Light-cone sum rules for proton decay

TL;DR

This paper uses light-cone sum rules to estimate form factors for proton-to-pion transitions relevant to proton decay, providing results consistent with lattice QCD and paving the way for more complex decay channel analyses.

Contribution

It introduces a novel application of light-cone sum rules to calculate proton decay form factors in a kinematic regime extrapolated to decay conditions.

Findings

Form factors agree with lattice QCD within uncertainties

Method applicable to more complex decay channels

Provides estimates in a previously unexplored kinematic regime

Abstract

We estimate the form factors that parametrise the hadronic matrix elements of proton-to-pion transitions with the help of light-cone sum rules. These form factors are relevant for semi-leptonic proton decay channels induced by baryon-number violating dimension-six operators, as typically studied in the context of grand unified theories. We calculate the form factors in a kinematical regime where the momentum transfer from the proton to the pion is space-like and extrapolate our final results to the regime that is relevant for proton decay. In this way, we obtain estimates for the form factors that show agreement with the state-of-the-art calculations in lattice QCD, if systematic uncertainties are taken into account. Our work is a first step towards calculating more involved proton decay channels where lattice QCD results are not available at present.