A probe for hot dense nuclear matter Lake

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

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? Lake Louise Winter Institute 21 February, 2000 2

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

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

Pt Distributions • Insight into collision dynamics • Slopes – Deviations ä High-pt, parton MS & energy loss ä jet quenching? Lake Louise Winter Institute 21 February, 2000 5

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

Hard Scattering • High pt particles – jets & single particles calculable in p. QCD – allows access to small distances, early times äaffected by the dense medium? – d. E/dx energy loss softening of pt 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 Lake Louise Winter Institute 21 February, 2000 7

STAR Detector • TPC acceptance – / / < 1. 5, 0 < < 2 • Bz = 0. 5 T • Particle ID via – d. E/dx – RICH Lake Louise Winter Institute 21 February, 2000 8

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

Tracking • Resolution: – 1. 5% @ 1 Ge. V/c for , K, p Lake Louise Winter Institute 21 February, 2000 10

d. E/dx : Truncated Mean Lake Louise Winter Institute 21 February, 2000 p(Ge. V/c) 11

RICH Particle ID <pt> RICH PID • Pions • Kaons • Protons Lake Louise Winter Institute 21 February, 2000 RICH PID = 450 Me. V/c K = 675 Me. V/c p = 840 Me. V/c To 5 Ge. V/c pt(Ge. V/c) 12

RHIC Year-1 Data • May - August, 10 weeks ~ 106 evts • Central Collision Rates: 100 Hz (12 Mb data/evt) • Goals – y and pt 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. Lake Louise Winter Institute 21 February, 2000 13

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

High-Pt Studies • Single Particle Inclusive Spectra (h+, h-) • Future studies – Particle Ratios at high pt äpbar/p compared to p+p, insight into jet quenching? äRICH can identify protons up to 5 Ge. V/c – J/ Spectra äPredicted to be suppressed in QGP äL 3 Trigger + EM Calorimeter for e+e. Lake Louise Winter Institute 21 February, 2000 15

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