RIP $H b \bar b$: How other Higgs production modes conspire to kill a rare signal at the LHC

Journal of high energy physics 11, 036 (2020). doi:10.1007/JHEP11(2020)036
The hadroproduction of a Higgs boson in association with a bottom-quark pair ($H b \bar b$) 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 ($gg$F). In this paper we calculate for the first time the so-called QCD and electroweak complete-NLO predictions for $H b \bar b$ production, using the four-flavour scheme. Our calculation shows that not only the $gg$F but also the $ZH$ and even the vector-boson-fusion channels are sizeable irreducible backgrounds. Moreover, we demonstrate that, at the LHC, the rate of these backgrounds is very large with respect to $H b \bar b$ production and in particular no suppression occurs at the differential level. Therefore, they survive typical analysis cuts. This fact further jeopardises the experimental measurement of SM $H b \bar b$ production at the LHC. Especially, unless the $y_b$ 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.
Published by SISSA, [Trieste]