Photon and $\pi^0$ electroproduction in Jlab Hall A (6 GeV experiements)

Abstract

Generalized Parton Distribution (GPDs) are universal functions which provide a comprehensive description of hadron properties in terms of quarks and gluons. GPDs can be accessed experimentally with hard exclusive processes such as Deeply Virtual Compton Scattering (DVCS) and deeply virtual $\pi^0$ production. Two experiments were performed in the Hall A of Jefferson Lab to measure the unpolarized cross sections of these two processes off the proton and off the neutron in the valence region ($x_B$=0,36) at $Q^2\approx$2 GeV$^2$. After a brief description of the experimental setup, the DVCS off the proton results will be discussed and interpreted as being unexpectedly sensitive to gluons. Then, the longitudinal/transverse separation of the $\pi^0$ electoproduction cross sections, showing a dominance of the transverse terms, will be presented. Finally, an estimation of the quarks up and down contributions to the $\pi^0$ electroproduction cross sections, by combining the proton and the neutron measurements, will be shown.