Global fits to b -> s ll data and signs for lepton non-universality

TL;DR

This paper performs a comprehensive global analysis of b -> s ll decay data, revealing potential signs of lepton non-universality and discrepancies with Standard Model predictions, especially in the R_K ratio.

Contribution

It provides the first combined global fit to all b -> s ll data, highlighting possible lepton universality violation and suggesting new physics implications.

Findings

R_K ratio shows a 2.6 sigma deviation from SM

Global fits indicate potential lepton non-universality

Analysis suggests possible new physics in b -> s ll transitions

Abstract

There are some slight tensions with the SM predictions within the latest LHCb measurements. Besides the known anomaly in one angular observable of the rare decay B -> K* mu+ mu-, another small discrepancy recently occurred. The ratio R_K = BR(B+ -> K+ mu+ mu-) / BR(B+ -> K+ e+ e-) in the low-q^2 region has been measured by LHCb showing a 2.6 sigma deviation from the SM prediction. In contrast to the anomaly in the rare decay B -> K* mu+ mu- which is affected by power corrections, the ratio R_K is theoretically rather clean. We analyse all the b -> s ll data with global fits and in particular explore the possibility of breaking of lepton universality. Possible cross-checks with an analysis of the inclusive B -> X_s l+ l- decay are also explored.