Neutrino magnetic moment induced by leptoquarks

Abstract

Allowing leptoquarks to interact with both right-handed and left-handed neutrinos (i.e., ``nonchiral'' leptoquarks), we show that a nonzero neutrino magnetic moment can arise naturally. Although the mass of the nonchiral vector leptoquark that couples to the first generation fermions is constrained severely by universality of the ${\ensuremath{\pi}}^{+}$ leptonic decays and is found to be greater than 50 TeV, the masses of the second and third generation nonchiral vector leptoquarks may evade such constraint and may in general be in the range of $1--100 \mathrm{TeV}$. With reasonable input mass and coupling values, we find that the neutrino magnetic moment due to the second generation leptoquarks is of the order of ${10}^{\ensuremath{-}12}--{10}^{\ensuremath{-}15}{\ensuremath{\mu}}_{\mathrm{B}},$ while that caused by the third generation leptoquarks, being enhanced significantly by the large top quark mass, is in the range of ${10}^{\ensuremath{-}10}--{10}^{\ensuremath{-}13}{\ensuremath{\mu}}_{\mathrm{B}}.$