title: Two-photon decay of the neutral pion in lattice QCD.
abstract: We perform a nonperturbative calculation of the π(0) → γγ transition form factor and the associated decay width using lattice QCD. The amplitude for a two-photon final state, which is not an eigenstate of QCD, is extracted through a Euclidean time integral of the relevant three-point function. We utilize the all-to-all quark propagator technique to carry out this integration 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 a possible discretization effect, we obtain Γπ(0) → γγ = 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.
authors.affiliation: High Energy Accelerator Research Organization, KEK, Tsukuba 305-0801, Japan.
authors.forename: Xu
authors.initials: X
authors.lastname: Feng
authors.forename: Sinya
authors.initials: S
authors.lastname: Aoki
authors.forename: Hidenori
authors.initials: H
authors.lastname: Fukaya
authors.forename: Shoji
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Kaneko
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Noaki
authors.forename: Eigo
authors.initials: E
authors.lastname: Shintani