Speaker
Description
We investigate the $\phi N$ reaction using an effective Lagrangian model combined with Reggeized $\rho$ and $b_1$ exchanges in the $t$-channel. The strong $\phi N N^*$ coupling leads us to include the nucleon, several $N^*$ resonances, and a hidden-strangeness state $P_s$ in the $s$- and $u$-channels. The Regge approach follows the same procedure as in the $K^+ p \rightarrow K^{*0} n$ reaction. The total and forward-angle differential cross sections show a threshold enhancement due to sub-threshold $N^*$ states. A discrepancy around $E_{\text{c.m.}} \approx 2.15$ GeV is resolved by introducing a new resonance, $N^*(2150)$, with fitted couplings. Its inclusion improves agreement with the data. We further test $N^*(2150)$ in $\phi N$ photoproduction using the same parameters. For $J^P = 3/2^+$, the result supports the possible existence of this resonance. The $d\sigma/dt$ distribution shows a dip near $-t \approx 0.5~\text{GeV}^2$, reproduced only with Regge contributions. To describe this, an imaginary term is added to the Regge trajectory: $\alpha_\rho(t) = 0.55 + 0.8t + i0.1$. This helps to control the dip structure and confirms the significance of Regge effects in this reaction.
