference, focusing on different processes involving the Higgs boson . Finally we perform the threshold resummation of the Higgs boson decay rate into a $b\bar{b}$ pair at NLL accuracy in the massive scheme.