# Continuing search for new physics in $b \to s \mu \mu$ decays: two operators at a time

## TL;DR

This paper investigates new physics contributions to specific effective operators in $b o s \mu\mu$ decays, analyzing scenarios with two operators at a time to explain observed anomalies and updating fits with recent data.

## Contribution

It performs a comprehensive global fit to $b o s$ data considering pairs of operators, identifying the most favored new physics scenarios in light of recent measurements.

## Key findings

- Scenarios with ($C_9^{
m NP}$, $C_9^\prime$) or ($C_9^{
m NP}$, $C_{10}^\prime$) are most favored.
- The ($C_9^{
m NP}$, $C_{10}^{
m NP}$) scenario's attractiveness diminishes with new data.
- Movement of $R_K$ towards unity could revive the $C_9^{
m NP} = -C_9^\prime$ scenario.

## Abstract

The anomalies in the measurements of observables involving $b \to s \mu\mu$ decays, namely $R_K$, $R_{K^*}$, $P_5^{\prime}$, and $B_s^\phi$, may be addressed by adding lepton-universality-violating new physics contributions to the effective operators ${\cal O}_9, {\cal O}_{10}, {\cal O}^\prime_9, {\cal O}^\prime_{10}$. We analyze all the scenarios where the new physics contributes to a pair of these operators at a time. We perform a global fit to all relevant data in the $b \to s$ sector to estimate the corresponding new Wilson coefficients, $C_9^{\rm NP}, C_{10}^{\rm NP}, C_9^\prime, C_{10}^\prime$. In the light of the new data on $R_K$ and $R_{K^*}$ presented in Moriond 2019, we find that the scenarios with new physics contributions to the ($C_9^{\rm NP}$, $C_9^\prime$) or ($C_9^{\rm NP}$, $C_{10}^\prime$) pair remain the most favored ones. On the other hand, though the competing scenario ($C_9^{\rm NP}$, $C_{10}^{\rm NP}$) remains attractive, its advantage above the SM reduces significantly due to the tension that emerges between the $R_K$ and $R_{K^*}$ measurements with the new data. The movement of the $R_K$ measurement towards unity would also result in the re-emergence of the one-parameter scenario $C_9^{\rm NP} = -C_9^\prime$.