Nucleon distribution amplitudes and proton decay matrix elements on the lattice

TL;DR

This paper computes moments of the nucleon distribution amplitude using lattice QCD, providing insights into proton decay matrix elements and challenging previous assumptions about the DA's deviation from its asymptotic form.

Contribution

It presents the first lattice QCD calculation of the first few moments of the nucleon DA and normalizes twist-four DAs relevant for proton decay in GUTs.

Findings

Deviation of the nucleon DA from asymptotic form is less pronounced than previously claimed.

Provides nonperturbative renormalization of relevant operators in MSbar scheme.

Uses gauge configurations with two flavors of clover fermions.

Abstract

Baryon distribution amplitudes (DAs) are crucial for the theory of hard exclusive reactions. We present a calculation of the first few moments of the leading-twist nucleon DA within lattice QCD. In addition we deal with the normalization of the next-to-leading (twist-four) DAs. The matrix elements determining the latter quantities are also responsible for proton decay in Grand Unified Theories. Our lattice evaluation makes use of gauge field configurations generated with two flavors of clover fermions. The relevant operators are renormalized nonperturbatively with the final results given in the MSbar scheme. We find that the deviation of the leading-twist nucleon DA from its asymptotic form is less pronounced than sometimes claimed in the literature.