Net Charge Fluctuations in Ultra-Relativistic Nucleus-Nucleus Collisions

Henrik Tydesjö May 5 2004

OUTLINE- The Quark Gluon Plasma

- The Relativistic Heavy Ion Collider (RHIC)The PHENIX Experiment

- QGP SignalsEvent-by-Event Net-Charge Fluctuations

SimulationsPHENIX Analysis

Phase Diagram of Nuclear MatterEarly Universe

HadronGas

QGP

Neutron StarsNeutron Stars??????

Ultra-RelativisticHeavy-Ion Collisions

???


QUARK GLUON PLASMA

DECONFINEMENT

PHASETRANSITION


QUARK GLUON PLASMA

CHIRAL SYMMETRYRESTORATION

Quark Masses 0


Relativistic Heavy Ion Collider (RHIC)Au+Au Collisions 100 AGeV per

beam


~ 460 Members

57 Institutions

12 Countries

Collaboration


Central Magnet

Beam-BeamCounters

Muon ArmSpectrometers Central Arm

Spectrometers


Central Arms

Pad Chambers

Charged ParticleTracking

Electron, Photon Detection

Hadron Identification


Pad Chambers- Multi-Wire Proportional Chambers

- Fine Granularity Pixel Pad Readout

- Provide Space Points for Track Recognition


Pad Chambers- Multi-Wire Proportional Chambers

- Fine Granularity Pixel Pad Readout

- Provide Space Points for Track Recognition

- 172,800 Readout Channels

- Chip-On-Board Technique Readout Cards (ROCS) Placed on the Chambers

- Data Transfer via Fiber Optic Links

Readout Card (ROC)


Event Display

CentralAu+Au

Collision

~ 400tracks in

central arms



QGP SIGNALS- Jet Quenching

- J/ Suppression

- Strangeness enhancement

- Thermal photon production

- Light vector meson decays

- Fluctuation probes

- Jet Quenching

- J/ Suppression




- Fluctuation probesHenrik Tydesjö May 5 2004

QGP SIGNALS


QGP SIGNALS- Jet Quenching

- J/ Suppression




- Fluctuation probes

NET CHARGE FLUCTUATIONS

Event-by-EventNet Charge Fluctuations

in Local Regions of Phase Space

Decrease of Fluctuationsproposed as a signal for the QGP

Predictions range up to an 80% reduction




charge more evenly spread in plasma,due to the fractional charges of quarks

HADRON GAS QGP


Charge q in each event:

nnq

Variance of q:22)( qqqV

Random Particle Emission:

chnnnqV )(

chnqVqv )()(

Normalized Variance:




Hadron Gas :1)( qv

QGP (assuming thermal distributions) :

28.0185

91

94

21)(

21)( 22

du qqqv

Hadronized QGP (from theorist calculation) :19.0)( qv

BUT HEY!!! WAIT A MINUTE!!!Wouldn’t this depend very much on acceptance?

NET CHARGE FLUCTUATIONSSIMULATION

Charge is globally conservedapQv 1)(



Efficiency Dependenceea ppQv 1)(



Uncorrelated Background Contribution)1(1)( bkga fpQv



Decays of Neutral Resonances (e.g. , )introduce positive correlations between n+ and n–

width = 30º



Decays of Neutral Resonances

fres = 0.3



Simple QGP model:yprobabilit equal with hadronize ,,, nscombinatioquark ddudduuu

producing 2 or 3 pions, separated in azimuth (Gaussian width=10º)



RHIC 1st run period

GeVsNN 130

~ 500 000 events

|zvertex| < 17 cm

pT > 200 MeV/c


b

Centrality of Collision

Impact parameter, b < 10 fm


~


BBCs used for triggering

corresponding to 92% of inelastic cross-section

Centrality classes

determined from BBC+ZDC information

0-5%5-10%



pT , of positive and negative particles


NET CHARGE FLUCTUATIONSReduction not as large as predicted for QGP

Consistent with resonance gas

Global ChargeConservation

10% most central events


NET CHARGE FLUCTUATIONSFluctuations independent of centrality

)(019.0)(007.0965.0)( syststatQv 10% most central events:


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


Net Charge Fluctuations in Ultra-Relativistic Nucleus-Nucleus Collisions

Documents

Transcript of Net Charge Fluctuations in Ultra-Relativistic Nucleus-Nucleus Collisions