RIP Hb b ¯ $$ Hb\overline{b} $$ : how other Higgs production modes conspire to kill a rare signal at the LHC

Abstract The hadroproduction of a Higgs boson in association with a bottom-quark pair ( Hb b ¯ $$ Hb\overline{b} $$ ) is commonly considered as the key process for directly probing the Yukawa interaction between the Higgs boson and the bottom quark (y b ). 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 Hb b ¯ $$ Hb\overline{b} $$ 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 y b -dependent Hb b ¯ $$ Hb\overline{b} $$ 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 y b -dependent component of Hb b ¯ $$ Hb\overline{b} $$ production in the SM. Especially, unless y b is significantly enlarged by new physics, even for beyond-the SM scenarios the direct determination of y b via this process seems to be hopeless at the LHC.