The production of ρ, ω and Φ vector-mesons by protons and sulphur ions with incident momentum of 200 GeV/c per nucleon

The production of ρ, ω and Φ vector-mesons, detected through their μμ decay channel, is studied in p-W, S-S, S-Cu and S-U reactions at 200 GeV/c per nucleon incident momentum. Their inclusive cross-sections are determined in various transverse momentum intervals and their dependence on the projectile and target mass numbers is investigated. The relative yield BμμσΦ/(B_μμΦ_ρ+Bμμσω) is measured, both as a function of the transverse momentum, pT, and of the collision centrality. While this ratio exhibits no significant dependence with pT, it clearly increases with the centrality of the collision. Effective temperatures deduced from the transverse mass spectra, dσ/dM_T, lead to values of T_ρ+ω equal or slightly higher than TΦ. Both these effective temperatures smoothly increase from p-W to S-U reactions.