Abstract
We study Higgs boson production in association with a top quark and a W boson at the LHC. At NLO in QCD, tWH interferes with tbar{t} H and a procedure to meaningfully separate the two processes needs to be employed. In order to define tWH production for both total rates and differential distributions, we consider the diagram removal and diagram subtraction techniques that have been previously proposed for treating intermediate resonances at NLO, in particular in the context of tW production. These techniques feature approximations that need to be carefully taken into account when theoretical predictions are compared to experimental measurements. To this aim, we first critically revisit the tW process, for which an extensive literature exists and where an analogous interference with t bar{t} production takes place. We then provide robust results for total and differential cross sections for tW and tWH at 13 TeV, also matching short-distance events to a parton shower. We formulate a reliable prescription to estimate the theoretical uncertainties, including those associated to the very definition of the process at NLO. Finally, we study the sensitivity to a non-Standard-Model relative phase between the Higgs couplings to the top quark and to the W boson in tWH production.
Highlights
As when no Higgs is present in the final state, top quark and Higgs boson associated production can proceed either via a top pair production mediated by QCD interactions, or as a single-topquark process mediated by electroweak interactions
This goal can be achieved by comparing results among different nextto-leading order (NLO) schemes, since the difference among them provides a measure of interference effects and related theoretical systematics
In this work we have provided for the first time NLO accurate predictions for the t W H process, including parton-shower effects
Summary
As when no Higgs is present in the final state, top quark and Higgs boson associated production can proceed either via a top pair production mediated by QCD interactions, or as a single-top (anti-)quark process mediated by electroweak interactions. The latter case, despite being characterised by much smaller cross sections with respect to the QCD production, displays a richness and peculiarities that make it phenomenologically very interesting. For the first two channels, this classification is unambiguous only up to nextto-leading order (NLO) accuracy if a five-flavour scheme (5FS) is used. At NLO, real corrections of the type gg → t W b(H ) arise that can feature a reso-
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