Full NLO QCD corrections to off-shell t(t)over-barb(b)over-bar production

In this article, we report on the computation of the next-to-leading order (NLO) QCD corrections to pp -> mu(-)(nu) over bar (mu)e+nu(e) (b) over barb (b) over barb at the LHC, which is an irreducible background to pp -> t (t) over barH(-> b (b) over bar). This is the first time that a full NLO computation for a 2 -> 8 process with 6 external strongly interacting partons is made public. No approximations are used, and all off-shell and interference effects are taken into account. Cross sections and differential distributions from the full computation are compared to results obtained by using a double-pole approximation for the top quarks. The difference between the full calculation and the one using the double-pole approximation is in general below 5% but can reach 10% in some regions of phase space.