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RRCP CP Measurement with Hadron DecaMeasurement with Hadron Deca
y Muons in Au+Au Collisions at y Muons in Au+Au Collisions at √s√sNN
NN=200 GeV=200 GeV
WooJin ParkWooJin Park
Korea UniversityKorea University
For the PHENIX CollaborationFor the PHENIX Collaboration
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ContentsContents
• Physics motivationPhysics motivation– from p+p to Au+Aufrom p+p to Au+Au
• PHENIX ExperimentPHENIX Experiment
• Muons from hadron decayMuons from hadron decay
• Analysis detail – decay muon analysisAnalysis detail – decay muon analysis– Normalized vertex distributionNormalized vertex distribution
– Decay slope measurementDecay slope measurement
• Summary / outlookSummary / outlook
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PHENIX single muon physicsPHENIX single muon physics
• Study particle production in (polarized) pp, pA and AA Study particle production in (polarized) pp, pA and AA collisions at forward (backward) rapiditycollisions at forward (backward) rapidity– Light hadrons: K, pi, p ( via muon decay channel ) Light hadrons: K, pi, p ( via muon decay channel )
– Heavy flavor: D, B… ( via semi-leptonic decay channel )Heavy flavor: D, B… ( via semi-leptonic decay channel )
• Probe nuclear medium effects: Probe nuclear medium effects: – Normal nuclear medium (dAu)Normal nuclear medium (dAu)
– Hot and dense nuclear medium (AuAu) Hot and dense nuclear medium (AuAu)
• SPIN measurement: gluon polarizationSPIN measurement: gluon polarization
How dense is the matter?
How strongly coupled is the matter?
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Physics motivation - Physics motivation - from p+p to Au+Aufrom p+p to Au+Au
• p+p collision p+p collision – Provide baseline reference for heavy-ion measurementsProvide baseline reference for heavy-ion measurements– Test of pQCD Test of pQCD
• p+A collision (d+Au at RHIC)p+A collision (d+Au at RHIC)– Probe Initial-State EffectsProbe Initial-State Effects / N / Normal nuclear mediumormal nuclear medium(Cold nuclear medium) effect(Cold nuclear medium) effect
– Shadowing / saturation @ low xShadowing / saturation @ low xAA
– ppTT broadening / energy loss broadening / energy loss
– Modifications of baryon productionModifications of baryon production• Au+Au collision Au+Au collision
– HHot and dense not and dense nuclear mediumuclear medium– QGP / phase transition to the new state of matterQGP / phase transition to the new state of matter
• Cu+Cu collision Cu+Cu collision – can give much better Ncan give much better Npartpart and N and Ncollcoll precision precision– RHIC provided Cu+Cu collisions at RHIC provided Cu+Cu collisions at √S√SNNNN==200, 62, 22 GeV200, 62, 22 GeV
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Light hadron’s Differential multiplicity in p+pLight hadron’s Differential multiplicity in p+p
hep-ex/0609032hep-ex/0609032
h+ h-
• PHENIX Run2 p+p data – hadron decay muonsPHENIX Run2 p+p data – hadron decay muons
• Provide baseline reference for d+Au / Au+Au measurementProvide baseline reference for d+Au / Au+Au measurement
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Physics Motivation – d+AuPhysics Motivation – d+Au
Three rapidity ranges probe different momentum fraction of Au partons
PHENIX North arm (y > 1.2) : small X ~ 0.003Shadowing/suppression regime
PHENIX Central arm (y ~ 0) : intermediate X ~ 0.020
PHENIX South arm (y < -1.2) : large X ~ 0.090Anti-shadowing/Cronin regime
From Eskola, Kolhinen, VogtNucl. Phys. A696 (2001) 729-746.
gluons in Pb / gluons in p
X
AntiShadowing
Shadowing
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RRCPCP in d+Au in d+Au Collisions - PHENIXCollisions - PHENIX
PHENIX - Phys. Rev. Lett. 94, 082302 (2005)
d direction Au direction
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RRdAudAu in d+Au Collisions in d+Au Collisions
Cronin-like enhancement at=0
Clear suppression as changes from 0 to 3.2
Measurements very consistent with initial-state effects
estimated by CGC.
D. Kharzeev hep-ph/0307037
Brahms PRL 93 (2004)
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Physics Motivation – Au+AuPhysics Motivation – Au+Au
• Two different effects can be expected (vs eta)Two different effects can be expected (vs eta)1.1. Low energy density(less energy loss) could make RLow energy density(less energy loss) could make RCPCP high high2.2. New regime of parton physics at low-x(CGC).New regime of parton physics at low-x(CGC).
• Gluon saturation at low-x has been predicted to suppress hadroniGluon saturation at low-x has been predicted to suppress hadronic yieldsc yields
• For Au+Au collisions, RFor Au+Au collisions, RCP CP « 1 can be expected« 1 can be expected
• PHENIX can measure RPHENIX can measure RCPCP with mesons with mesons
• Advantage: a lot of detector systematics cancel. Advantage: a lot of detector systematics cancel. • Disadvantage: most peripheral bin of 60-93% still corresponds to 14~15 Disadvantage: most peripheral bin of 60-93% still corresponds to 14~15 collisions and not all nuclear effects might be eliminated. collisions and not all nuclear effects might be eliminated.
