Lepton flavour violating B meson decays via scalar leptoquark

TL;DR

This paper investigates how scalar leptoquarks could enhance lepton flavour violating B meson decays, predicting observable branching ratios at current and future experiments, and constrains the model using existing decay limits.

Contribution

It provides the first detailed analysis of scalar leptoquark effects on LFV B meson decays, with predictions within experimental reach and updated parameter constraints.

Findings

Predicted LFV B decay branching ratios are within experimental reach.

Constrained leptoquark parameter space using current decay limits.

Analyzed rare kaon decays in the leptoquark framework.

Abstract

We study the effect of scalar leptoquarks in the lepton flavour violating $B$ meson decays induced by the flavour changing transitions $b \to q l_i^+ l_j^-$ with $q=s,d$. In the standard model these transitions are extremely rare as they are either two-loop suppressed or proceed via box diagrams with tiny neutrino masses in the loop. However, in the leptoquark model they can occur at tree level and are expected to have significantly large branching ratios. The leptoquark parameter space is constrained using the experimental limits on the branching ratios of $B_q \rightarrow l^+ l^-$ processes. Using such constrained parameter space, we predict the branching ratios of LFV semileptonic $B$ meson decays, such as $B^+ \to K^+ (\pi^+) l_i^+ l_j^-$, $B^+ \to (K^{* +}, \rho^+) l_i^+ l_j^-$ and $B_s \to \phi l_i^+ l_j^-$, which are found to be within the experimental reach of LHCb and the upcoming Belle II experiments. We also investigate the rare leptonic $K_{L, S} \to \mu^+ \mu^- (e^+ e^-)$ and $K_{L} \to \mu^\mp e^\pm$ decays in the leptoquark model.