Light quark Yukawas in triboson final states

Abstract

Triple heavy vector boson production, pp → VVV (V = W, Z), has recently been observed for the first time. We propose that precision measurements of this process provide an excellent probe of the first generation light quark Yukawa couplings. Modified quark interactions with the off-shell Higgs in this process lead to a rapid growth of the partonic cross sections with energy, which manifests in an enhanced pT distribution of the final state leptons and quarks. We quantify this effect and estimate the present and future 2σ sensitivity to the up, down, and strange Yukawas. In particular, we find that HL-LHC can reach $$ \mathcal{O}(400) $$ O 400 sensitivity to the down Yukawa relative to the Standard Model value, improving the current sensitivity in this process by a factor of 10, and which can be further improved to $$ \mathcal{O}(30) $$ O 30 at FCC-hh. This is competitive with and complementary to constraints from global fits and other on-shell probes of the first generation Yukawas. The triboson sensitivity at HL-LHC corresponds to probing dimension-6 SMEFT operators suppressed by an $$ \mathcal{O}(1) $$ O 1 TeV scale, similarly to other LHC Higgs probes.

Top, Higgs, diboson and electroweak fit to the Standard Model effective field theory

“…riety of studies of the SMEFT, for example, in electroweak processes [106][107][108][109][110][111], flavour physics [112][113][114][115][116][117][118][119][120], low-energy precision data [121][122][123], diboson measurements [124][125][126][127][128][129][130][131], at dimension 8 [87,88,[132][133][134][135][136] (where collider positivity constraints are particularly relevant [136][137][138][139][140]), and its connection with UV-complete models, both at tree-level [141][142][143][144][145][146][147] and one-loop [148][149][150]…”

“…The higher energies at the LHC also allow certain measurements of diboson and dilepton final states to become competitive with LEP [126,[185][186][187][188][189]196], enable complementary probes of higher-dimensional operators [111,197], and, moreover, give access to top physics with higher statistics than ever before, including the previously unreachable ttW/Z/H and other, rare production processes such as four-top production [168,[190][191][192]. More operators, under less restrictive flavour assumptions, can then be included in a global SMEFT fit.…”

Off-shell probes of the Higgs Yukawa couplings: light quarks and charm

“…Modifications to the Higgs Yukawa coupling spoil these delicate cancellations and lead to energy-growing amplitudes. We review the main results of the study in [17], which relies on this effect.…”

Precision test of the muon-Higgs coupling at a high-energy muon collider

“…The clean environment of a muon collider is optimally suited to separate such final states irrespective of their decay modes, and thus to guide model building in either direction, depending on the pattern actually observed in data. The formalism set up here is very similar to the one used in [83] for searching deviations in the charm and strange Yukawa couplings in multi-boson production at the LHC and FCC-hh.…”