Higgs Quark Flavor Violation: Simplified Models and Status of General Two-Higgs-Doublet Model

Abstract

We study quark flavor violating interactions mediated by the Higgs boson h. We consider observables involving a third generation quark, of both the up and the down quark sectors, like h → bs and t → ch. Using an effective field theory approach we systematically list all the possible tree-level ultraviolet completions, which comprise models with vector-like quarks and/or extra scalars. We provide upper bounds on the flavor violating transitions allowed by current limits stemming from low energy processes, such as meson mixing and b → sγ. We find that scenarios with vector-like quarks always have very suppressed flavor-violating transitions, while a general two Higgs doublet model may have a sizeable rate. To study the latter case in detail, we perform a full numerical simulation taking into account all relevant theoretical and phenomenological constraints. Our results show that BR(t → ch) [BR(h → bs)] are still allowed at the subpercent [percent] level, which are being [may be] explored at the LHC [future colliders]. Finally, we have found that the mild mass-splitting discrepancy with respect to the SM in the B s meson system can be accommodated in the Two-Higgs-Doublet Model. If confirmed, it yields the prediction BR(h → bs) 10 −4 , if the new contribution to the mass-splitting is dominated by tree-level Higgs boson exchange.

Likelihood analysis of the flavour anomalies and g – 2 in the general two Higgs doublet model

“…Following [71,125] we also include the oblique parameters S, T and U , which parametrise radiative corrections to electroweak gauge boson propagators. In this study we computed these oblique parameters with the 2HDMC package and these are contrasted with the most probable values inferred from experimental data, as found by the Gfitter group [129] S = 0.05 ± 0.11, T = 0.09 ± 0.13, U = 0.01 ± 0.11,…”

“…Here, the ξ u matrix has been previously considered to be asymmetric from B s − B s oscillations constraints at one loop level and for heavy Higgs masses of order 700 GeV [130,131]. However, since we are approaching the dominant contribution process at LO and we are exploring masses in the range [0.5, 4.0] TeV as in [71], we will consider only the symmetric case, i.e., ξ u tc = ξ u ct . Hence, assuming the remaining ξ d and ξ l matrices to be symmetric as well, the total number of parameters to scan over is reduced by 3.…”

“…In addition, we also include the normalised distributions dΓ(B → Dτ ν)/(Γdq 2 ) and dΓ(B → D τ ν)/(Γdq 2 ), as measured by the BaBar collaboration [168]. Lastly, the mass difference ∆M s of B s − B s oscillations is included in our study and (for m A = m H ) is given by [71] [169,170], and the U running matrix being defined in [71]. A summary of all FCCC observables included in this study is provided in table 2.…”

“…Nevertheless, the majority of these studies have only explored solutions in restricted regions of the parameter space, with a lack of discussion of the role of (marginally) statistically preferred regions, and often considering the b → sll observables from model independent global fits [15,70]. Statistically rigorous explorations of the parameter space of the model contrasted directly to experimental constraints have rarely been performed, and even those were focused exclusively on interactions in the quark sector [71].…”

Flavored axion in the UV-complete Froggatt–Nielsen models

“…Therefore, in the DFSZ scheme of flavored axion models, scalar FCNCs are expected on minimal models. On the phenomenological side, these FCNCs are strongly constrained by processes, namely K L → μ − μ + or top decays such as t → hc, hu [57].…”