Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration...
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![Page 1: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/1.jpg)
Nov 2001 Craig Ogilvie 1
Angular Correlations at High pt:Craig Ogilvie for the Phenix Collaboration
Energy-loss:increased medium-induced
gluon-radiation
hadron distributionsoftened, broadened?
hard-scatteredparton during Au+Au
hard-scatteredparton from e.g. p+p
gluon radiation
cone of hadrons
p p
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Nov 2001 Craig Ogilvie 2
Correlations
2-particle angular correlation functions
Medium-induced gluon emission within QGP – predicted to be broad angles (>10 deg shown later in talk)– fragmentation angular-width may be broader – correlations at small may be broadened
study correlations from peripheral => central reactions– complementary to single-particle pt spectra and +hadron
back-to-back correlations.
)(N
)(N)C(
events mixed
real
21
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Nov 2001 Craig Ogilvie 3
Outline
Examples of angular correlation data from p+p, e+p Angle correlations from Au+Au at s1/2 = 130 AGeV
– pt dependence – centrality dependence
Simulations of possible sources of angular correlations – work in progress
Measurements for this year-2 Which observable makes a link between experiment and theory
![Page 4: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/4.jpg)
Nov 2001 Craig Ogilvie 4
ISR Data p+p s1/2 = 62 GeV
CCOR Collaboration (M. J. Tannenbaum) Trigger particle (neutral) with pt > 7.0 GeV/c
– azimuthal distribution of charged particles– strong back-to-back and near-side emission
back-to-backnear-side
![Page 5: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/5.jpg)
Nov 2001 Craig Ogilvie 5
Transverse Momentum Within Jet
jT transverse momentum with respect to “jet” axis
Trigger PTjTJetJet
PT jT
PoutkT
<| jT|> = 400 MeV/c, use as one check for what we observe in HI
CCOR CollaborationPhys. Lett. 97B, 163 (1980))
![Page 6: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/6.jpg)
Nov 2001 Craig Ogilvie 6
HERA e+p Angular Distribution Within a Jet
Within a jet Yield of two particles
separated by angle 12
Transformed to
)/)sin(ln()/ln( 12
coneAngleP
coneAngle
Yield peaked atsmall 12 ,
More complicated variablechosen to match expt. with what can be calculated.
![Page 7: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/7.jpg)
Nov 2001 Craig Ogilvie 7
Au+Au s1/2 = 130 AGeV
1.5M events, summer 2000 Phenix data -20 < collision vertex < 20 cm Central arm tracks
– momenta from drift chamber tracks– 1 < pt < 2.5 GeV/c
Centrality cuts expressed as a % of int=7.2b
– (zero degree energy) vs (charge in beam counters) Correlation functions
– mixed events from similar beam-vertex, centrality– 2-track acceptance cuts on both real, mixed pairs
![Page 8: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/8.jpg)
Nov 2001 Craig Ogilvie 8
Correlations Presented Today
Both hadrons between 1< pt < 2.5 GeV/c Two correlations formed
– both hadrons in west arm of PHENIX– one hadron in east, west arm of PHENIX
Studied as a function of pt, centrality
)(N
)(N)C(
events mixed
real
21
![Page 9: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/9.jpg)
Nov 2001 Craig Ogilvie 9
Possible Causes of Angular Correlation
Elliptic flow, jet fragmentation produce azimuthal correlations Analysis challenge to extract both
– jet fragmentation extends to narrow angles» near-side ~ 0-30 deg
– flow extends over full range with a harmonic oscillation
![Page 10: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/10.jpg)
Nov 2001 Craig Ogilvie 10
40-92% Centrality, 1.0 < pt < 2.5 GeV/c
Near-angle correlation fallsmore steeply than back-to-back correlation
Add correlations by ensuringsymmetry near 90o
Both hadrons in west arm
One hadron in west arm,other in east arm
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Nov 2001 Craig Ogilvie 11
1<pt<2.5 GeV/c (40-92%)
offset)2cos(a
2)/(2
1
widtheC
offset)2cos(a Csymmetric (elliptic flow) fit (poor)
stronger near-anglecorrelation than back-to-back
phenix preliminary
phenix preliminary
![Page 12: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/12.jpg)
Nov 2001 Craig Ogilvie 12
Centrality Dependence
40 to 92%
0 to 5%
1) near-angle correlation in central reactions: broader, smaller amplitude
2) elliptic flow v.small in central reactions
phenix preliminary
phenix preliminary
1< pt < 2.5 GeV/c
![Page 13: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/13.jpg)
Nov 2001 Craig Ogilvie 13
Au+Au Centrality Dependence
offset)2cos(a2)/(
2
1
width
eC
npart
width of correlation broadensfor more central reactions
systematic errors: how fit changes for different normalization criteria
1< pt < 2.5 GeV/cphenix preliminary
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Nov 2001 Craig Ogilvie 14
First-Order Comparison to p+p
npart
GeV/c 34.0
GeV/c 4.1)2
20sin(||
)2
sin(||
0
T
Thadron
T
j
pangleWidth
j
for peripheral data, on average both hadrons comparable pt
pp running this year impt.
