Photoproductions of $f_1(1285)$ and $\eta'(958)$ from the analysis of CLAS data with the Primakoff effect at high energies

Abstract

We investigate photoproduction of axial vector meson $f_1(1285)$ based on the CLAS experiment $\gamma p\to pf_1(1285)\to p\eta\pi^+\pi^-$ using the Regge model for $\rho^0+\omega$ exchanges. The combined analysis of $\gamma p\to p\eta'\to p\eta\pi^+\pi^-$ reaction including $\eta(1295)$ is accompanied to evaluate the decay mode $\eta(1295)\to \eta\pi^+\pi^-$ from the potential overlap with the $f_1$ reaction. The predominance of $\rho^0(770)$ exchange over the $\omega(782)$ with the coupling constant $\gamma\rho^0f_1$ extracted from the CLAS experiment leads to a good description of the measured cross sections for $f_1$, while the scale of the cross section is corrected by the branching fraction $\eta'\to\eta\pi^+\pi^-$, and $f_1\to\eta\pi^+\pi^-$, respectively. As an extension to study the nonmesonic production mechanism, the Primakoff effect by the virtual photon exchange is investigated in the exclusive reaction $\gamma p\to pf_1$ up to $\sqrt{s}\approx50$ GeV, finding that it plays a similar role to the Pomeron in the vector meson photoproduction at high energies. Such an unique role of the virtual photon exchange similar to the $f_1$ case is identified up to $\sqrt{s}\approx250$ GeV in the $\gamma p\to p\pi^0$ and $\gamma p\to p\eta$ as well as $\gamma p\to p\eta'$ reaction.