Addendum to "Impact of polarization observables and $B_c\to \tau \nu$ on new physics explanations of the $b\to c \tau \nu$ anomaly"

TL;DR

This paper updates the analysis of the $b o c au u$ anomaly by incorporating recent experimental measurements, refining theoretical predictions, and examining collider constraints to better understand potential new physics explanations.

Contribution

It provides updated fit results and predictions for observables related to the $b o c au u$ anomaly, including new collider constraints and theoretical insights on fragmentation functions.

Findings

Updated ${ m R}(D)$ and ${ m R}(D^*)$ measurements show a 3.1 sigma tension with the Standard Model.

New fit results and collider constraints refine the parameter space for new physics models.

Predicted ${ m R}(\Lambda_c)$ aligns with the Standard Model within uncertainties.

Abstract

In this addendum to arXiv:1811.09603 we update our results including the recent measurement of ${\cal R}(D)$ and ${\cal R}(D^*)$ by the Belle collaboration: ${\cal R}(D)_{\rm Belle} = 0.307\pm0.037\pm0.016$ and ${\cal R}(D^*)_{\rm Belle}=0.283\pm0.018\pm0.014$, resulting in the new HFLAV fit result ${\cal R}(D) = {0.340\pm0.027 \pm 0.013}$, ${\cal R}(D^*) = {0.295\pm0.011 \pm 0.008 }$, exhibiting a $3.1\,\sigma$ tension with the Standard Model. We present the new fit results and update all figures, including the relevant new collider constraints. The updated prediction for ${\cal R}(\Lambda_c)$ from our sum rule reads ${\cal R}(\Lambda_c)= \mathcal{R}_{\rm SM}(\Lambda_c) \left( 1.15 \pm 0.04 \right) = 0.38 \pm 0.01 \pm 0.01$. We also comment on theoretical predictions for the fragmentation function $f_c$ of $b\to B_c$ and their implication on the constraint from $B_{u/c}\to\tau\nu$ data.