Abstract
We update the standard model (SM) predictions of R(D*) using the latest results on the decay distributions in B → D∗ℓνℓ (ℓ = μ, e) by Belle collaboration, while extracting |Vcb| at the same time. Depending on the inputs used in the analysis, we define various fit scenarios. Although the central values of the predicted R(D*) in all the scenarios have reduced from its earlier predictions in 2017, the results are consistent with each other within the uncertainties. In this analysis, our prediction of R(D*) is consistent with the respective world average at ∼ 3σ. We have also predicted several angular observables associated with B → D*τντ decays. We note that the predicted FL(D*) is consistent with the corresponding measurement at 2σ. Utilizing these new results, we fit the Wilson coefficients appearing beyond the standard model of particle physics (BSM). To see the trend of SM predictions, we have used the recently published preliminary results on the form-factors at non-zero recoil by the lattice groups like Fermilab-MILC and JLQCD and predicted the observables in B → D∗ℓνℓ, and B → D*τντ decays.
Highlights
Method of predicting R(D∗) which will be relatively less sensitive to the inputs from heavy quark effective theory (HQET) is essential, and lattice inputs on the form-factors at non-zero recoil are required for that
We fit the Wilson coefficients appearing beyond the standard model of particle physics (BSM)
As we find that this Bayesian fit is highly insensitive to the BGL coefficient aF2 2, we have set aF2 2 = 0 without any loss of generality in making the predictions of the B → D∗τ ντ observables
Summary
There are two form-factors f+(z) and f0(z) relevant for B → D ν decays, while those for B → D∗ ν decays are given by f (z), g(z), F1(z) and F2(z), respectively. Other relevant inputs like the quark masses (mb, mc), αS and ΛQCD are taken from the reference [13] We use these eight synthetic data-points to perform a Bayesian fit to the sub-leading Isgur-Wise functions. In an attempt to obtain a conservative estimate of the form factor F2, we fit the BGL parameters aF0 2 and aF2 2 to the above-generated synthetic data-points. [15]) is highly constrained by the lattice data from MILC we can safely use the MILC data in estimating aF0 2 Using this conservative estimate of aF0 2 together with the fit results for the BGL B → D∗ ν form-factor coefficients for N = 2, we have estimated R(D∗), Pτ (D∗), FL(D∗), and AF B(D∗), which are tabulated in table 6. The results obtained using Belle 2017 data differ from these new results, as seen before
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