Speaker
Description
We investigate the hadronic production of the $\phi$ meson in the OZI-suppressed reaction $\pi^- p \to \phi n$ near threshold within an effective Lagrangian framework. Since the $\phi$ meson is predominantly an $s\bar{s}$ state, its direct coupling to the nucleon is expected to be strongly suppressed at the quark level. However, intermediate hadronic channels and baryon resonances can generate sizable $\phi N$ interactions, making this reaction an ideal probe of the underlying reaction mechanism, the $\phi N$ interaction, and possible hidden-strangeness pentaquark states.
The reaction amplitude is constructed from the $s$-, $u$-, and $t$-channel diagrams with nucleon, $N^*$ resonance, and meson-exchange contributions. The model satisfies the extended Ward-Takahashi identity within the hidden local symmetry framework, and Reggeized propagators are introduced to describe the reaction at moderately high energies.
Our preliminary results indicate that the $N^*$ resonances play an important role in reproducing the observed near-threshold behavior, while the $t$-channel contribution becomes increasingly significant at higher energies. In addition to the total and differential cross sections, we investigate the spin-density matrix elements (SDMEs) of the produced $\phi$ meson in the helicity and Gottfried-Jackson frames. These polarization observables provide complementary information for identifying the underlying reaction mechanisms beyond cross-section measurements. The remaining discrepancies in the forward-angle region suggest that further investigation of the $t$-channel contributions and comparison with more precise experimental data will be necessary.
