Double $\phi$-meson production via $\bar{p}p$ scattering

Abstract

We investigate double $\phi$ production in $\bar{p}p$ reactions near threshold using an effective Lagrangian approach, highlighting a significant OZI rule violation through hadronic processes. Our model includes $t$- and $u$-channel contributions from the nucleon and $s$-wave $N^*$ resonances ($N^*(1535,1650,1895)$), as well as the pentaquark-like state $P_s(2071)$. In the $s$-channel, scalar ($f_0$), tensor ($f_2$), and pseudoscalar ($\eta(2225)$) mesons are incorporated. The $N$, $N^*$, $f_0$, and $f_2$ contributions enhance the cross-section and generate peak structures near $W=2.2$ GeV, consistent with JETSET data, while cusp structures arise from $\bar{\Lambda}\Lambda$ and $\bar{\Sigma}\Sigma$ threshold openings. Polarization observables, such as the spin density matrix element (SDME), further elucidate the underlying hadronic mechanisms.