TY - JOUR

T1 - The πγ → ππ transition and the ρ radiative decay width from lattice QCD

AU - Alexandrou, Constantia

AU - Leskovec, Luka

AU - Meinel, Stefan

AU - Negele, John

AU - Paul, Srijit

AU - Petschlies, Marcus

AU - Pochinsky, Andrew

AU - Rendon, Gumaro

AU - Syritsyn, Sergey

N1 - Publisher Copyright:
Copyright © 2018, The Authors. All rights reserved.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2018/7/22

Y1 - 2018/7/22

N2 - We report a lattice QCD determination of the πγ → ππ transition amplitude for the P-wave, I = 1 two-pion final state, as a function of the photon virtuality and ππ invariant mass. The calculation was performed with 2 + 1 flavors of clover fermions at a pion mass of approximately 320 MeV, on a 323 × 96 lattice with L ≈ 3.6 fm. We construct the necessary correlation functions using a combination of smeared forward, sequential and stochastic propagators, and determine the finite-volume matrix elements for all ππ momenta up to |P~| = √32Lπ and all associated irreducible representations. In the mapping of the finite-volume to infinite-volume matrix elements using the Lellouch-Lüscher factor, we consider two different parametrizations of the ππ scattering phase shift. We fit the q2 and s dependence of the infinite-volume transition amplitude in a model-independent way using series expansions, and compare multiple different truncations of this series. Through analytic continuation to the ρ resonance pole, we also determine the πγ → ρ resonant transition form factor and the ρ meson photocoupling, and obtain |Gρπγ| = 0.0802(32)(20).

AB - We report a lattice QCD determination of the πγ → ππ transition amplitude for the P-wave, I = 1 two-pion final state, as a function of the photon virtuality and ππ invariant mass. The calculation was performed with 2 + 1 flavors of clover fermions at a pion mass of approximately 320 MeV, on a 323 × 96 lattice with L ≈ 3.6 fm. We construct the necessary correlation functions using a combination of smeared forward, sequential and stochastic propagators, and determine the finite-volume matrix elements for all ππ momenta up to |P~| = √32Lπ and all associated irreducible representations. In the mapping of the finite-volume to infinite-volume matrix elements using the Lellouch-Lüscher factor, we consider two different parametrizations of the ππ scattering phase shift. We fit the q2 and s dependence of the infinite-volume transition amplitude in a model-independent way using series expansions, and compare multiple different truncations of this series. Through analytic continuation to the ρ resonance pole, we also determine the πγ → ρ resonant transition form factor and the ρ meson photocoupling, and obtain |Gρπγ| = 0.0802(32)(20).

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M3 - Article

AN - SCOPUS:85095141181

JO - Nuclear Physics A

JF - Nuclear Physics A

SN - 0375-9474

ER -