Gauge and scalar boson mediated proton decay in a predictive SU(5) GUT model

Abstract

We assess proton decay signatures in the simplest viable SU(5) model with regard to constraints on parameters governing the Standard Model fermion mass spectrum. Experimental signals for all eight two-body proton decay processes result from exchange of two gauge bosons, a single scalar leptoquark, or their combination. Consequently, it enables us to delve into an in-depth anatomy of proton decay modes and anticipate future signatures. Our findings dictate that observing a proton decay into p→π0e+ indicates gauge boson mediation, with the potential for observation of p→η0e+ mode. Alternatively, if decay is through the p→K+ν¯ process, it is mediated by a scalar leptoquark, possibly allowing the observation of p→π0μ+. Detection of both p→π0e+ and p→K+ν¯ could enhance p→π0μ+ through constructive interference. The model predicts inaccessibility of p→π+ν¯, p→η0μ+, p→K0e+, and p→K0μ+, regardless of the dominant mediation type, in the coming decades. In summary, through a comprehensive analysis of proton decay signals, gauge coupling unification, and fermion masses and mixing, we both accurately and precisely constrain the parameter space of the SU(5) model in question. Published by the American Physical Society 2024