Deep Exclusive Electroproduction of π0 at High Q2 in the Quark Valence Regime

We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of x_B (0.36, 0.48, and 0.60) and Q² (3.1 to 8.4 GeV² ) obtained from Jefferson Lab Hall A experiment E12-06-014. The corresponding structure functions d σ_T/d t +ε d σ_L/d t , d σ_{T T}/d t , d σ_{L T}/d t , and d σ_{L T^'}/d t are extracted as a function of the proton momentum transfer t -t_min. The results suggest the amplitude for transversely polarized virtual photons continues to dominate the cross section throughout this kinematic range. The data are well described by calculations based on transversity generalized parton distributions coupled to a helicity flip distribution amplitude of the pion, thus providing a unique way to probe the structure of the nucleon.