Extending our study of the vector meson-nucleon scattering lengths, we are focusing on the $\rho$-meson case using recent CLAS threshold data for the reaction $\gamma p\to \rho p$ within the meson–baryon reaction model. The total ${\sigma }_t(\gamma p\to \rho p)$ and ${\sigma }_t(\gamma p\to \omega p)$ cross sections are close to the momentum of the vector meson in CM $q=0.2\mathrm{GeV}/\mathrm{c}$. Then the $\rho p$ photoproduction cross section grows rapidly. Our result for $\rho N$ scattering length is a factor of 4 smaller than the size of the hadron and the phenomenological determination of the $\omega$ nucleon scattering length using threshold photoproduction cross sections. The observed difference between $\rho N$ and $\omega N$ scattering lengths is of interest for further understanding within hadron structure theory.

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• Phenomenology