Energy dependence of minijet structure in Au-Au collisions at √ s NN = 19 – 200 GeV
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Energy dependence of minijet structure Energy dependence of minijet structure in in Au-Au collisions at Au-Au collisions at √ √ s s NN NN = 19 – 200 GeV = 19 – 200 GeV STAR Collaboration DNP 04 Michael Daugherity Graduate Student - University of Texas
description
Energy dependence of minijet structure in Au-Au collisions at √ s NN = 19 – 200 GeV. STAR Collaboration DNP 04. Michael Daugherity Graduate Student - University of Texas. Correlation Measures I. ρ sibling ( p 1 ,p 2 ). Event 1. ρ reference ( p 1 ,p 2 ). Event 2. Normalize with. - PowerPoint PPT Presentation
Transcript of Energy dependence of minijet structure in Au-Au collisions at √ s NN = 19 – 200 GeV
Energy dependence of minijet structure inEnergy dependence of minijet structure in
Au-Au collisions at Au-Au collisions at √√ssNNNN = 19 – 200 GeV = 19 – 200 GeV Energy dependence of minijet structure inEnergy dependence of minijet structure in
Au-Au collisions at Au-Au collisions at √√ssNNNN = 19 – 200 GeV = 19 – 200 GeV
STAR Collaboration
DNP 04
STAR Collaboration
DNP 04
Michael Daugherity
Graduate Student - University of Texas
Daugherity – DNP 04
University of Texas 2
ρ(p1,p2) = 2 particle density in momentum space
Event 1
Event 2
ρsibling(p1,p2)
ρreference(p1,p2)
Correlation Measures ICorrelation Measures INumber Correlations
)()(),(
),(),(),(
2)1(1)1(21)2(
212121
pppp
pppppp refsib
Or, defining Δρ as a histogram, bin (a,b) can be written as:
ba
baba
)n(n)n(n
nnnnn
)(
We calculate this as a function of (ηΔ = η1 –η2, ΦΔ = Φ1 – Φ2), separation in pseudorapidity and azimuth (axial momentum space)
Normalize with baref nnn )((n)ρ
Δρ(n)
ref
is a per-particle measure
refρ
ΔρNrN )1ˆ( the previous talk used
Daugherity – DNP 04
University of Texas 3
STAR Au-Au 62 GeV Number Correlations
centrality
STAR Preliminary
ηΔΦΔ ηΔ
ΦΔηΔ
ΦΔηΔΦΔ
Peripheral
proton-proton 200 GeV
• Correlation structure evolves smoothly from p-p to central Au-Au
• Measure of minimum-bias jets (minijets)
ηΔΦΔ
ηΔΦΔ ηΔ
ΦΔηΔ
ΦΔηΔΦΔ ηΔ
ΦΔ
)(
)(
n
n
ref
Central
Daugherity – DNP 04
University of Texas 4
pt Correlation
STA
R Pre
limin
ary
Correlation Measures IICorrelation Measures IIAbove plots showed number correlations, we can also find correlations in pt
η Δ
ΦΔ
Number Correlation
( : )
( )t
ref
p n
n
STAR 130 GeVmid-central
bttattt pnppnpn)ρ(p )ˆ()ˆ(: Δba nnnnρ(n) )()( Δ
We will discuss pt correlations where bin (a,b) is the pt
covariance between particles with separation (ηΔ,ΦΔ)
refρ
ρNΔ
Daugherity – DNP 04
University of Texas 5
STAR 62 GeV pt Correlations
70-80% 55-65% 45-55%
5-10% 0-5%35-25%
STAR Preliminary
Centrality Dependence of Centrality Dependence of pptt Correlations Correlations
centrality
)(
):(
n
np
ref
t
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University of Texas 6
Peripheral
19 GeV 62 GeV 130 GeV 200 GeV
Mid-centralSTAR Preliminary
Energy Dependence of Energy Dependence of pptt CorrelationsCorrelations
19 GeV 62 GeV 130 GeV 200 GeV
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University of Texas 7
70-80% 45-55% 15-25%
same as above, but with cos(ΦΔ) and cos(2ΦΔ) components subtracted
STAR Preliminary
Isolate “same-side” peak (ηΔ,ΦΔ≈ 0) by subtracting azimuth multipole components
62 GeV unsubtracted data
Isolating Minijet StructureIsolating Minijet Structure
62 GeV subtracted data
Energy and Centrality Dependence of Minijets Energy and Centrality Dependence of Minijets
Mid-central
Central
Peripheral19 GeV 62 GeV 130 GeV 200 GeV
STAR Preliminary
subtracted data
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University of Texas 9
• Minijets (minimum-bias parton fragments) produce number and pt correlations in axial momentum space
• Minijet structure is revealed with minimum bias by two-particle correlations formed with no trigger particle
• pt correlations attributed to minijets are strongly energy and centrality dependent
• Minijet correlation structure probes the colored medium produced in RHIC Au-Au collisions
SummarySummary
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University of Texas 10
Extra Slides
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University of Texas 11
Extra Slide 1 – Direct Method for pExtra Slide 1 – Direct Method for ptt Correlations Correlations
ηΔ
ΦΔ
ΦΔ
ηΔ
Sum over events
Single Event
a
b
# of pairs
Find pt covariance between particles in bins a and b: bttattt pnppnpn)ρ(p )ˆ()ˆ(: Δ
Normalize to number of particles in bins a and b: baref nnn )(
Construct pt correlation for all bins (a,b): ( : )
( )t
ref
p n
n
Daugherity – DNP 04
University of Texas 12
The pt correlation data were obtained with the fluctuation inversion method
Calculate Δσ2pt:n then numerically invert to find pt correlations
see hep-ph/0410180 and hep-ph/0410182 for details
Fluctuation Inversion in a Nutshell:
ji ref
jinptjin
jinptK
,,
2:
),,(
),,:(4
variance difference
event-wise mean pt variance minus variance of inclusive reference distribution
(see nucl-ex/0308033)
“discrete integral”
2D binning function
pt correlation
Extra Slide 2 – Fluctuation InversionExtra Slide 2 – Fluctuation Inversion
