Double ϕ production in p¯p reactions near threshold

We employ an effective Lagrangian approach to investigate double ϕ production in the p¯p reaction near the threshold and describe a notable violation of the Okubo-Zweig-Iizuka (OZI) rule in this reaction process through hadronic degrees of freedom, using the currently available theoretical and experimental information. The ground-state nucleon and its s-wave resonances, i.e., N^⁎(1535,1650,1895), are taken into account in the t- and u-channel tree-level diagrams. The pentaquark-like nucleon resonance P_s(2071,3/2⁻) is also considered. In the s-channel diagrams, scalar and tensor mesons are incorporated, specifically f₀(2020,2100,2200) and f₂(1950,2010,2150), respectively, along with the pseudoscalar meson η(2225). Our calculations suggest that contributions from the N and N^⁎ resonances significantly enhance the cross-section near the threshold. At the same time, those from the f₀ and f₂ mesons produce distinctive peak structures around W=2.2 GeV, qualitatively reproducing the JETSET experimental data. The openings of the Λ¯Λ and Σ¯Σ channels lead to the cusp structures, which can explain the nontrivial structures in the cross-section at W≈2M_Λ and 2M_Σ observed in the data. It turns out that contributions from the η and P_s resonances are almost negligible. Additionally, polarization observables such as the spin density matrix element (SDME) provide crucial insights into the individual hadronic processes involved in this reaction.