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

22

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

33

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?

44

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

55

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

66

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

77

RRCPCP in d+Au in d+Au Collisions - PHENIXCollisions - PHENIX

PHENIX - Phys. Rev. Lett. 94, 082302 (2005)

d direction Au direction

88

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)

99

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

1010

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.

1111

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

1212

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

1313

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

23

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

1414

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

1515

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

1616

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 :

1717

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

1818

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

1919

North arm South arm

Differntial multiplicity (vs PDifferntial multiplicity (vs PTT))

Our approach works fine for both arm!!

2020

Decay slope measurement(vs eta)Decay slope measurement(vs eta)

yiel

d

No physics result yet

2121

RRCPCP vs Number of Binary Collisions vs Number of Binary Collisions

North arm South arm

Peripheral Central

2222

RRCPCP vs vs

Work in Progress

arb

itra

ry u

nit

Central Peripheral

2323

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

2424

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.)

2525

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

2626

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

2828

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)

2929

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

3030

Efficiency – North armEfficiency – North arm

3131

Efficiency – South armEfficiency – South arm

3232

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

3333

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)

3434

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

3535

Suppression at Forward Rapidities at 200 GeVSuppression at Forward Rapidities at 200 GeV

= 0 = 3.2

RdA

u

dAu

RA

uAu

AuAu

Charged Hadrons

3636

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

3737

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