Probing Higgs couplings to light quarks via Higgs pair production

Abstract

One of the puzzles of the SM is the large hierarchy between the Yukawa couplings of different flavours. Yukawa couplings of the first and the second generation are constrained only very weakly so far. However, one can obtain large deviations in the Yukawa couplings in several New Physics (NP) models, such as e.g. models with new vector-like quarks, or new Higgs bosons that couple naturally to individual fermion families. In this work, we investigate the potential bounds on the NP Higgs Yukawa couplings modification κ f for light quarks from double-Higgs at the LHC, starting from a model independent formalism. We have looked at the two Higgs boson final state bbγγ, and the relevant experimental cuts to reduce backgrounds and estimated the potential exclusion bounds for κ f . We have considered both linear and non-linear effective field theory for the Higgs light quark coupling modifications.

Putting standard model EFT fits to work

“…Consistent models with large Yukawa couplings to the first and second generations can also be constructed[56][57][58].…”

Probing light Yukawa couplings in Higgs pair production

“…We hence directly include into fig. 4 final states with c-quarks, which depends on the c-tagging working points as discussed also in [3,16,22]. The expected sensitivity limits for the charm quark Yukawa modifications are an improvement compared to the current direct bounds and prospects for the HL-LHC, see [16,22].…”

“…and V q L/R denote the transformation matrices from current to mass eigenstates. It has been shown in [1,2,3] that it is possible to introduce large modifications to the Yukawa couplings without flavour-changing neutral currents (FCNCs) at tree-level, which strongly constrain off-diagonal couplings [4], and without assuming minimal flavour violation (MFV) [5]. Very little is known though about the flavour-diagonal Higgs coupling to light quarks, as seen from the weak bounds on these coupling modifications, cf.…”

“…1. up to NLO QCD, see [3]. The shape difference between the normalized ggF and qqA dominant distributions is used in the analysis to extract sensitivity limits on modifications of light quark Yukawa couplings.…”

Enhancing scalar productions with leptoquarks at the LHC

“…Such enhancements of the light-quark Yukawa couplings can even be probed at the LHC. An analysis of Higgs boson pair production suggests that in the future the High Luminosity LHC (HL-LHC) may offer a handle on this [53]. An updated analysis, with 3000 fb −1 of integrated luminosity suggests (though not in a fully model independent way) that it may be possible to narrow down the d-and s-quark Yukawa couplings to about 260 and 13 times to their SM values, respectively [54], i.e.,…”