RCP measurement
RRCPCP: Ratio between the central and peripheral yields scaled : Ratio between the central and peripheral yields scaled
by the number of binary collisions, where it is assumed that by the number of binary collisions, where it is assumed that peripheral is similar to ppperipheral is similar to pp
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LLight quark pight quark pTT suppression suppression
Photons not Photons not suppressed by the suppressed by the mediummedium
Mesons Mesons suppressed by suppressed by medium by factor medium by factor of of ~~55
Phys. Rev. Lett. 91, 072301 (2003)
Nuclear modification factor:
Suppression, Suppression, RRAAAA<<1, <<1, indicates strong indicates strong coupling of quarks to coupling of quarks to the produced medium.the produced medium.
0
Dir. 0
Dir.
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The PHENIX detectorThe PHENIX detectorOptimized for lepton Optimized for lepton
measurementsmeasurements
two forward muon spectrometerstwo forward muon spectrometers
Muons - forward arms Muons - forward arms ::
1.2 < |1.2 < || < 2.4 | < 2.4
p p 2 GeV/c 2 GeV/c
Electrons - central armsElectrons - central arms : : 0.35 0.35
p p 0.2 GeV/c 0.2 GeV/c
two central electron/photon/hadron spectrometerstwo central electron/photon/hadron spectrometers
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The PHENIX DetectorThe PHENIX Detector
South Muon arm : -2.2 < <-1.2 North Muon arm : 1.2 < <2.4
241 mb-1 Au+Au data at √sNN=200 GeV at 2004~2005 RHIC Run4
AuAu AuAu
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1 : Hadrons, interacting and absorbed (98%)2 : Charged/K's, "decaying" before absorber (≤1%)3 : Hadrons, penetrating and interacting ("stopped")4 : Hadrons, "punch-through"5 : Prompt muons, heavy flavour decay
TrackerIdentifier Absorber
Collision range
Collision1
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4
5
Muon HadronAbsorber
Symbols
Detector
Major Sources of Inclusive TracksMajor Sources of Inclusive Tracks
Item 2 is desired signal and rest of them are background in this analysis
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Identification of muons from hadronic decayIdentification of muons from hadronic decay
The yield of decay muons depends on The yield of decay muons depends on the collision location linearly.the collision location linearly.
Average flight Distance (blue
arrows)
Absorbers are in Red
TrackerIdentifier Absorber
Collision range
Positive z →
Decay muons (green tracks)
p
mL
decay eLpP
1),(
where, L is distance from the collision point to the absorber
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Z vertex DependenceZ vertex DependenceNormalized Muon event Z vertex
Linear shape of z vertex slope because c~100 [m].
/K decay dominates single muons.
Prompt or punch through background has no vertex dependent.
z [cm]
PHENIX PRELIMINARY
online trigger |z|<30cm
Fitting range
Decay muons
Prompt muons(haevy flavor decay)punch through hadrons
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Normalized Vertex DistributionNormalized Vertex Distribution
MB raw vertex distribution
Muon event vertex distribution
Normalized vertex distribution
z Normalized vertex distribution can be fit with a linear function :
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The normalized muon event vertex distribution :
)},()(),({),,(
)(
1 03
TeffT
T
TMBmeasured
PZZPdZddP
PZNd
ZN
Peripheralbinary
centralrecoT
peripheral
Centralbinary
peripheralrecoT
central
TdecayCP Np
NppR
/),(
/),(),(
Decay muons RCP :
Decay muon Rcp measurementDecay muon Rcp measurement
periperal
Tperipheralbinary
central
Tcentralbinary
CP
dpdNd
N
dpdNd
NR
2
2
1
1
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Decay slope measurementDecay slope measurement
0~20 %
20~40%
40~60%
60~93%
north south
1.2 < < 2.2, 1.5 < PT < 2.0
• decay slope should be measured on every centrality, PT and eta bins
• north and south arm show opposite slope
• decay slope corresponds to
• (efficiency corrected) decay slope ratio between central and peripheral bins is RCP
Event centrality was measured by BBC and ZDC correlation. Number of binary collisions was calculated by Glauber model
ddP
Nd
T
2
centrality
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North arm South arm
Differntial multiplicity (vs PDifferntial multiplicity (vs PTT))
Our approach works fine for both arm!!
