Treatment of quark masses in b-associated production at the LHC

Abstract

With the discovery of the Higgs boson at the Large Hadron Collider (LHC), and no signs of new physics to current date, precise theoretical predictions are of increasing importance. It is now essential to study in details the properties of the newly found boson, in particular its coupling to other particles and itself, as this unveils further the mechanism of symmetry breaking.
In this thesis, we extend the currently used methods to deal with heavy quarks in hadron collision processes, the four-flavour and the five-flavour scheme, to con- sistently include mass effects as well as resummation of collinear logarithms. This is done using two complementary approaches. At the inclusive level, we extend a method used to include mass effects in parton densities evolution, known as FONLL. At the differential level, we devise a five-flavour scheme that includes mass effects consistently and systematically up to MC@NLO accuracy.
We study the impact of such schemes on two phenomenologically relevant pro- cesses at the LHC: the production of a heavy boson, a Z or a Higgs, in association with heavy quarks. For these processes, in fact, the two standard schemes, have been known to largely disagree. In both new schemes, mass effects are found to have a few percent effect, with the bulk of the difference between a completely massless and a completely massive picture, residing in the resummation of collinear logarithms.