Phenomenology of scalar leptoquarks

TL;DR

This paper investigates minimal scalar leptoquark models, focusing on their phenomenology, proton decay constraints, and the implications of higher-dimensional operators for baryon number violation.

Contribution

It identifies two minimal scalar leptoquark models free from proton decay at the renormalizable level and analyzes their phenomenological implications, including rare decay enhancements.

Findings

One model shows an unusual top mass enhancement of mu -> e gamma decay.

Dimension five operators can cause baryon number violation unless forbidden by symmetries.

Both models are constrained by existing and future experimental data.

Abstract

We study the simplest renormalizable scalar leptoquark models where the standard model is augmented only by one additional scalar representation of SU(3) x SU(2) x U(1). The requirement that there be no proton decay from renormalizable interactions singles out two such models, one of which exhibits an unusual top mass enhancement of the mu -> e gamma decay rate. We analyze the phenomenology of the model with the unusual top mass enhancement of loop level chirality changing charged lepton processes in the light of existing and upcoming experiments. Both of the models that do not allow proton decay from renormalizable interactions have dimension five operators that, even if suppressed by the Planck scale, can give rise to an unacceptably high level of baryon number violation. We discuss symmetries that can forbid these dimension five operators.