Measurements of the proton generalized polarizabilities

The EM polarizabilities characterize a fundamental property of the proton that involves the system’s response to an external electromagnetic (EM) field. They describe how easily the charge and magnetization distributions inside the system are distorted by the EM field, such as during the Compton scattering with a real photon. When the polarizabilities are generalized to finite momentum transfer by replacing the incoming real photon of the Compton scattering process with a space-like virtual photon, they map out the deformation of the quark densities in a proton subject to an EM field. Recent experimental measurements at Jefferson Lab have provided high precision data, that offer guidance and present significant challenges to nuclear theory. Future experiments aim to improve further these measurements, both by extending their kinematic range as well as by improving the level of the experimental precision.