Vector leptoquark mass limits and branching ratios of $ K_L^0, B^0, B_s \to l^+_i l^-_j $ decays with account of fermion mixing in leptoquark currents

TL;DR

This paper calculates vector leptoquark mass limits and predicts branching ratios for certain meson decays, considering fermion mixing, and finds results close to current experimental data, guiding future searches.

Contribution

It introduces a comprehensive calculation of vector leptoquark effects on meson decay branching ratios, including fermion mixing, and establishes a lower mass limit of 86 TeV.

Findings

Lower vector leptoquark mass limit: 86 TeV

Predicted branching ratios for B decays are close to experimental data

Some decay modes have branching ratios 2-4 times below current limits

Abstract

The contributions of the vector leptoquarks of Pati-Salam type to the branching ratios of $K_L^0, B^0, B_s \to l \, l^{\prime}$ decays are calculated with account of the fermion mixing in the leptoguark currents of the general type. Using the general parametrizations of the mixing matrices the lower vector leptoquark mass limit $ m_V > 86 \,\, TeV $ is found from the current experimental data on these decays. The branching ratios of the decays $B^0, B_s \to l \, l^{\prime}$ predicted at $m_V = 86 \,\, TeV$ are calculated. These branching ratios for the decays $ B^0, B_s \to \mu^+ \mu^-, e \mu $ are close to the experimental data whereas those for the decays $B^0 \to e^+ e^-, e \tau, \mu \tau$, and $B_s \to e^+ e^-$ are by order of $2\div4$ less than their current experimental limits. For the decays $B_s \to e \tau, \mu \tau$ these branching ratios are of order $10^{-10}$ and $10^{-9}$ respectively. The predicted branching ratios will be usefull in the current and future experimental searches for these decays.