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

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 MGUT and the GUT scale predictions yτ /yb = 3/2 and yμ/ys = 9/2 can emerge within single opera-
tor 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” to-
wards 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.