While this measurement may give a hint of QGP formation, a definite conclusion has to await for clearer measurements. The nuclear absorption effect is reasonably well understood. The combinatoric background is a major concern for such studies. NA50 Collaboration T. Matsui and H. Satz, Phys.
OZI rule states that reactions involving disconnected quark lines are forbidden.
In heavy ion collisions, strangeness production is enhanced due to particle rescattering and perhaps QGP formation. The approximate chiral symmetry is simultaneously broken. The chiral symmetry is approximate because of the non-vanishing but small u, d quark current masses. The argument for the similar inverse slopes is that phi-mesons and protons participate in the transverse flow motion and freeze out at similar conditions. Therefore, it is important to measure the transverse spectra to address the question to what degree the phi-mesons participate in collective flow.