Exclusive radiative Higgs decays as probes of light-quark Yukawa couplings

Abstract

We present a detailed analysis of the rare exclusive Higgs boson decays into a single vector meson and a photon and investigate the possibility of using these processes to probe the light-quark Yukawa couplings. We work with an effective Lagrangian with modified Higgs couplings to account for possible new-physics effects in a model-independent way. The h → V γ decay rate is governed by the destructive interference of two amplitudes, one of which involves the Higgs coupling to the quark anti-quark pair inside the vector meson. We derive this amplitude at next-to-leading order in α s using QCD factorization, including the resummation of large logarithmic corrections and accounting for the effects of flavor mixing. The high factorization scale µ ∼ m h ensures that our results are rather insensitive to the hadronic parameters characterizing the light-cone distribution amplitude of the vector meson. The second amplitude arises from the loop-induced effective hγγ * and hγZ * couplings, where the off-shell gauge boson converts into the vector meson. We devise a strategy to eliminate theoretical uncertainties related to this amplitude to almost arbitrary precision. This opens up the possibility to probe for O(1) modifications of the c-and b-quark Yukawa couplings and O(30) modifications of the s-quark Yukawa coupling in the high-luminosity LHC run. In particular, we show that measurements of the ratios Br(h → Υ(nS) γ)/Br(h → γγ) and Br(h → bb)/Br(h → γγ) can provide complementary information on the real and imaginary parts of the b-quark Yukawa coupling. More accurate measurements would be possible at a future 100 TeV proton-proton collider.

B →Vℓ+ℓ− in the Standard Model from light-cone sum rules

“…The results of f K * is consistent with [103], φ-ω is treated similarly to [104], whereas our discussion on ρ-ω mixing is more detailed in terms of explicit results. We would like to add a comment concerning QED corrections.…”

Exclusive weak radiative Higgs decays in the standard model and beyond

“…As a consequence, both pseudoscalar and vector mesons can be produced, whereas in the case of h → M γ decays M could only be a (transversely polarized) vector meson [5][6][7]. The relevant Feynman diagrams for the decays h → M Z are depicted in figure 1.…”

“…The loop functions A f , A γZ W and B f are given in appendix D of [7]. Note that A f and B f are strongly suppressed for all fermions except the top quark.…”

“…The case V = γ has already been studied in great detail in [3][4][5][6][7]. The corresponding decay amplitudes receive contributions from two types of decay topologies, which interfere destructively: the "direct contributions", which involve the coupling of the Higgs boson to the quarks forming the meson, and the "indirect contributions", in which the Higgs decays to an off-shell vector boson that converts to the meson JHEP12(2016)037 through a local matrix element.…”

The leading twist light-cone distribution amplitudes for the S-wave and P-wave Bc mesons

“…This makes it possible to study many rare and even very rare decays of W , Z and Higgs bosons experimentally in the near future. Recently, there are a number of theoretical researches on exclusive radiative decays of W , Z and Higgs bosons, including decays to a photon and a quarkonium or a B c meson, within the collinear factorization, in order to test the QCD precisely or probe the Yukawa couplings of light quarks [33][34][35][36][37][38][39]. Thus, our results can be applied to such processes.…”