Net%20Charge%20Fluctuations

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Net Charge Fluctuations in Ultra-Relativistic
Nucleus-Nucleus Collisions
Henrik Tydesjö
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OUTLINE
- The Quark Gluon Plasma - The Relativistic
Heavy Ion Collider (RHIC) The PHENIX
Experiment - QGP Signals Event-by-Event
Net-Charge Fluctuations Simulations PHENIX
Analysis
Henrik Tydesjö May 5 2004
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Phase Diagram of Nuclear Matter
Early Universe
Ultra-Relativistic Heavy-Ion Collisions ???
QGP
Hadron Gas
Neutron Stars ???
Henrik Tydesjö May 5 2004
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QUARK GLUON PLASMA
Henrik Tydesjö May 5 2004
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QUARK GLUON PLASMA
CHIRAL SYMMETRY RESTORATION
Quark Masses 0
Henrik Tydesjö May 5 2004
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Relativistic Heavy Ion Collider (RHIC)
AuAu Collisions 100 AGeV per beam
Henrik Tydesjö May 5 2004
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Collaboration
460 Members 57 Institutions 12
Countries
Henrik Tydesjö May 5 2004
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Muon Arm Spectrometers
Central Arm Spectrometers
Henrik Tydesjö May 5 2004
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Central Arms
Charged Particle Tracking Electron, Photon
Detection Hadron Identification
Pad Chambers
Henrik Tydesjö May 5 2004
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Pad Chambers

• - Multi-Wire Proportional Chambers
• - Fine Granularity Pixel Pad Readout
• - Provide Space Points for
• Track Recognition

Henrik Tydesjö May 5 2004
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Pad Chambers

• - Multi-Wire Proportional Chambers
• - Fine Granularity Pixel Pad Readout
• - Provide Space Points for
• Track Recognition

Henrik Tydesjö May 5 2004
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Event Display Central AuAu Collision
400 tracks in central arms
Henrik Tydesjö May 5 2004
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QGP SIGNALS

• Jet Quenching
• J/Y Suppression
• - Strangeness enhancement
• Thermal photon production
• Light vector meson decays
• - Fluctuation probes

Henrik Tydesjö May 5 2004
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QGP SIGNALS

• Jet Quenching
• J/Y Suppression
• - Strangeness enhancement
• Thermal photon production
• Light vector meson decays
• - Fluctuation probes

Henrik Tydesjö May 5 2004
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QGP SIGNALS

• Jet Quenching
• J/Y Suppression
• - Strangeness enhancement
• Thermal photon production
• Light vector meson decays
• - Fluctuation probes

Henrik Tydesjö May 5 2004
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Event-by-Event Net Charge Fluctuationsin Local
Regions of Phase Space
Decrease of Fluctuations proposed as a signal for
the QGP
Predictions range up to an 80 reduction
Henrik Tydesjö May 5 2004
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HADRON GAS
QGP
charge more evenly spread in plasma, due to the
fractional charges of quarks
Henrik Tydesjö May 5 2004
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Random Particle Emission
Charge q in each event
Normalized Variance
Variance of q
Henrik Tydesjö May 5 2004
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Hadron Gas
QGP (assuming thermal distributions)
Hadronized QGP (from theorist calculation)
BUT HEY!!! WAIT A MINUTE!!! Wouldnt this depend
very much on acceptance?
Henrik Tydesjö May 5 2004
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Charge is globally conserved
Henrik Tydesjö May 5 2004
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SIMULATION
Efficiency Dependence
Henrik Tydesjö May 5 2004
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Uncorrelated Background Contribution
Henrik Tydesjö May 5 2004
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Decays of Neutral Resonances (e.g. ? ,
?)introduce positive correlations between n and
n
?width 30º
Henrik Tydesjö May 5 2004
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Decays of Neutral Resonances
fres 0.3
Henrik Tydesjö May 5 2004
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Simple QGP model
producing 2 or 3 pions, separated in azimuth
(Gaussian width10º)
Henrik Tydesjö May 5 2004
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RHIC 1st run period
500 000 events
zvertex lt 17 cm
pT gt 200 MeV/c
Henrik Tydesjö May 5 2004
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Centrality of Collision
b
Impact parameter, b lt 10 fm

Henrik Tydesjö May 5 2004
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BBCs used for triggering corresponding to
92 of inelastic cross-section
Centrality classes determined from BBCZDC
information
5-10
0-5
Henrik Tydesjö May 5 2004
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pT , ? of positive and negative particles
Henrik Tydesjö May 5 2004
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Reduction not as large as predicted for
QGP Consistent with resonance gas
10 most central events
Henrik Tydesjö May 5 2004
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Fluctuations independent of centrality
10 most central events
Henrik Tydesjö May 5 2004
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SUMMARY
- An introduction was given to Quark
Gluon Plasma Relativistic Heavy-Ion
Collider (RHIC) PHENIX Experiment- The
behavior of Net-Charge Fluctuations in different
scenarios was described in simulations -
Results on Net-Charge Fluctuations in PHENIX was
presented Fluctuation result below pure
global charge conservation Reduction not
as drastic as predicted for a QGP
Consistent with resonance gas prediction
Henrik Tydesjö May 5 2004