Pion structure from twisted mass lattice QCD down to the physical pion mass

Abstract

We present an investigation of pion structure based on ETMC $N_f=2$ and $N_f=2+1+1$ twisted mass configurations at maximal twist. We compute the first moment of the quark momentum fraction of the pion, $\langle x \rangle$ and the electromagnetic form factor, $F_\pi(Q^2)$. For the latter, momentum is injected using twisted boundary conditions and the calculation is carried out directly at the physical pion mass. We find that our data are consistent with vector meson dominance and experimental data in the region of small momentum transfer. For $\langle x \rangle$, we find that our chirally and continuum extrapolated result is compatible with its phenomenological value.