Higgs-mediated FCNCs: Natural Flavour Conservation vs. Minimal Flavour Violation

TL;DR

This paper compares Natural Flavour Conservation and Minimal Flavour Violation hypotheses in two-Higgs doublet models, showing MFV's superior stability in suppressing FCNCs and its implications for meson mixing and CP violation.

Contribution

It demonstrates that MFV provides a more stable suppression of FCNCs than NFC when quantum corrections are included, and explores phenomenological implications for CP violation and meson mixing.

Findings

MFV is more stable than NFC in suppressing FCNCs with quantum corrections.

Two-Higgs doublet models with MFV can accommodate large CP-violating phases.

MFV models can explain anomalies in Bs mixing and epsilon_K relations.

Abstract

We compare the effectiveness of two hypotheses, Natural Flavour Conservation (NFC) and Minimal Flavour Violation (MFV), in suppressing the strength of flavour-changing neutral-currents (FCNCs) in models with more than one Higgs doublet. We show that the MFV hypothesis, in its general formulation, is more stable in suppressing FCNCs than the hypothesis of NFC alone when quantum corrections are taken into account. The phenomenological implications of the two scenarios are discussed analysing meson-antimeson mixing observables and the rare decays B -> mu+ mu-. We demonstrate that, introducing flavour-blind CP phases, two-Higgs doublet models respecting the MFV hypothesis can accommodate a large CP-violating phase in Bs mixing, as hinted by CDF and D0 data and, without extra free parameters, soften significantly in a correlated manner the observed anomaly in the relation between epsilon_K and S_psi_K.