Next-to-leading order simulations with Sherpa+OpenLoops

We report on the SHERPA+OPENLOOPS framework for fully automated simulations of scattering processes at next-to-leading order. OPENLOOPS performs the fast evaluation of one-loop matrix elements and is interfaced to the SHERPA Monte Carlo event generator. The framework is applied to t tb b production with massive b-quarks, matched to the SHERPA parton shower. The finite bquark mass allows us to extend the kinematics to collinear b-quarks from g b b splittings. We find that this splitting mechanism has a significant impact in the t tH(b b) signal region. Furthermore we address t t production in conjunction with up to two jets merged with the MEPS@NLO method, resulting in a unified description of top-pair plus multi-jet production.