On energy densities reached in heavy-ion collisions at the CERN SPS

Abstract

We present a few estimates of energy densities reached in heavyion collisions at the CERN SPS. The estimates are based on data and models of proton-nucleus and nucleus-nucleus interactions. In all of these estimates the maximum energy density in central Pb+Pb interactions is larger than the critical energy density ε c ≈ 0.7 GeV/fm 3 following from lattice gauge theory computations. In estimates which we consider as realistic the maximum energy density is about 2ε c . In this way our analysis gives some support to claims that deconfined matter has been produced at the CERN SPS. Any definite statement requires a deeper understanding of formation times of partons and hadrons in nuclear collisions. We also compare our results with implicit energy estimates contained in earlier models of anomalous J/ψ suppression in nuclear collisions.

Cosmological Consequences of QCD Phase Transition(s) in Early Universe

“…Although the energy density ǫ available to heavy ion experiments at CERN-SPS [3], BNL-RHIC [4] and recently to CERN-LHC [5] exceeds the critical value calculated in lattice QCD (ǫ c ≈ 2 GeV/fm −3 for physical quark masses and vanishing net baryon number density), there is no unambiguous QGP-signature. For example, ǫ achieved at RHIC ∼ 5.5 GeV/fm 3 for proper time τ 0 ∼ 1 fm/c.…”

Black Box QGP

“…Although the energy density available in heavy-ion collisions at CERN-SPS [2] and now at BNL-RHIC [3] exceeds the critical value calculated in lattice QCD (ǫ c ≈ 0.7 GeV/fm −3 ), many physicists still debate on QGP signatures under these laboratory conditions. If T c = T f o should hold at small chemical potentials, phenomenological signals that characterize phase transition should remain measurable in the final state.…”