Role of $\sigma$ exchange in the $\gamma p\to \phi p$ process and   scaling with the $f_1$ axial vector meson from a Reggeized model
  We investigate the role driven by the scalar meson $\sigma$ exchange in the photoproduction of the vector meson $\phi$(1020) off a proton by using a Reggeized model. Based on the $\pi^0(135)+\sigma(500)+f_2(1270)$+Pomeron exchanges, we demonstrate that the $\sigma$ exchange plays the role to reproduce the bump structure at the forward angle in the differential cross section as well as the peaking behavior in the total cross section observed in the CLAS Collaboration. We also discuss the possible observation of the scaled cross section $s^7d\sigma /dt$ at the production angle $\theta=90^{\circ}$ from the CLAS data. It is found that the axial vector meson $f_1(1285)$ exchange with the trajectory $\alpha_{f_1}(t)=0.028\,t+0.9\pm0.2$ arising from the axial anomaly of the QCD vacuum plays the role to clarify the scaling up to 5 GeV. 
Byung-Geel Yu, Hungchong Kim and Kook-Jin Kong
hep-ph nucl-th