We study all possible observables in B → D ( * ) τ ντ with new physics (NP), including new vector, scalar and tensor interactions, and investigate the prospects of extracting NP Wilson coefficients with optimal observables. Analysis of the full q 2 integrated branching fractions of B → D ( * ) τ ντ show that the overall sensitivity of the observables of B → Dτ ντ is more towards the scalar current, whereas the bin-by-bin analysis of q 2 distribution of the differential branching fraction points to regions of q 2 sensitive to tensor interactions. Interestingly, the observables in B → D * τ ντ are more sensitive to tensor interactions, and bin-by-bin analysis of this mode shows the distinct regions of q 2 sensitive to vector or scalar interactions. In addition to that, the τ polarisation asymmetry is found to be more sensitive to NP compared to the other observables, in both decay modes.

We study the decays B → D ( * ) τ ντ in light of the available data from BABAR, Belle and LHCb. We divide our analysis into two parts: in one part we fit the form-factors in these decays directly from the data without adding any additional new physics (NP) contributions and compare our fit results with those available from the decays B → D ( * ) ν . We find that the q 2 -distributions of the formfactors associated with the pseudo-vector current, obtained from B → D ( * ) τ ντ and B → D ( * ) ν respectively, do not agree with each other, whereas the other form-factors are consistent with each other. In the next part of our analysis, we look for possible new effective operators of dimension 6 amongst new vector, scalar, and tensor-type that can best explain the current data in the decays B → D ( * ) τ ντ . We use the information-theoretic approaches, especially of 'Second-order Akaike Information Criterion' (AICc) in the analysis of empirical data. Normality tests for the distribution of residuals are done after selecting the best possible scenarios, for cross-validation. We find that it is the contribution from the operator involving left or right-handed vector current that passes all the selection criteria defined for the best-fit scenario and can successfully accommodate all the available data set.

In this article, we predict the standard model (SM) values of the asymmetric and angular observables in B → D (*) τ ν τ decays, using the results of the new up-todate analysis in B → D (*) ν. We also revisit the SM prediction of the inclusive ratio R X c , and we give its values in different schemes of the charm quark mass. This is the first analysis which includes all the known corrections in the SM. In addition, we analyze the b → cτ ν τ decay modes in a model-independent framework of effective field theory beyond the standard model. Considering all the possible combinations of the effective operators in b → cτ ν τ decays and using the Akaike information criterion, we find the scenarios which can best explain the available data on these channels. In the selected scenarios, best-fit values and correlations of the new parameters are extracted. Using these results, predictions are made on various observables in the exclusive and inclusive semitaunic b → c decays. The graphical correlations between these observables are shown, which are found to be useful in discriminating various new physics scenarios.

In the light of recent data, we study the new physics effects in the exclusive b → s + − decays from a model independent perspective. Different combinations of the dimension six effective operators along with their respective Wilson coefficients are chosen for the analysis. To find out the operator or sets of operators that can best explain the available data in this channel, we simultaneously apply popular model selection tools like cross-validation and the information theoretic approach like Akaike Information Criterion (AIC). There are one, two, and three-operator scenarios which survive the test and a left-handed quark current with vector muon coupling is common among them. This is also the only surviving one-operator scenario. Best-fit values and correlations of the new Wilson coefficients are supplied for all the selected scenarios. We find that the angular observables play the dominant role in the model selection procedure. We also note that while a left-handed quark current with axial-vector muon coupling is the only one-operator scenario able to explain the ratios R K ( * ) (RK * for q 2 ∈ [0.045, 1.1]GeV 2 in particular), there are also a couple of two operator scenarios that can simultaneously explain the measured R K ( * ) .

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