Calculation of the pion charge radius from an improved model-independent method

TL;DR

This paper introduces an improved, model-independent method for calculating the pion charge radius that reduces systematic errors, validated on mockup and lattice QCD data.

Contribution

The authors develop a modified method that minimizes systematic errors in pion charge radius calculations, especially for small pole mass and volume, improving upon previous approaches.

Findings

Method successfully applied to mockup data

Method validated with lattice QCD data at 0.51 GeV pion mass

Reduces systematic errors in charge radius calculation

Abstract

We propose a new improved model-independent method for calculating the pion charge radius. In a recently-proposed model-independent method for the pion charge radius, we find it difficult to compute the pion charge radius for small pole mass $M_{\rm{pole}}^2$ and volume due to systematic errors coming from finite volume effect and higher-order contamination of the Taylor expansion of the form factor. We circumvent this difficulty by introducing a new appropriate function and propose a modified method that can calculate the pion charge radius with less systematic errors in the small $M_{\rm{pole}}^2$ and volume cases. As preliminary results, we check that our improved model-independent method works well on a mockup data and also an actual lattice QCD data at the pion mass of 0.51 GeV.