Two-photon decay of the neutral pion in lattice QCD

TL;DR

This paper presents a non-perturbative lattice QCD calculation of the neutral pion's two-photon decay width, employing advanced techniques to accurately extract the transition form factor.

Contribution

It introduces a novel lattice QCD approach using all-to-all propagators and overlap fermions to compute the c^0 to bb transition form factor and decay width.

Findings

Decay width b=7.83(31)(49) eV obtained

Method effectively includes disconnected quark diagrams

Results are consistent with experimental data

Abstract

We perform non-perturbative calculation of the \pi^0 to {\gamma}{\gamma} transition form factor and the associated decay width using lattice QCD. The amplitude for two-photon final state, which is not an eigenstate of QCD, is extracted through an Euclidean time integral of the relevant three-point function. We utilize the all-to-all quark propagator technique to carry out this integral as well as to include the disconnected quark diagram contributions. The overlap fermion formulation is employed on the lattice to ensure exact chiral symmetry on the lattice. After examining various sources of systematic effects except for possible discretization effect, we obtain \Gamma=7.83(31)(49) eV for the pion decay width, where the first error is statistical and the second is our estimate of the systematic error.