Correlations and Fluctuations in STAR - PowerPoint PPT Presentation

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Correlations and Fluctuations in STAR

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Theoretical expectations for B ... Real is wider than mixed. Dynamical fluctuations. Histograms of pt See poster by Claude Pruneau ... – PowerPoint PPT presentation

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Title: Correlations and Fluctuations in STAR


1
Correlations 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
2
The 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

3
Balance Function for AuAu at 200 GeV
4
Balance 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
5
Balance 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
6
Width of Balance Function using qinv
Balance function B(qinv) for pions and kaons
narrows in central collisions even when using
Lorentz invariant observable
7
Theoretical 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
8
pt 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

9
Histograms 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
10
lt?pt,i ?pt,jgt as a Function of Incident Energy
  • Compare AuAu at 20,130, and 200 GeV
  • ? lt 1
  • Compare with filtered HIJING

11
lt?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
12
Different Scaling Methods for lt?pt,i ?pt,jgt
  • Scale with Npart

Scale with dN/d? - compare to ??pt
Centrality dependence may be sign of the onset of
equilibration in central AuAu collisions
13
Comparison 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
14
Net 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
15
Net 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)
16
Net Charge Fluctuations - Scaling
Multiplicity Scaling
dN/d? Scaling
Binary Scaling
Participant Scaling
17
Discrete Wavelet Analysis
Suppression of correlation observed at high
pt Approaches thermalization
See poster by Mikhail Kopytine
18
Conclusions
  • 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

19
Extra Slides
20
Balance Function for pp and dAu at 200 GeV
dAu
pp
21
Delayed Hadronization
Early Hadronization ? Large ??
Suppose we could identify balancing charges
Late Hadronization ? Small ??
After Scott Pratt
22
Definition of lt?pt,i ?pt,jgt
23
Dynamical Net Charge Fluctuations
Definition
Independent Particle (Poisson) Limit
Measurement
Key Properties
Sensitive to two-particle correlations
Independent Particle Production
Independent NN Collisions
24
Ratio of lt?pt,i ?pt,jgt using Pairs withqinv lt
0.1 GeV to All Pairs
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