RIP $$ Hb\overline{b} $$: how other Higgs production modes conspire to kill a rare signal at the LHC
Davide Pagani, Hua-Sheng Shao, Marco Zaro
Abstract
A bstract The hadroproduction of a Higgs boson in association with a bottom-quark pair ( $$ Hb\overline{b} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Hb</mml:mi><mml:mover><mml:mi>b</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math> ) 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 $$ Hb\overline{b} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Hb</mml:mi><mml:mover><mml:mi>b</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math> 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 rates of these backgrounds are very large with respect to the “genuine” and y b -dependent $$ Hb\overline{b} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Hb</mml:mi><mml:mover><mml:mi>b</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math> 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 $$ Hb\overline{b} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Hb</mml:mi><mml:mover><mml:mi>b</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math> 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.