Vector Leptoquarks Could Be Rather Light?

Abstract

Some low-energy manifestations of a minimal extension of the Standard Model based on the quark-lepton $SU(4{)}_V\otimes SU(2{)}_L\otimes G_R$ symmetry of the Pati-Salam type are analysed. Given this symmetry a new type of mixing in the quark-lepton interactions is shown to be required. An additional arbitrariness of the mixing parameters could allow to decrease noticeably the lower bound on the leptoquark mass $M_X$ originated from the $\pi$ and $K$ decays and the $\mu e$ conversion. The only mixing independent bound emerging from the cosmological limit on the ${\pi }^0\to \nu \bar{\nu }$ decay width is $M_X>18TeV$.

Comments: 10 pages, LaTeX, Yaroslavl, Yaroslavl State University preprint YARU-HE-94/02