Flavor Phenomenology of the Leptoquark Singlet-Triplet Model

TL;DR

This paper proposes a combined scalar leptoquark model to simultaneously explain anomalies in B decays and muon magnetic moment, providing a comprehensive analysis of its phenomenological implications and future test predictions.

Contribution

It introduces a novel model combining singlet and triplet scalar leptoquarks to address multiple flavor anomalies simultaneously.

Findings

The combined model can explain all three anomalies without conflicting with other measurements.

Identifies benchmark points with specific predictions for future experiments.

Analyzes correlations among different flavor observables.

Abstract

In recent years, experiments revealed intriguing hints for new physics (NP) in semi-leptonic $B$ decays. Both in charged current processes, involving $b \to c \tau \nu$ transitions, and in the neutral currents $b\to s\ell^+\ell^-$, a preference for NP compared to the standard model (SM) of more that $3\sigma$ and $5\sigma$ was found, respectively. In addition, there is the long-standing tension between the theory prediction and the measurement of the anomalous magnetic moment (AMM) of the muon ($a_\mu$) of more than $3\sigma$. Since all these observables are related to the violation of lepton flavor universality (LFU), a common NP explanation seems not only plausible but is even desirable. In this context, leptoquarks (LQs) are especially promising since they give tree-level effects in semi-leptonic $B$ decays, but only loop-suppressed effects in other flavor observables that agree well with their SM predictions. Furthermore, LQs can lead to a $m_t/m_\mu$ enhanced effect in $a_{\mu}$, allowing for an explanation even with (multi) TeV particles. However, a single scalar LQ representation cannot provide a common solution to all three anomalies. In this article we therefore consider a model in which we combine two scalar LQs: the $SU(2)_L$ singlet and the $SU(2)_L$ triplet. Within this model we compute all relevant one-loop effects and perform a comprehensive phenomenological analysis, pointing out various interesting correlations among the observables. Furthermore, we identify benchmark points which are in fact able to explain all three anomalies ($b \to c \tau \nu$, $b\to s\ell^+\ell^-$ and $a_\mu$), without violating bounds from other observables, and study their predictions for future measurements.