First extraction of the proton mass radius and scattering length $$\vert\alpha_{\rho^{0}p}\vert$$ from ρ0 photoproduction

As it involves the lightest physical states excited from vacuum by vector quark current, near-threshold ρ0 photoproduction is considered a possible way to research proton radius and absolute value of scattering lengths ρ0-proton interaction. In this study, under assumption scalar form factor dipole form, mass calculated as (0.85 ± 0.06) fm fitting differential cross section γp → ρ0p reaction at energy. For light meson photoproduction, because exchange quark-antiquark pair not suppressed should dominate gluon exchange, we extract likely represent proton. This fact may explain why obtained in study very near charge radius. Moreover, length $$\vert\alpha_{\rho^{0}p}\vert=(0.31 \pm 0.06)$$ for first time within dominance model. result disobeys rule that $$\vert\alpha_{V_{p}}\vert$$ increases with meson’s mass, which can be attributed treating point analysis. These results provide useful theoretical information an in-depth understanding structure proton-vector