ar X iv : h ep - p h / 01 02 02 0 v 1 2 F eb 2 00 1 1 Explosive Collisions at RHIC ?

Many new results have poured forth from RHIC ( √ s = 130A GeV). Several appear to be qualitatively different from those at the SPS ( √ s = 17A GeV). “Dynamical” fluctuations in the average transverse momentum, pt, are almost three times larger than at the SPS [1]. Observed HBT radii are small, ∼ 5−7 fm [2], and average transverse boost velocities are large, ∼ .6 c [3]. In particular, that the HBT radii Rout/Rside ≤ 1, as a function of pion pair pt : 200 → 400 MeV, suggests “explosive” behavior [2]. Lastly, suppression of particles at high pt : 2 → 6 GeV appears to be a clear diagnostic probe [4,5]. Based upon a condensate model [6], previously we predicted dynamical fluctuations in the average transverse momentum [7]. Using known features of the condensate model [7], here we suggest how it might produce explosive behavior at the QCD phase transition, and affect the suppression of particles at high pt. At infinitely high temperature, by asymptotic freedom QCD is an ideal gas of massless quarks and gluons. Lattice data [8] and effective theories [9] suggest that from infinite temperature, on down to perhaps twice the transition temperature, Tc, it really is a plasma: a nearly ideal gas of quarks and gluons, augmented with “thermal” masses. For temperatures of 2Tc down to Tc, instead of quasiparticles, it is more useful to think of a condensate [6]. In a nonabelian gauge theory without quarks, the order parameter for the deconfining phase transition is the Polyakov loop, l. This is the trace of the SU(3) color Aharanov-Bohm phase factor in the imaginary time direction. By asymptotic freedom, the expectation value of l, 〈l〉 = l0, is one at infinite temperature; from ’t Hooft, it is zero in the confined phase, T < Tc. Thus in going from 2Tc down to Tc, the condensate for the Polyakov loop evaporates. In the condensate model, the pressure is determined by a potential for l [6], with