Anatomy of a new anomaly in non-leptonic B decays

TL;DR

This paper analyzes a specific observable in non-leptonic B decays, finds a tension with Standard Model predictions, and explores potential new physics explanations including Wilson coefficients and extra-dimensional models.

Contribution

It introduces the $L_{VV}$ observable for B decays, identifies a tension with data, and discusses possible new physics sources and models to explain this discrepancy.

Findings

SM prediction of $L_{K^* ar{K}^*}$ is 19.5^{+9.3}_{-6.8}

Data shows a 2.6$\sigma$ tension with SM prediction

A KK gluon model can potentially explain anomalies in B decays.

Abstract

We discuss the anatomy of the $L_{VV}$ observable designed as a ratio of the longitudinal components of $B_s \to VV$ versus $B_d \to VV$ decays. We focus on the particular case of $B_{d,s} \to K^{*0} {\bar K^{*0}}$ where we find for the SM prediction $L_{K^* \bar{K}^*}=19.5^{+9.3}_{-6.8}$ implying a 2.6$\sigma$ tension with respect to data. The interpretation of this tension in a model independent way identifies two Wilson coefficients ${\cal C}_{4}$ and ${\cal C}_{8g}$ as possible sources. The example of one simplified model including a Kaluza-Klein (KK) gluon is discussed. This KK gluon embedded inside a composite/extra dimensional model combined with a $Z^\prime$ can explain also the $b\to s\ell\ell$ anomalies albeit with a significant amount of fine-tuning.