1. The Microscopic Origin of the Strangeness Enhancement at the SPS 2. The Colored Glass Condensate and Extreme QCD 3. Jet Correlation and Sca

by Stephen Vance (1) (Brookhaven National Laboratory)

Tuesday 20 Jun 2000, 09:30 → 10:00 Europe/Zurich

TH Auditorium (CERN)

1. 'The Microscopic Origin of the Strangeness Enhancement at the SPS'The microscopic origin of the strangeness enhancement observed in Pb+Pb collisions at the SPS is studied using models with different initial conditions combined with final state hadronic interactions. Using an initial condition similar to scaled p+p interactions as generated by the HIJING event generator, the inclusion of final state chemical changing processes (e.g. Lambda + K <-> Xi + pi) as modelled in the General Cascade Program (GCP) is unable to reach the observed hyperon yields. In addition, when modifying this initial condition to include baryon junction stopping and pair production mechanisms as modelled by HIJING/BBbar, the junction mechanisms and GCP chemical rates are unable to account for both the hyperon yields and the K/pi ratio. However, the addition of transient field fluctuations to HIJING/BBbar+GCP is proposed to account for the observed strangeness enhancement. The implications of these transient fields, which result from the geometrical overlap of wounded nucleons, are discussed. 2. 'The Colored Glass Condensate and Extreme QCD' The high-energy limit of QCD is controlled by the small x part of a hadron wavefunction. I argue that this part of the wavefunction is universal to all hadrons and is composed of a new form of matter: A Coloured Glass Condensate. This matter is weakly interacting at for very small x, but is non-perturbative because of the highly occupied boson states, which compose the Condensate. Such matter might be studied in high-energy lepton-hadron or hadron-hadron interactions. The high-energy limit is controlled by the density of matter in the small x wavefunction, and it is argued therefore that the best hadron for such studies is the largest possible nucleus. 3. 'Jet Correlation and Scale-Local Measures Various types of correlation analysis have been applied in the search for pQCD effects in the multihadron final state of jets. I consider some recent analyses of Delphi and H1 jet data and compare standard correlation measures with scale-local topological measures. I reinterpret the experimental results from a scale-local perspective and suggest ways to improve jet correlation analysis. I observe that scale-dependent correlation are sharply limited in these data, restricted primarily to jet width fluctuations and leading to the question where is the scale-invariant pQCD structure expected from qluon bremsstrahlung? I also consider some theoretical predictions of power-law behaviour in jet measures.

Organiser(s): Yiota Foka and Ulrich Heinz

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