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

TL;DR

This paper calculates mass limits and decay branching ratios for chiral gauge leptoquarks based on fermion mixing and experimental data, providing predictions relevant for future experimental searches.

Contribution

It introduces a comprehensive analysis of chiral gauge leptoquark effects on meson decay branching ratios considering general fermion mixing matrices.

Findings

Lower mass limit for $V^{L}$ leptoquarks is 5.68 TeV with certain assumptions.

Predicted branching ratios for some decays can approach current experimental limits.

Decays involving tau leptons could have branching ratios around 10^{-7}.

Abstract

The contributions of the chiral gauge leptoquarks $V^{L,R}$ induced by the chiral four color quark-lepton symmetry to the branching ratios of $ K_L^0, B^0, B_s \to l_1 \, l_2 $ decays are calculated and analysed using the general parametrizations of the fermion mixing matrices in the leptoguark currents. From the current experimental data on these decays under assumption $ m_{V^L} \ll m_{V^R} $ the lower mass limit $ m_{V^L} \cos{\gamma_L} > 5.68 \,\, \mbox{TeV}$ is found, which in particular case of equal gauge coupling constants gives $ m_{V^L} > 8.03 \,\, \mbox{TeV} $. The branching ratios of the decays under consideration predicted by the chiral gauge leptoquarks are calculated and analysed in dependence on the leptoquark masses and the mixing parameters. It is shown that in consistency with the current experimental data these branching ratios for $ B_s, B^0 \to \mu e $ decays can be close to their experimental limits and those for $ B_s, B^0 \to \tau e, \tau \mu $ decays can be of order of~$10^{-7}$. The calculated branching ratios will be useful in the further experimental searches for these decays.