Decoding the Proton’s Response to an External Electromagnetic Field

The proton is the only composite building block of matter that is stable in nature, making its properties key to understanding the formation of matter. A team of physicists measured the proton’s electric polarizability, which characterizes the proton’s susceptibility to deformation, or its “stretchability,” in the presence of a photon’s electromagnetic field. The results reveal a puzzling new structure – a bump in the polarizability that nuclear theory cannot explain.