ELFT HÍRADÓ

[Levai Peter <plevai AT rmki.kfki.hu>]

  KFKI RMKI Elmeleti Foosztaly Szeminariuma


 Tisztelettel megh?vjuk

             Prof. Brian A. Cole
         Columbia University, New York

      "Unraveling the High-pT Puzzle at RHIC"

         c?mmel tartand? szemin?riumara.

     Helye: KFKI RMKI III. ?p. Tan?csterem
     Ideje: 2003. Marcius 14.  Pentek du 12.45 ?ra


Szivesen latunk minden erdeklodot.

                                  Levai Peter

Az eloadas rovid kivonata:

Experimental data from experiments at the Relativistic Heavy Ion
Collider (RHIC) at Brookhaven National Laboratory have convincingly
demonstrated a deficit in the production of particles at large
transverse momentum (pT) in ultra-relativistic Au-Au collisions
compared to expectations based on perturbative quantum chromodynamics
(pQCD). Such a "suppression" in the production of large pT
particles was predicted to result from final-state radiative
energy loss of hard-scattered partons in the surrounding dense, hot
matter created in the early stages of a heavy ion collision. If
radiative energy loss is indeed responsible for the suppression of
high-pT hadron production, then we have for the first time
unambiguously observed the effects of the true strong force
acting in bulk matter. In addition, the magnitude of the suppression
would provide, in principle, direct sensitivity to properties of this
matter, However, it has been argued by others that high-pT
suppression could result from modification of the gluon distribution
in ultra-relativistic nuclei due to longitudinal coherence of the
gluons in the nuclear wave function. The same authors have argued that
the same coherence could also produce an observable suppression in
proton-nucleus or deuteron-nucleus collisions. RHIC is now nearing
the completion of a 10+ week d-Au run at a nucleon-nucleon center of
mass energy Sqrt{s} = 200 GeV and the results from this run should
unambiguously determine whether gluon saturation significantly
modifies high-pT particle production at RHIC.

I will present a summary of the experimental data on
high-pT suppression, focusing on results from the PHENIX
experiment and will show comparisons of the data to radiative
energy loss and gluon saturation calculations. I will discuss
other uncertainties in the interpretation of the data and
highlight alternative experimental observables that may
improve our understanding of the high-pT suppression.
I will finish with a status report on the d-Au run and
a discussion of what PHENIX hopes to measure using the acquired
d-Au data.