Nucleon decay in a minimal non-SUSY GUT with predicted quark-lepton Yukawa ratios

TL;DR

This paper explores nucleon decay predictions in a minimal non-SUSY SU(5) GUT model with specific Yukawa ratio predictions, extending the model with additional Higgs and fermion representations, and uses MCMC analysis to compare with experimental data.

Contribution

It introduces a minimal non-SUSY SU(5) GUT model with specific Yukawa ratios and analyzes nucleon decay signatures to distinguish flavor structures using MCMC methods.

Findings

Predicted Yukawa ratios of 3/2 and 9/2 for tau/b and mu/s within the model.

Nucleon decay rate ratios can serve as fingerprints to differentiate GUT models.

Model viability is supported by fitting low-scale quark and lepton masses with neutrino mass mechanisms.

Abstract

We investigate the predictions for various nucleon decay rates and their ratios in non-supersymmetric SU(5) Grand Unified Theories (GUTs) where the masses of the third and second family down-type quarks and charged leptons each stem dominantly from single GUT operators. Extending the Georgi-Glashow SU(5) model by a 45-dimensional GUT-Higgs representation, the gauge couplings can meet at the high scale $M_\mathrm{GUT}$ and the GUT scale predictions $y_\tau/y_b = 3/2$ and $y_\mu/y_s = 9/2$ can emerge within single operator dominance. Explaining the observed neutrino masses via the type I seesaw mechanism by adding SU(5) singlet fermion representations and taking their renormalization group effects into account, we show that these predictions can lead to viable low scale second and third family down-type quark and charged lepton masses. To investigate nucleon decay predictions, we extend the minimal scenario to two "toy models" towards explaining quark and lepton masses and mixings with different flavor structure, and perform Markov Chain Monte Carlo (MCMC) analyses confronting the models with the available experimental data. We show that if several nucleon decay channels are observed, the ratios between their partial decay rates can serve as "fingerprints", allowing to separate between GUT models with different flavor structure.