Lepton Flavour Violating tau and mu decays induced by scalar leptoquark

Abstract

We show that the scalar leptoquark Yukawa couplings generate a significant lepton flavour violation. We compute the light scalar leptoquark contributions to the branching ratios (Br) of the lepton flavour violating (LFV) decays $\ell \to {\ell }_i{\ell }_j{\bar{\ell }}_j$ and $\ell \to {\ell }^{\prime }\gamma$ with (i,j = e,$\mu$). We discuss the role of the relevant input parameters to these decay rates which are the Yukawa couplings ($h_{a\ell }$) with ($a=u,c,t$), the light scalar mass $M_{S_1}$ and the mixing angle $\sin 2{\theta }_{LQ}$. We investigate the experimental limits from $(g-2{)}_{\mu }$, $\mu -e$ conversion and $\pi \to e{\nu }_e,\mu {\nu }_{\mu }$ to get constraint on the input parameter space. We predict that the upper limits on the branching ratios of $\tau \to {\ell }_i{\ell }_j{\bar{\ell }}_j$ can reach the experimental current limits. We also show that it is possible to accommodate both $\tau \to {\ell }_i{\ell }_j{\bar{\ell }}_j$ and $\tau \to \ell \gamma$ branching ratios for certain choices of LQ parameters.