a sample calculation on a $64^4$ lattice with the quark masses close to the physical point, which suggests that form factor calculations at the physical point become feasible by enlarging lattice sizes to $M_\pi L\approx 4$.'
author:
- |
    Oanh Hoang Nguyen$^{a}$, Ken-Ichi Ishikawa$^{b}$, Akira Ukawa$^{a,c}$, Naoya Ukita$^{c}$\
    for PACS-CS Collaboration
title: ' Electromagnetic form factor of pion from $N_f=2+1$ dynamical flavor QCD '
---

UT-CCS-60\

Introduction
============

The electromagnetic form factor of pion is an interesting quantity to investigate in lattice QCD. Experimentally it has been measured in a set of experiments [@pdg]. Together with the nucleon form factors, it provides the first important test case of our understanding of hadron structure that arises from the quark content. From lattice QCD point of view, form factor calculations represent one of the first steps going beyond static quantities like the mass spectrum which require only two-point functions. The pion form factor is a natural first choice in this direction since usually pion Green’s functions are statistically the most stable quantities in lattice QCD measurements. An interesting point with the pion form factor $G_\pi(q^2)$ is its slope at the origin as a function of the momentum transfer squared $q^2$, [*i.e.,*]{} the 