Title: Correlations and Fluctuations in STAR
1Correlations and Fluctuationsin STAR
- Balance Function
- Excitation Function for pt Fluctuations
- Net Charge Fluctuations
- Discrete Wavelet Analysis
Quark Matter 2004Gary D. WestfallMichigan State
UniversityFor the STAR Collaboration
2The Balance Function
Bass, Danielewicz, and Pratt, PRL 85, 2689 (2000)
- Theoretical expectations for B(?y)
- PYTHIA representing pp collisions shows a
characteristic width of about 1 unit of ?y - Bjorken thermal model representing delayed
hadronization shows narrower balance function
width - Nucleon-nucleon ? wide
- Delayed hadronization ? narrow
- Experimental considerations
- Use ?? for all charged particles
- We will show centrality dependence for AuAu and
dAu - Use all centralities for pp
3Balance Function for AuAu at 200 GeV
4Balance Function Widths
Width is defined as weighted average of ?? for
0.1 ? ?? ? 2.0
Balance function for AuAu narrows in central
collisionsHIJING shows little centrality
dependenceSmooth dependence on Npart
5Balance Function for qinv
Fits are thermal K0 decay Thermal distribution
is
Narrowing of B(??) may be caused by transverse
flowUse B(qinv) to remove reference frame
dependenceAllow more direct comparison with
thermal models
6Width of Balance Function using qinv
Balance function B(qinv) for pions and kaons
narrows in central collisions even when using
Lorentz invariant observable
7Theoretical Predictions for the Balance Function
Cheng, Petriconi, Pratt, and Skoby,
nucl-th/0401008 Includes HBT, Coulomb,
resonances, strong interactions, radial flow,
conservation of S,Q,B Uses STAR acceptance
filter The agreement with the measured narrow
balance function in central collisions suggests
that charge conservation remains highly localized
at breakup
AuAu 200 GeV
8pt and Net Charge Fluctuations
- Search for dynamical fluctuations motivated by
predictions - Fluctuations in energy density due to localized
deconfinement - Increased fluctuations in energy density due to
long range correlations - Proximity to tri-critical and critical points
would lead to changes in fluctuation patterns - Production of DCCs
- Fluctuations from jet production
9Histograms of ltptgt
- AuAu at 20, 130, and 200 GeV
- 5 most central bin using min bias data, ? lt
1.0 - Real is wider than mixed
- ? Dynamical fluctuations
See poster by Claude Pruneau
10lt?pt,i ?pt,jgt as a Function of Incident Energy
- Compare AuAu at 20,130, and 200 GeV
- ? lt 1
- Compare with filtered HIJING
11lt?pt,i ?pt,jgt1/2/ltltptgtgt as a Function of Incident
Energy
- Compare AuAu at 20, 130, 200 GeV, ? lt 1
- Compare with CERES result from SPS, 17 GeV PbPb
lt?pt,i ?pt,jgt1/2/ltltptgtgt
12Different Scaling Methods for lt?pt,i ?pt,jgt
Scale with dN/d? - compare to ??pt
Centrality dependence may be sign of the onset of
equilibration in central AuAu collisions
13Comparison to Fpt
200 GeV AuAuSTAR Cuts ? lt 1.0?? 360?0.1 lt
pt lt 2 GeV
200 GeV AuAuSTAR withPHENIX Cuts ? lt 0.35??
2x90?0.2 lt pt lt 2 GeV
Acceptance matters
14Net Charge Fluctuations - Centrality Dependence
Increased dilution of correlation with increasing
Npart ?-,dyn larger at 20 GeV than 130 and 200
GeV Peripheral AuAu in agreement with inclusive
pp 1/N scaling violation
See poster by Claude Pruneau
15Net Charge Fluctuations - Dependence on ?
Acceptance
50-70 Central
0-10 Central
Ratio to ? lt 1
Ratio to ? lt 1
? acceptance
50-70 AuAu quite similar to pp 0-10 Monotonic
increase of correlation strength with beam
energy Flow is important (sensitivity to velocity
profile)
16Net Charge Fluctuations - Scaling
Multiplicity Scaling
dN/d? Scaling
Binary Scaling
Participant Scaling
17Discrete Wavelet Analysis
Suppression of correlation observed at high
pt Approaches thermalization
See poster by Mikhail Kopytine
18Conclusions
- Balance functions
- B(??), B(?y), and B(qinv) narrow in central AuAu
collisions - Consistent with trends of models incorporating
late hadronization - pt correlations
- Dynamic correlations observed at AuAu collisions
at 20, 130, and 200 GeV - Correlations/particle increase with incident
energy - Correlations/pair show little incident energy
dependence - May show onset of equilibration in central AuAu
collisions - Net Charge Fluctuations
- Larger ?-,dyn for AuAu at 20 GeV than 130 and
200 GeV - ?-,dynAuAu ? N ?-,dynpp
- Nbin scaling observed
- Discrete wavelet analysis
- Evidence for suppression of jet-like phenomena in
central AuAu collisions in the longitudinal
direction
19Extra Slides
20Balance Function for pp and dAu at 200 GeV
dAu
pp
21Delayed Hadronization
Early Hadronization ? Large ??
Suppose we could identify balancing charges
Late Hadronization ? Small ??
After Scott Pratt
22Definition of lt?pt,i ?pt,jgt
23Dynamical Net Charge Fluctuations
Definition
Independent Particle (Poisson) Limit
Measurement
Key Properties
Sensitive to two-particle correlations
Independent Particle Production
Independent NN Collisions
24Ratio of lt?pt,i ?pt,jgt using Pairs withqinv lt
0.1 GeV to All Pairs