  Theoretical uncertainties in the simulation of ttbb production represent one
of the main obstacles that still hamper the observation of Higgs-boson
production in association with top-quark pairs in the H->bb channel. In this
letter we present a next-to-leading order (NLO) simulation of ttbb production
with massive b-quarks matched to the Sherpa parton shower. This allows one to
extend NLO predictions to arbitrary ttbb kinematics, including the case where
one or both b-jets arise from collinear g->bb splittings. We find that this
splitting mechanism plays an important role for the ttH(bb) analysis.

High Energy Physics - Phenomenology