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Decay slope measurement(vs eta)Decay slope measurement(vs eta)
yiel
d
No physics result yet
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RRCPCP vs Number of Binary Collisions vs Number of Binary Collisions
North arm South arm
Peripheral Central
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RRCPCP vs vs
Work in Progress
arb
itra
ry u
nit
Central Peripheral
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arb
itra
ry u
nit
arb
itra
ry u
nit
RRCP CP / R/ RAAAA vs p vs pTT
Statistical error bar only
Work in progress
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RRAuAuAuAu and R and RCPCP from Brahms from Brahms
(h+ + h-)/2 h-
Brahms PRL 91(2003)
• Low pT part scale with thLow pT part scale with the number of participants e number of participants (soft collisions)(soft collisions)
• strong suppression in centstrong suppression in central collisions (f. 4)ral collisions (f. 4)
• the suppression can not be the suppression can not be explained by hadronic eneexplained by hadronic energy lossrgy loss
• similar behavior at η 0 ansimilar behavior at η 0 and 2.2 d 2.2 Rapidity distribut Rapidity distribution will not change as a fuion will not change as a function of centrality.nction of centrality.
• RRCPCP similar to R similar to RAAAA (no me (no me
dium effect in semi-periphdium effect in semi-peripheral colls.)eral colls.)
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PHENIX Cu+Cu resultsPHENIX Cu+Cu results
• The suppression of RThe suppression of RCPCP is much smaller than what we can normally expect is much smaller than what we can normally expect
• Should note that pT range is different with Au+Au data• Cronin effect might affect a lot
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Summary / OutlookSummary / Outlook• RRCPCP measurement in Au+Au collision is important issue t measurement in Au+Au collision is important issue t
o understand nuclear effectso understand nuclear effects• Suppression at forward rapidity/enhancement at backwarSuppression at forward rapidity/enhancement at backwar
d rapidity in d+Au systemd rapidity in d+Au system• Strong suppression in central Au+Au collisionStrong suppression in central Au+Au collision• Suppression in Au+Au – strong coupling of quarks to thSuppression in Au+Au – strong coupling of quarks to th
e produced mediume produced medium• No big change of NMF with eta in Au+AuNo big change of NMF with eta in Au+Au• PHENIX Run4 Au+Au full data set will be served in twPHENIX Run4 Au+Au full data set will be served in tw
o months o months • New p+p results with much higher statistics(factor of 10New p+p results with much higher statistics(factor of 10
0) will be come out in a near future(RHIC run5)0) will be come out in a near future(RHIC run5)
Backup SlidesBackup Slides
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Going to higher Going to higher ηη in Gold-Gold in Gold-Gold
Higher rapidities - means smaller medium density => less supression - jet-quenching in longitudinally expanded source - Nch|η =2.0 < Nch| η =0 - initial and final-state effects have different dependenceon rapidity; final-state effects are maximal at mid-rapiditywhereas initial-state effects are enhanced in forward region
0-5%
5-10%
10-20%
20-30%
30-40%
40-50%
Polleri and Yuan (nucl-th/0108056)
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Efficiency CorrectionEfficiency Correction
• Efficiency can be calculated by embedding method (simulation + real data)
• Efficiency decrease as vertex goes to the detector - opening angle varies as a function of vertex - acceptance and multiplicity can change - combinatorial background
• Vertex bin by bin correction needed
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Efficiency – North armEfficiency – North arm
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Efficiency – South armEfficiency – South arm
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RRCPCP on d+Au collisions - BRAHMS on d+Au collisions - BRAHMS
Change of RCP from mid- to forward rapidities is stronger for central collisions than for semi-peripheral collisions
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High pt suppressionHigh pt suppression
- approximate binary scaling in semi-peripheral collisions
- strong suppression in central collisions (f. 4)
- similar behaviour at η 0 and 2.2 -> source extended to η ~2- longitudinal expansion at y >0
- Rcp similar to Raa (no medium effect in semi-peripheral colls.)
- the suppression can not be explained by hadronic energy loss
Brahms PRL 91(2003)
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Rcp for Au+Au h+, h- at Rcp for Au+Au h+, h- at ηη ~ 3.2 ~ 3.2
Centrality bins using
multiplicity in ||<2Glauber Model
<Ncoll> for 0-10% ~880
<Ncoll> for 40-60% ~ 78
<Ncoll> for 50-90% ~ 21
- persistent over 3 units in η
- no strong η dependency
- room for initial-state effects
- analysis of Raa in progress
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Suppression at Forward Rapidities at 200 GeVSuppression at Forward Rapidities at 200 GeV
= 0 = 3.2
RdA
u
dAu
RA
uAu
AuAu
Charged Hadrons
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NMF Dependence on CentralityNMF Dependence on Centrality
• The higher energy system begins to look more like pp The higher energy system begins to look more like pp collisions for less central events.collisions for less central events.
• The lower energy system shows Cronin enhancement The lower energy system shows Cronin enhancement similar to what is seen at SPS energies.similar to what is seen at SPS energies.
200 GEV
62.4 GEVRA
uAu
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PHENIX muon arms “x” coveragePHENIX muon arms “x” coverage
From Eskola, Kolhinen, VogtNucl. Phys. A696 (2001) 729-746.
gluons in Pb / gluons in p
X
PYTHIA open charm simulation
Particle production in the d direction (north) is sensitive to the small-x parton distribution in the Au nuclei; whereas in the gold (south) is sensitive to the large-x in Au