It has been shown recently that the anomalies observed inB → D ( * ) τν τ andB →K + − decays could be resolved with just one scalar leptoquark. Fitting to the current data on R(D ( * ) ) along with acceptable q 2 distributions inB → D ( * ) τν τ decays, four best-fit solutions for the operator coefficients have been found. In this paper, we explore the possibilities of how to discriminate these four solutions. Firstly, we find that two of them * With the discovery of heavy quark spin-flavor symmetry and the formulation of heavy quark effective theory (HQET) [1][2][3][4][5], it has become clear that the physical observables in semi-leptonic B → D ( * ) ν could be rather reliably predicted within the Standard Model (SM), especially at the zero recoil point, allowing therefore a reliable determination of the Cabibbo-Kobayashi-Maskawa (CKM) element V cb . It is also believed that the effect of New Physics (NP) beyond the SM should be tiny since these decays are induced by the tree-level charged current.However, the BaBar [6, 7], Belle [8,9] and LHCb [10] collaborations have recently observed anomalies in the ratios R(D ( * ) ) = B(B → D ( * ) τν τ ) B(B → D ( * ) ν ) , = e/µ . (1.1) The Heavy Flavor Average Group (HFAG) gives the average values [11] R(D) avg =0.397 ± 0.040 ± 0.028 , R(D * ) avg =0.316 ± 0.016 ± 0.010 , (1.2) which exceed the SM predictions [12, 13] R(D) SM =0.300 ± 0.008 , R(D * ) SM =0.252 ± 0.003 , (1.3) by 1.9σ and 3.3σ, respectively. Especially when the R(D)-R(D * ) correlation of −0.21 is taken into account, the tension with the SM predictions would be at 4.0σ level [11]. Theoretically, R(D) and R(D * ) can be rather reliably calculated, because they are independent of the CKM element |V cb | and, to a large extent, of the B → D ( * ) transition form factors.The above anomalies have been investigated extensively both within model-independent frameworks [14-35], as well as in some specific NP models where the b → cτν τ transition is mediated by leptoquarks [14, 15, 36-44], charged Higgses [14, 45-55], charged vector bosons [14, 56-58], and sparticles [ [59][60][61]. It is also interesting to point out that, besides the branching ratios, the measured differential distributions dΓ(B → D ( * ) τν)/dq 2 by BaBar [7] and Belle [8,9]

Given that the two-Higgs-doublet model of type III (2HDM-III) has the potential to address the R D (*) anomalies while the resolution to the R K (*) deficits requires new degrees of freedom within this framework, we consider in this paper a unified scenario where the low-scale type-I seesaw mechanism is embedded into the 2HDM-III, so as to accommodate the R D (*) and R K (*) anomalies as well as the neutrino mass. We first revisit the R D (*) anomalies and find that the current world-averaged results can be addressed at 2σ level without violating the bound from the branching ratio B(B − c → τ −ν) 30%. The scenario predicts two sub-eV neutrino masses based on a decoupled heavy Majorana neutrino and two nearly degenerate Majorana neutrinos with mass around the electroweak scale. For the R K (*) anomalies, the same scenario can generate the required Wilson coefficients in the direction C NP 9µ = −C NP 10µ < 0, with O(1) Yukawa couplings for the muon and the top quark.

In this paper, we perform a complete one-loop computation of the short-distance Wilson data. We find that the Manohar-Wise model could explain the current data, especially when the couplings of the charged colour-octet scalars to quarks are complex, with the resulting χ 2 min being significantly smaller than that of the SM. Finally, we investigate correlations among the two isospin asymmetries ∆(K * γ) and ∆(ργ), as well as the averaged time-integrated branching ratios B(B s,d → µ + µ − ); some of them are found to be quite strong and could provide, therefore, further insights into the model, once more precise experimental measurements and theoretical predictions for these observables are available in the future.

This work aims to explore the 2.8σ discrepancy observed between the BaBar measurement and the Standard Model prediction of the CP asymmetry in τ → K S πν τ decays. Firstly, we reproduce the known CP asymmetry due to K 0 −K 0 mixing by means of the reciprocal basis, which is convenient when a K S(L) is involved in the final state. As the Kπ tensor form factor plays a crucial role in generating an extra direct CP asymmetry that can arise only from the interference of vector and tensor operators, we then present a dispersive representation of this form factor, with its phase obtained in the context of chiral theory with resonances, which fulfills the requirements of unitarity and analyticity. Finally, the τ → K S πν τ decays are analyzed both within a model-independent low-energy effective theory framework and in a scalar leptoquark scenario. It is observed that the CP anomaly can be accommodated in the model-independent framework, even at the 1σ level, together with the constraint from the branching ratio of this decay; it can be, however, marginally reconciled only at the 2σ level, due to the specific relation between the scalar and tensor operators in the scalar leptoquark scenario.

No abstract