New Physics in Flavour Observables

TL;DR

Recent experimental anomalies in B-meson decays, muon magnetic moment, and lepton universality suggest potential new physics, with models involving Z' bosons and leptoquarks providing plausible explanations and testable predictions.

Contribution

This paper reviews recent anomalies and proposes leptoquark models that simultaneously address multiple deviations, predicting correlated effects in rare B decays and muon magnetic moment.

Findings

Leptoquark models can explain B decay anomalies and muon g-2.

Predicted enhancements in b→sτ+τ− processes by three orders of magnitude.

Correlated effects in b→sτμ processes are expected if multiple anomalies are explained.

Abstract

LHCb found hints for physics beyond the Standard Model (SM) in $B\to K^*\mu^+\mu^-$, $R(K)$ and $B_s\to\phi\mu^+\mu^-$. These intriguing hints for NP have recently been confirmed by the LHCb measurement of $R(K^*)$ giving a combined significance for NP above the $5\,\sigma$ level. In addition, the BABAR, BELLE and LHCb results for $B\to D^{(*)}\tau\nu$ also point towards lepton flavour universality (LFU) violating new physics (NP). Furthermore, there is the long-standing discrepancy between the measurement and the theory prediction of the anomalous magnetic moment of the muon ($a_\mu$) at the $3\,\sigma$ level. Concerning NP effects, $b\to s\mu^+\mu^-$ data can be naturally explained with a new neutral gauge bosons, i.e. a $Z^\prime$ but also with heavy new scalars and fermions contributing via box diagrams. Another promising solution to $b\to s\mu^+\mu^-$, which can also explain $B\to D^{(*)}\tau\nu$, are leptoquarks. Interestingly, leptoquarks provide also a viable explanation of $a_\mu$ which can be tested via correlated effects in $Z\to\mu^+\mu^-$ at future colliders. Considering leptoquark models, we show that an explanation of $B\to D^{(*)}\tau\nu$ predicts an enhancement of $b\to s\tau^+\tau^-$ processes by around three orders of magnitude compared to the SM. In case of a simultaneous explanation of $B\to D^{(*)}\tau\nu$ and $b\to s\mu^+\mu^-$ data, sizable effects in $b\to s\tau\mu$ processes are predicted.