1. A probe for hot & dense nuclear matter. Lake Louise Winter Institute 21 February, 2000 Manuel Calderón de la Barca Sánchez

2. 2Lake Louise Winter Institute 21 February, 2000 Heavy Ions & QGP Aims to probe nuclear matter at high energy densities Goal is to study the predicted transition from ordinary nuclear matter to quark matter, and to actually create such a state of freely interacting quarks & gluons. –Can we understand nuclear physics with quark degrees of freedom?

3. 3Lake Louise Winter Institute 21 February, 2000 Heavy Ion Collisions: Background Specific to RHIC –Tunable Energy  30 - 200 GeV for Au-Au –Changeable species : p  Pb

4. 4Lake Louise Winter Institute 21 February, 2000 Physics of Heavy Ion Spectra at RHIC Particle production increases significantly –~800-2000 charged particles per unit rapidity Hard scattering is prominent P t distributions allows access to observables related to –temperature –baryo- and strangeness chemical potential –energy flow

5. 5Lake Louise Winter Institute 21 February, 2000 Insight into collision dynamics Slopes –Deviations äHigh-pt, parton MS & energy loss äjet quenching? P t Distributions

6. 6Lake Louise Winter Institute 21 February, 2000 RHIC Collisions: Environment TPCy Pions (~80%) Kaons Protons

7. 7Lake Louise Winter Institute 21 February, 2000 Hard Scattering High pt particles –jets & single particles calculable in pQCD –allows access to small distances, early times äaffected by the dense medium? –dE/dx energy loss  softening of p t spectrum äretain information about the collision –fast particles  little to no rescattering in hadronic stage –should be significant in number äexpect ~50% of Et to be produced via partonic processes

8. 8Lake Louise Winter Institute 21 February, 2000 STAR Detector TPC acceptance –/  / < 1.5, 0 <  < 2  B z = 0.5 T Particle ID via –dE/dx –RICH

9. 9Lake Louise Winter Institute 21 February, 2000 Inside the STAR TPC

10. 10Lake Louise Winter Institute 21 February, 2000 Tracking Resolution: –1.5% @ 1GeV/c for , K, p

11. 11Lake Louise Winter Institute 21 February, 2000 dE/dx : Truncated Mean p(GeV/c)

12. 12Lake Louise Winter Institute 21 February, 2000 RICH Particle ID Pions Kaons Protons  = 450 MeV/c K = 675 MeV/c p = 840 MeV/c To 5 GeV/c RICH PID p t (GeV/c)

13. 13Lake Louise Winter Institute 21 February, 2000 RHIC Year-1 Data May - August, 10 weeks ~ 10 6 evts Central Collision Rates: 100 Hz (12 Mb data/evt) Goals –y and p t distributions for charged tracks. äCan we do a rough characterization of the collision? –As possible, obtain spectra for specific particles separately using PID information. äWill there be differences btw different particle species? –Particle distributions vs. multiplicity.

14. 14Lake Louise Winter Institute 21 February, 2000 Multiplicity & Centrality Study particle distributions as a function of Nch Compare to p-p data Look for deviations from predicted behavior

15. 15Lake Louise Winter Institute 21 February, 2000 High-Pt Studies Single Particle Inclusive Spectra (h +, h - ) Future studies –Particle Ratios at high p t äp bar /p compared to p+p, insight into jet quenching? äRICH can identify protons up to 5 GeV/c –J/  Spectra äPredicted to be suppressed in QGP äL3 Trigger + EM Calorimeter for e + e -

16. 16Lake Louise Winter Institute 21 February, 2000 Summary STAR: Ready in May TPC, RICH for high-pt Spectra physics. Analyses over full impact parameter range out to several GeV/c in p t –Sensitive to fundamental event characteristics – Will there be surprises?