Flavor structure of GUTs and uncertainties in proton lifetime estimates

Abstract

We study the flavor aspects of proton lifetime estimates in simple grand-unified models, paying particular attention to their inherent fragility due to the notorious lack of control of some of the key parameters governing the relevant hard-process amplitudes. Among these, the theoretical uncertainties in the flavor structure of the baryon-and lepton-number-violating charged currents due to the potential higher-order effects afflicting the matching of the underlying Yukawa couplings to the low-energy data often play a prominent role. Focusing on the minimal variants of the most popular unified models, we study the potential instabilities of the corresponding proton lifetime estimates based on the renormalizable-level Yukawa fits with respect to the Planck-scale-induced flavor effects. In particular, we perform a detailed numerical analysis of all minimal SO(10) Yukawa sector fits available in the literature and show that the proton lifetime estimates based on these inputs exhibit a high degree of robustness with respect to moderate-size perturbations, well within the expected "improvement window" of the upcoming proton decay searches.