New Physics in Rare B Decays after Moriond 2021

TL;DR

This paper updates the global analysis of rare B decay anomalies with new experimental data, highlighting persistent deviations from the Standard Model and proposing specific new physics scenarios consistent with recent measurements.

Contribution

It provides an updated global fit of Wilson coefficients incorporating latest experimental results and improved theoretical uncertainties, offering new physics interpretations of B decay anomalies.

Findings

Muon-specific Wilson coefficients C9 and C10 fit data well.

Certain Wilson coefficient values improve fit over Standard Model by over 4.6 sigma.

Predictions for lepton flavor universality and CP asymmetries are provided for future tests.

Abstract

The anomalies in rare $B$ decays endure. We present results of an updated global analysis that takes into account the latest experimental input -- in particular the recent results on $R_K$ and BR$(B_s \to \mu^+\mu^-)$ -- and that qualitatively improves the treatment of theory uncertainties. Fit results are presented for the Wilson coefficients of four-fermion contact interactions. We find that muon specific Wilson coefficients $C_9 \simeq -0.73$ or $C_9 = -C_{10} \simeq -0.39$ continue to give an excellent description of the data. If only theoretically clean observables are considered, muon specific $C_{10} \simeq 0.60$ or $C_9=-C_{10} \simeq -0.35$ improve over the Standard Model by $\sqrt{\Delta \chi^2} \simeq 4.7\sigma$ and $\sqrt{\Delta \chi^2} \simeq 4.6\sigma$, respectively. In various new physics scenarios we provide predictions for lepton flavor universality observables and CP asymmetries that can be tested with more data. We update our previous combination of ATLAS, CMS, and LHCb data on BR$(B_s \to \mu^+\mu^-)$ and BR$(B^0\to \mu^+\mu^-)$ taking into account the full two-dimensional non-Gaussian experimental likelihoods.