phenix preliminary
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Nov 2001 Craig Ogilvie 15
Pt Dependence of Correlation
Fit to full function, display only offset)2cos(osc
near-anglecorrelation strongestfor high-pt
1.0 < pt < 2.5 GeV/c
0.5 < pt < 1.0 GeV/c
0.2 < pt < 0.5 GeV/c
central 40 –92%
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Nov 2001 Craig Ogilvie 16
Feasible Causes of Near-Angle Correlation(next slides)
Resonance decay leading to correlated particles
Decay of K0s (in progress, not shown today)
Fragmentation of high-pt parton Other….?
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Nov 2001 Craig Ogilvie 17
1) UrQMD Au+Au2) tag all resonances3) decay, apply pt cut
correlation strength 0.001due to decay of resonances5-10 times smaller than data
Resonance Study
1.0 < pt < 2.5 GeV/c|| <0.35
![Page 18: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/18.jpg)
Nov 2001 Craig Ogilvie 18
PYTHIA 6p+p at s1/2 = 130 GeV
Hard-Processes
1.0 < pt < 2.5 GeV/c, || <0.35
C
C
near-angle correlation strongerthan back-to-back
small acceptance reducesback-to-back acceptance fordifferent x1, x2
width of 0.35 rad = 20 degcomparable to periph. Au+Au<pt> scattered parton ~ 3GeV/c
![Page 19: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/19.jpg)
Nov 2001 Craig Ogilvie 19
Possible Reach With Year-2 Data
p+p baseline data 30-100 times more Au+Au statistics Higher-pt reach, pt > 5 GeV/c Asymmetric pt cuts, pt1 > 5 GeV/c, pt2 > 2 GeV/c
– better match to transverse momentum within jet Tag PID of leading hadron, correlate with all others
– 0 correlated with others» heading towards correlated with others
– leading p or p» speculative possible sensitivity to gluon vs quark jets
![Page 20: Nov 2001 Craig Ogilvie 1 Angular Correlations at High pt: Craig Ogilvie for the Phenix Collaboration Energy-loss: increased medium-induced gluon-radiation.](https://reader035.fdocuments.us/reader035/viewer/2022062518/56649e545503460f94b4b51a/html5/thumbnails/20.jpg)
Nov 2001 Craig Ogilvie 20
Making Connection With E-Loss Theory
Recent calculations, e.g. Baier, Schiff, Zakharov, calculate how much energy is radiated to outside a given cone angle
250 GeV jet1/3 of E is radiated > 20o
Can this formalism calc C()?Do we need new observablethat expt and theory can both use
Ann. Rev. Nucl. Sci 2000, 50, p37
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Nov 2001 Craig Ogilvie 21
Summary
High-pt near-angle correlations slightly stronger than back-angle correlations – well reproduced by Gaussian superimposed on oscillation– width of correlation broadens for more central reactions
Possible causes of near-angle correlation– decay of resonances
» factor of 5-10 smaller than observed signal
– weak decay of K0s , in progress
– fragmenting hard-physics» needs higher pt reach to be convincing» in this scenario, increasing width, broader fragmentation» open question: medium-induced gluon emission?