Phi meson production cross sections in pion-baryon and baryon-baryon interactions

Abstract

Phi meson production in pion-baryon and baryon-baryon interactions near the production threshold is studied in a boson-exchange model. Parameters in this model are either taken from the Bonn model for the nucleon-nucleon potential or determined from the measured phi meson decay width and the experimental data for the reactions π − p→φn and pp→ppφ. The isospinaveraged cross sections for the reactions πN →φN , π∆→φN , N N →N N φ, which are needed in transport models to study phi meson production in heavyion collisions at subthreshold energies, have been evaluated. For the reactions N ∆→N N φ and ∆∆→N N φ, which become singular when the exchanged pion is on-shell, the Peierls method is used to calculate their cross sections. We find that the cross section for the reaction πN →φN is much larger than the other cross sections.

Polarization observables in the reactionNN→NNφ

“…Our cut-off parameter in set I is greater then the one found in ref. [2] because we use energy-suppressed coupling constants and we have a negative interference between vector and tensor parts in the pnρ vertex which is intimately related to the definition of the Lagrangian eq. (2).…”

“…First, the elementary total cross section [1,2] is an important input for the calculation of the Φ production in heavy-ion collisions [3]. In this case one might expect some change of the Φ width [4] due to the coupling to the decay channel Φ → K + K − and peculiarities according to the in-medium modification of the kaon properties [5,6].…”

Production of φ mesons in near-threshold π

“…The early theoretical studies [8,9] show, indeed, that predictions for hadronic observables are very sensitive to the parameters of the monopole form factors which can not be fixed unambiguously without adjustments relying on the corresponding experimental data. In our case one can rely on the recent measurement of the ratio of the total cross sections of φ and ω production in pp reactions studied by the DISTO Collaboration at SATURNE at T lab = 2.85 GeV as well as on the φ angular distribution in the pp → ppφ reaction [10] and on the total cross section [11].…”

Seeing phi mesons through dileptons

“…In Ref. [40], we have studied phi meson production from heavy-ion collisions at these energies through its KK decay channel. Comparison of the phi meson yield from the transport model with the preliminary data from the FOPI collaboration [39] seems to indicate that medium effects on phi meson play a non-negligible role.…”

“…The present work is a continuation of Ref. [40]. Our main motivation is to examine the feasibility of detecting directly the reduction of phi meson mass in nuclear medium from the dilepton invariant mass spectrum from heavy ion collisions, which will be measured by HADES in the near future [16].…”