Flavor-phenomenology of two-Higgs-doublet models with generic Yukawa structure

Abstract

In this article, we perform an extensive study of flavor observables in a two-Higgs-doublet model (2HDM) with generic Yukawa structure (of type III). This model is interesting not only because it is the decoupling limit of the Minimal Supersymmetric Standard Model (MSSM) but also because of its rich flavor phenomenology which also allows for sizable effects not only in FCNC processes but also in tauonic B decays. We examine the possible effects in flavor physics and constrain the model both from tree-level processes and from loop-observables. The free parameters of the model are the heavy Higgs mass, tan β (the ratio of vacuum expectation values) and the "non-holomorphic". In our analysis we constrain the elements ǫ f ij in various ways: In a first step we give order of magnitude constraints on ǫ f ij from 't Hooft's naturalness criterion, finding that all ǫ f ij must be rather small unless the third generation is involved. In a second step, we constrain the Yukawa structure of the type-III 2HDM from tree-level FCNC processesand µ − → e − e + e − ) and observe that all flavor off-diagonal elements of these couplings, except ǫ u 32,31 and ǫ u 23,13 must be very small in order to satisfy the current experimental bounds. In a third step, we consider Higgs mediated loop contributions to FCNC processes (b → s(d)γ, B s,d mixing, K − K mixing and µ → eγ) finding that also ǫ u 13 and ǫ u 23 must be very small, while the bounds on ǫ u 31 and ǫ u 32 are especially weak. Furthermore, considering the constraints from electric dipole moments (EDMs) we obtain constrains on some parameters ǫ u,ℓ ij . Taking into account the constraints from FCNC processes we study the size of possible effects in the tauonic B decaysand τ → K(π)ν which are all sensitive to tree-level charged Higgs exchange. Interestingly, the unconstrained ǫ u 32,31 are just the elements which directly enter the branching ratios for B → τ ν , B → Dτ ν and B → D * τ ν . We show that they can explain the deviations from the SM predictions in these processes without fine tuning. Furthermore, B → τ ν , B → Dτ ν and B → D * τ ν can even be explained simultaneously. Finally, we give upper limits on the branching ratios of the lepton flavor-violating neutral B meson decays (B s,d → µe, B s,d → τ e and B s,d → τ µ) and correlate the radiative lepton decays (τ → µγ, τ → eγ and µ → eγ) to the corresponding neutral current lepton decays (τ − → µ − µ + µ − , τ − → e − µ + µ − and µ − → e − e + e − ). A detailed appendix contains all relevant information for the considered processes for general scalar-fermion-fermion couplings.

Explaining the CMS Higgs flavor-violating decay excess

“…Since we are driven by phenomenological considerations, we use as input the scalar masses (m h , m H , m A and m H ± ) rather than the parameters in the scalar potential. Our choice of a small mass difference between the pseudoscalar and charged Higgses is motivated by the reduction of the T parameter 6 , whereas the lower limits on sin(β − α) and m H ± (as induced by the lower limit on m A ) are motivated by experimental constraints: smaller values of sin(β −α) would be excluded by current measurements of the Higgs couplings to fermions and gauge bosons while lower m H ± would lead to certain tension with flavor physics bounds (mainly B physics, see [27] for a review). We emphasize that the mass ranges selected for our numerical scan are quite conservative since lower values for m H , m A and m H ± are allowed by LHC data, see e.g.…”

Measurements of branching fractions of leptonic and hadronic $ D_s^{+} $ meson decays and extraction of the $ D_s^{+} $ meson decay constant

“…In some NP scenarios, the leptonic decay rates of the D + s mesons could also be modified although the expected effects are smaller than in the B meson sector [6][7][8][9]. Measurements of leptonic decays of charmed hadrons, D + s → + ν where + = e + , µ + or τ + , therefore enable precision tests of LQCD calculations of decay constants performed in the charm sector and can provide additional constraints on NP.…”

$$\mu \rightarrow e \gamma $$ μ → e γ in the 2HDM: an exercise in EFT

“…The decay μ → eγ has been extensively studied in the 2HDM [3,[15][16][17][18][19][20][21][22][23][24][25][26][27], particularily in connection [29][30][31][32][33][34][35][36][37] with the recent LHC [28,38] excess in h → τ ± μ ∓ . Chang, Hou and Keung [5] (CHK) calculate the contributions to μ → eγ of neutral Higgs bosons with flavour-changing couplings.…”