Irreducible background and interference effects for Higgs-boson   production in association with a top-quark pair
  We present an analysis of Higgs-boson production in association with a top-quark pair at the LHC investigating in particular the final state consisting of four b jets, two jets, one identified charged lepton and missing energy. We consider the Standard Model prediction in three scenarios, the resonant Higgs-boson plus top-quark-pair production, the resonant production of a top-quark pair in association with a b-jet pair and the full process including all non-resonant and interference contributions. By comparing these scenarios we examine the irreducible background for the production rate and several kinematical distributions. With standard selection criteria the irreducible background turns out to be three times as large as the signal. For most observables we find a uniform deviation of eight percent between the scenario requiring two resonant top quarks and the full process. In particular phase-space regions the non-resonant contributions cause larger effects, and we observe shape changes for some distributions. Furthermore we investigate interference effects and find that neglecting interference contributions results in an over-estimate of the total cross-section of five percent. 
Ansgar Denner, Robert Feger, Andreas Scharf
hep-ph