# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1905.08253