New Insight in the Q2 Dependence of Proton Generalized Polarizabilities

Abstract

© 2019 American Physical Society. Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer Q2: 0.10, 0.20, and 0.45 GeV2, at the Mainz Microtron. Fits performed using either the low-energy theorem or dispersion relations allowed the extraction of the structure functions PLL-PTT/ϵ and PLT, as well as the electric and magnetic generalized polarizabilities αE1(Q2) and βM1(Q2). These new results show a smooth and rapid falloff of αE1(Q2), in contrast to previous measurements at Q2=0.33 GeV2, and provide for the first time a precise mapping of βM1(Q2) in the low-Q2 region.