Virtual Compton scattering measurements in the nucleon resonance region

We report on new measurements of the electric Generalized Polarizability (GP) of the proton in a kinematic region where a puzzling dependence on momentum transfer has been observed, and we have found that =(5.3±0.6±1.3)10−4 fm3 at 2=0.20 (GeV/c)2. The new measurements, when considered along with the rest of the world data, suggest that can be described by either a local plateau or by an enhancement in the region 2=0.20 (GeV/c)2 to 0.33 (GeV/c)2. The experiment also provides the first measurement of the Coulomb quadrupole amplitude in the →Δ transition through the exploration of the (,′) reaction. The new measurement gives =(−4.4±0.8±0.6)% at 2=0.20 (GeV/c)2 and is consistent with the results from the pion electroproduction world data. It has been obtained using a completely different extraction method, and therefore represents a strong validation test of the world data model uncertainties.