Non-perturbative proton stability

TL;DR

This paper presents a non-perturbative calculation showing that QCD effects exponentially suppress proton decay rates, which could significantly alter constraints on grand unified theories.

Contribution

The authors introduce a non-perturbative approach within the chiral bag model revealing exponential suppression of proton decay matrix elements due to QCD effects.

Findings

Exponential suppression of proton decay matrix elements by non-perturbative QCD

Suppression is significant for small quark masses and chiral symmetry breaking

Potentially rescues certain GUT models from current decay constraints

Abstract

Proton decay is a generic prediction of GUT models and is therefore an important channel to detect the existence of unification or to set limits on GUT models. Current bounds on the proton lifetime are around 10^33 years, which sets stringent limits on the GUT scale. These limits are obtained under `reasonable' assumptions about the size of the hadronic matrix elements. In this paper we present a non-perturbative calculation of the hadronic matrix elements within the chiral bag model of the proton. We argue that there is an exponential suppression of the matrix elements, due to non-perturbative QCD, that stifles proton decay by orders of magnitude -- potentially O(10^-10). This suppression is present for small quark masses and is due to the chiral symmetry breaking of QCD. Such a suppression has clear implications for GUT models and could resuscitate several scenarios.