a probe for hot & dense nuclear matter. lake louise winter institute 21 february, 2000 manuel...
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A probe for hot & dense nuclear matter.
Lake Louise Winter Institute 21 February, 2000
Manuel Calderón de la Barca Sánchez
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?
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Heavy Ion Collisions: Background
• Specific to RHIC– Tunable Energy 30 - 200 GeV for Au-Au– Changeable species : p Pb
AGS SPS RHIC
snn4.8 GeV 17 GeV 200 GeV
Mode Fixed Target Fixed Target Collider
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Physics of Heavy Ion Spectra at RHIC
• Particle production increases significantly– ~800-2000 charged
particles per unit rapidity
• Hard scattering is prominent
• Pt distributions allows access to observables related to– temperature
– baryo- and strangeness chemical potential
– energy flow
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• Insight into collision dynamics
• Slopes
– DeviationsHigh-pt, parton
MS & energy lossjet quenching?
Pt Distributions
T
p
edpp
dN
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RHIC Collisions: Environment
TPC y
•Pions (~80%)
•Kaons
•Protons
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Hard Scattering
• High pt particles – jets & single particles calculable in pQCD– allows access to small distances, early times
affected by the dense medium?– dE/dx energy loss softening of pt spectrum
retain information about the collision– fast particles little to no rescattering in hadronic stage
– should be significant in numberexpect ~50% of Et to be produced via partonic
processes
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STAR Detector
• TPC acceptance
– // < 1.5, 0 < < 2
• Bz = 0.5 T
• Particle ID via
– dE/dx
– RICH
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Tracking
• Resolution:
– 1.5% @ 1GeV/c for , K, p
pp
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RICH Particle ID
•Pions•Kaons•Protons
<pt>
= 450 MeV/c
K = 675 MeV/c
p = 840 MeV/c
To 5 GeV/c
RICH PID
RICH PID
pt(GeV/c)
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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.
Can we do a rough characterization of the collision?
– As possible, obtain spectra for specific particles separately using PID information.Will there be differences btw different particle species?
– Particle distributions vs. multiplicity.
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Multiplicity & Centrality
• Study particle distributions as a function of Nch
• Compare to p-p data• Look for deviations
from predicted behavior
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High-Pt Studies
• Single Particle Inclusive Spectra (h+, h-)
• Future studies– Particle Ratios at high pt
pbar/p compared to p+p, insight into jet quenching?
RICH can identify protons up to 5 GeV/c
– J/ Spectra Predicted to be suppressed in QGPL3 Trigger + EM Calorimeter for e+e-
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