The third type of fermion mixing in the lepton and quark interactions with leptoquarks

TL;DR

This paper explores a minimal extension of the Standard Model with quark-lepton symmetry, revealing a third mixing type in leptoquark interactions that could relax existing mass bounds from rare processes.

Contribution

It introduces a new third type of mixing in leptoquark interactions within a Pati--Salam inspired model, impacting bounds on leptoquark masses.

Findings

Third mixing type is necessary for leptoquark interactions.

Additional mixing parameters could lower leptoquark mass bounds.

Potential to explain low-energy rare process observations.

Abstract

The low-energy manifestations of a minimal extension of the electroweak standard model based on the quark-lepton symmetry $SU(4)_V \otimes SU(2)_L \otimes G_R$ of the Pati--Salam type are analyzed. Given this symmetry the third type of mixing in the interactions of the $SU(4)_V$ leptoquarks with quarks and leptons is shown to be required. An additional arbitrariness of the mixing parameters could allow, in principle, to decrease noticeably the lower bound on the vector leptoquark mass originated from the low-energy rare processes, strongly suppressed in the standard model.