Common explanation to the RK(*) , RD

Abstract

Scalar theories can account for the current R D ( * ) measurements through a vector operatorc L γ µ b LτL γ µ ν L induced at the loop level. Once the vector contribution is considered on top of a subdominant tree-level scalar component, the predicted value of R D ( * ) falls within the 1σ region indicated by the experiments. We explicitly demonstrate this claim in the framework of a three Higgs doublet model extended with GeV scale right-handed neutrinos, by matching the anomalous signal for perturbative values of the involved couplings and respecting the bounds from complementary flavour physics measurements. Remarkably, we furthermore show that the proposed framework can be employed to simultaneously explain also the present R K ( * ) measurement, as well as the deviation in / currently being debated in the literature. These results are obtained by considering the contribution of relatively light right-handed neutrinos which are fundamental in mediating the processes behind the anomalous signals. In this way our findings reveal a new possible connection that links the flavour anomalies to the phenomenology of extended Higgs sector and neutrino physics. [18] D. Bečirević and O. Sumensari, A leptoquark model to accommodate R exp K < R SM K and R exp K * < R SM K * , JHEP 08 (2017) 104, [arXiv:1704.05835].

Generic loop effects of new scalars and fermions in b → sℓ+ℓ− and a vector-like 4th generation

“…In this context, box contributions of heavy new scalars and fermions 2 (also within multi Higgs doublet models with right-handed neutrinos [75][76][77]) have been shown to be a viable option [78][79][80][81] 3 . Furthermore, an explanation of the anomalies in b → s + − via loop effects allows for interesting connections to Dark Matter [86][87][88][89][90][91][92] and typically leads to correlated imprints on other observables like the anomalous magnetic moment of the muon (a µ ).…”

Flavour anomalies from a split dark sector

“…Possible constructions for the Wilson coefficients of the effective Hamiltonian descending from loops of TeV-scale new particles have been investigated, e.g., in refs. [39][40][41][42][43][44][45][46]. They generally involve either box diagrams of scalar and fermionic states like in figure 1(a), or penguin diagrams like the ones represented in figure 1(b).…”

b → sℓ+ℓ− transitions in two-Higgs-doublet models

“…However, contributions to other loop-induced processes such as b → sγ (for which the SM prediction [47] is in very well agreement with the experimental average [31]), b → sνν, (where the experimental upper bound [48,49] approaches the SM prediction [50]) or B s −B s mixing [31] unavoidably arise and their constraints must be taken into account. Therefore, an explanation of b → s + − data in the context of multi-Higgs-doublet models might require the introduction of right-handed neutrinos [51,52]. Furthermore, any model with sizeable couplings to muons could potentially address the long-lasting discrepancy between experiment [53] and the SM prediction 2 ∆a µ = a EXP µ − a SM µ ∼ 270(85) × 10 −11 , (1.3) of 3-4 σ.…”