Excited meson radiative transitions from lattice QCD using variationally optimized operators

TL;DR

This paper introduces a lattice QCD method using variationally optimized operators to study radiative transitions of excited mesons, enabling precise calculation of form-factors and transition amplitudes.

Contribution

It develops a novel approach combining variational analysis and distillation to accurately compute excited meson radiative transitions in lattice QCD.

Findings

Successfully computed transition form-factors for excited mesons.

Demonstrated the effectiveness of optimized operators in isolating single meson states.

Analyzed photon virtuality dependence of meson transition form-factors.

Abstract

We explore the use of optimized operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis of meson interpolating fields using a variational analysis of matrices of two-point correlation functions. After performing such a determination at both zero and non-zero momentum, we compute three-point functions and are able to study radiative transition matrix elements featuring excited state mesons. The required two- and three-point correlation functions are efficiently computed using the distillation framework in which there is a factorization between quark propagation and operator construction, allowing for a large number of meson operators of definite momentum to be considered. We illustrate the method with a calculation using anisotopic lattices having three flavors of dynamical quark all tuned to the physical strange quark mass, considering form-factors and transitions of pseudoscalar and vector meson excitations. The dependence on photon virtuality for a number of form-factors and transitions is extracted and some discussion of excited-state phenomenology is presented.