Flavor Twisted Boundary Conditions and Isovector Form Factors

TL;DR

This paper introduces flavor twisted boundary conditions in lattice QCD to compute isovector form factors at continuous momentum transfer, addressing finite volume effects with chiral perturbation theory.

Contribution

It demonstrates how flavor twisted boundary conditions can be used to calculate isovector form factors at arbitrary momenta and assesses finite volume effects on these calculations.

Findings

Twisted boundary conditions enable continuous momentum transfer calculations.

Finite volume effects significantly impact the extraction of isovector moments.

Chiral perturbation theory helps quantify volume effects in lattice simulations.

Abstract

We use vector flavor symmetry to relate form factors of isospin changing operators to isovector form factors. Flavor twisted boundary conditions in lattice QCD thus allow isovector form factors of twist-two operators, e.g, to be computed at continuous values of the momentum transfer. These twisted boundary conditions, moreover, are implemented only in the valence sector. Effects of the finite volume must be addressed to extract isovector moments and radii at zero lattice momentum. As an example, we use chiral perturbation theory to assess the volume effects in extracting the isovector magnetic moment of the nucleon from simulations with twisted boundary conditions.