Abstract
The hadroproduction of a Higgs boson in association with a bottom-quark pair ( Hboverline{b} ) is commonly considered as the key process for directly probing the Yukawa interaction between the Higgs boson and the bottom quark (yb). However, in the Standard-Model (SM) this process is also known to suffer from very large irreducible backgrounds from other Higgs production channels, notably gluon-fusion (ggF). In this paper we calculate for the first time the so-called QCD and electroweak complete-NLO predictions for Hboverline{b} production, using the four-flavour scheme. Our calculation shows that not only the ggF but also the ZH and even the vector-boson-fusion channels are sizeable irreducible backgrounds. Moreover, we demonstrate that, at the LHC, the rates of these backgrounds are very large with respect to the “genuine” and yb-dependent Hboverline{b} production mode. In particular, no suppression occurs at the differential level and therefore backgrounds survive typical analysis cuts. This fact further jeopardises the chances of measuring at the LHC the yb-dependent component of Hboverline{b} production in the SM. Especially, unless yb is significantly enlarged by new physics, even for beyond-the SM scenarios the direct determination of yb via this process seems to be hopeless at the LHC.
Highlights
While the H→bb decay has already been observed in conjunction with V H production [5, 6, 17,18,19,20], no dedicated SM analysis has ever been performed by the ATLAS and CMS collaboration in order to measure the Hbb production process
The problem is that tagging a b-jet dramatically reduces the cross section, but as said this is an unavoidable procedure for obtaining a possible direct sensitivity on the bottom-quark Yukawa coupling
In the case of the Higgs-fermion Yukawa couplings, this translates in the need of measuring the relevant production mechanisms and/or decay modes of the Higgs boson
Summary
[57] has explored several important issues related to the computations at NLO in general Before this present publication, in the MG5_aMC framework NLO EW corrections and more in general complete-NLO predictions could be performed only in the 5FS, i.e., with massless bottom quarks. In order to perform the calculation of the complete-NLO predictions of any SM process in the 4FS, in particular Hbb as a case study in the present paper, we have extended the capabilities of MG5_aMC. The evaluation of one-loop virtual matrix elements in MG5_aMC is performed in the MadLoop module [66, 75], by using different types of techniques for Feynman one-loop integral reduction, namely, the integrand reduction (e.g., the so-called OPP [76] and Laurentseries expansion [77] methods) or tensor integral reduction [78,79,80] approaches.
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