First extraction of the proton mass radius and scattering length $\left|{\alpha }_{{\rho }^{0}p}\right|$ from ${\rho }^0$ photoproduction

Xiao-Yun Wang, Fancong Zeng, Quanjin Wang +1

As it involves the lightest physical states excited from the vacuum by the vector quark current, near-threshold ${\rho }^0$ photoproduction is considered a possible way to research the p…