Pion generalized parton distribution from lattice QCD

We present the first lattice calculation of the valence-quark generalized parton distribution (GPD) of the pion using the large-momentum effective theory (LaMET) approach. We focus on the zero-skewness limit, where the GPD has a probability-density interpretation in the longitudinal Bjorken x and the transverse impact-parameter distributions. Our calculation is done using clover valence fermions on an ensemble of gauge configurations with 2 + 1 + 1 flavors (degenerate up/down, strange and charm) of highly improved staggered quarks (HISQ) with lattice spacing a ≈ 0.12 fm, box size L ≈ 3 fm and pion mass m_π ≈ 310 MeV. The parton distribution function and the form factor are reproduced as special limits of the GPD as expected. Due to the large errors, this exploratory study does not show a clear preference among different model assumptions about the kinematic dependence of the GPD. To discriminate between these assumptions, future studies using higher-statistics data will be crucial.