Proton lifetime bounds from chirally symmetric lattice QCD

TL;DR

This paper calculates matrix elements relevant for proton decay in GUTs using lattice QCD with domain wall fermions, providing crucial inputs to constrain GUT models based on experimental proton lifetime bounds.

Contribution

It offers the first lattice QCD determination of proton decay matrix elements using chirally symmetric fermions, improving the precision of GUT constraints.

Findings

Low energy constants  and  determined with uncertainties.

Matrix elements related to proton decay estimated at a fixed lattice spacing.

Results enable tighter bounds on GUT parameters from proton lifetime data.

Abstract

We present results for the matrix elements relevant for proton decay in Grand Unified Theories (GUTs). The calculation is performed at a fixed lattice spacing a^{-1}=1.73(3) GeV using 2+1 flavors of domain wall fermions on lattices of size 16^3\times32 and 24^3\times64 with a fifth dimension of length 16. We use the indirect method which relies on an effective field theory description of proton decay, where we need to estimate the low energy constants, \alpha = -0.0112(25) GeV^3 and \beta = 0.0120(26) GeV^3. We relate these low energy constants to the proton decay matrix elements using leading order chiral perturbation theory. These can then be combined with experimental bounds on the proton lifetime to bound parameters of individual GUTs.