Associated production of a top-quark pair with vector bosons at NLO in QCD: impact on t t ¯ H tt̄H searches at the LHC

We study the production of a top-quark pair in association with one and two vector bosons, tt̄V and tt̄V0.1em V with V = γ, Z, W ±, at the LHC. We provide predictions at next-to-leading order in QCD for total cross sections and top-quark charge asymmetries as well as for differential distributions. A thorough discussion of the residual theoretical uncertainties related to missing higher orders and to parton distribution functions is presented. As an application, we calculate the total cross sections for this class of processes (together with tt̄H and tt̄tt̄ production) at hadron colliders for energies up to 100 TeV. In addition, by matching the NLO calculation to a parton shower, we determine the contribution of tt̄V and tt̄V0.1em V to final state signatures (two-photon and two-same-sign-, three-and four-lepton) relevant for tt̄H analyses at the Run II of the LHC.