Pion structure from improved lattice QCD: Form factor and charge radius at low masses

The charge form factor of the pion is calculated in lattice QCD. The nonperturbatively improved Sheikholeslami-Wohlert action is used together with the $O\left(a\right)\mathrm{}$ improved vector current. Other choices for the current are examined. The form factor is extracted for pion masses from 970 down to 360 MeV and for momentum transfers $Q^2<~2{\mathrm{GeV}}^2.$ The mean square charge radius is extracted and compared to previous determinations, and its extrapolation to lower masses discussed.