Updates on SM predictions of $|V_{cb}|$ and $R(D^{\ast })$ in $B\to D^{\ast }\ell {\nu }_{\ell }$ decays

Abstract

We update the standard model (SM) predictions of $R(D^{\ast })$ using the latest results on the decay distributions in $B\to D^{\ast }\ell {\nu }_{\ell }$ ($\ell =\mu ,e$) by Belle collaboration, while extracting $|V_{cb}|$ at the same time. Depending on the inputs used in the analysis, we define various fit scenarios. Although the central values of the predicted $R(D^{\ast })$ 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 $R(D^{\ast })$ is consistent with the respective world average at $\sim 3\sigma$. We have also predicted several angular observables associated with $B\to D^{\ast }\tau {\nu }_{\tau }$ decays. We note that the predicted $F_L(D^{\ast })$ is consistent with the corresponding measurement at 2$\sigma$. 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 utilized 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 $B\to D^{\ast }\ell {\nu }_{\ell }$, and $B\to D^{\ast }\tau {\nu }_{\tau }$ decays.

Comments: 28 pages, 9 captioned figures, Version accepted in JHEP