Bottom-quark mass effects in associated production with Z and H bosons

In this study, predictions obtained in the four and in the five flavour schemes are compared for two important processes involving heavy flavours at the LHC: the production of a Z or a Higgs boson in association with b quarks. In particular we obtain predictions with SHERPA's MC@NLO implementation for the four-flavour scheme, treating the b's as massive, and with multijet merging at leading and next-to leading order for the five-flavour scheme. While differences between the two schemes, at the inclusive level, are well understood from resummation of possibly large logs into the b-PDFs, differences in shape present a major problem for experimental measurements. We make use of data for Z+b(b) production at the 7 TeV LHC to exhibit strengths and weaknesses of the different approaches and we use these results to validate predictions for b-associated Higgs-boson production at the 13 TeV Run II.