Empirical Determination of the Pion Mass Distribution

Existing pion+nucleus Drell-Yan and electron+pion scattering data are used to develop ensembles of model-independent representations the pion generalised parton distribution (GPD). Therewith, one arrives at a data-driven prediction for mass form factor, $\theta_2$. Compared with elastic electromagnetic $\theta_2$ is harder: ratio radii derived from these two factors $r_\pi^{\theta_2}/r_\pi = 0.79(3)$. Our predictions GPD, related distributions should serve as valuable constraints on theories structure.