‫ژ‬運動量粒子生成とJet QuenchingPhysics Target (I) -Jet

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

quenchingJet will loose its energy via gluon radiation in hot dense
medium, and the energy distribution of Jet will be modified
hard-scatteredparton during Au+Au

cone of hadrons “jet”

increased gluon-radiation
within plasma?

p

p0 without energy loss
Yield [GeV-1c]

hard-scatteredparton from e.g. p+p

High pT hadrons
arefragments of Jets!

pHot dense medium?

p0 with energy loss

Energy Loss!
pT [GeV/c]
X.-N., Wang, PRC 58 (1998)2321

Expectations in nuclearcollisions• In the absence of nuclear effects, expect
point-like scaling:ó AAµ the ratio of number of point - like sources = A 2
ó pp
N AA (b )= Ncoll ; number of binary collisions for a certain bN pp– Ncoll fl calculated using Glauber model• Previously observed effects:– Nuclear Shadowing– kT broadening (“Cronin effect”)

What to compare• We measure yield per collision for certain
centrality bins
d2 óYield(p T , b ) =Nevent (b ) 2∂ p T dp T dy1• Ratios of interest:
Yield central / · N coll Ò central
Yield pp

Yield central / · N coll Ò central
Yield peripheral / · N coll Ò peripheralp + p( p ) Data as Reference• Data available oflarge range of ÷s,
but not for 130 GeV• Power law fit to:A(p0 + pT )-n• Interpolate pT to÷s=130 GeV‡ reference p+pspectrum at our ÷sCERN SPS での測定
• データ p0 のスペクトル– 200 AGeV S+S (WA80)– 158 AGeV Pb+Pb (WA98)• pQCD ‫ב‬算との比ѕ– kT broadening を考慮すると良い一致が得られる– パートンのエネルギーロスは無い？

Cronin 効果• pA 衝突での生成断面積のターゲット依存性
spA(pT) = spp(pT) Aa(pT)– High pT 領域で、a (pT) > 1• 重イオン衝突でも同様な現象• パートンの多重衝突‡ kT broadening

The device: PHENIX EMCal

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

6 lead- scintillator (PbSc) sectors (15500 towers)

&
Pb Sc

Pb Sc

Pb Sc

Pb Sc

2 lead- glass (PbGl) sectors (9200towers)
Acceptance: |h|<0.37 at midrapidity, f=pPbGl

Pb Sc

PbSc

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

Analysis (Neutral Pion)• Using Electro-magnetic Calorimeter– 1GeV/c<pT<5(10)GeV/c for p0 in Year-1(2)!

• Calculate gg invariant mass spectra andsubtract combinatorial background• Excellent Energy
scale accuracy andresolution• Efficiency andacceptance corrections

Background subtracted(Red-Blue)

Invariant Mass[GeV/c2]•Embedding single p0
into real event• Systematic Error:•pT independent- 9%•Overall- 20-30%
pT [GeV/c]

Invariant Mass[GeV/c2]

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

Neutral Pion pT spectra• Suppression is quantified relative to p+p “baseline” scaled byNumber of binary collisions (Ncoll)• ÷sNN=130 GeV and 200GeV Au+Au data are shown• Central collisions data are inconsistent with p+p “baseline”
scaled by Ncoll, while peripheral data are consistentInvariant Yield [(GeV/c)2]

PHENIX Coll., PRL88, 022301 (2002)

÷sNN=200GeV

÷sNN=130GeV
70-80% PERIPHERAL
Ncoll =12.3 ±4.0

IX
NEHP

pT [GeV/c]pT [GeV/c]ryainmelirP

0-10% CENTRAL
Ncoll =975±94

Yield Suppressed!

pT [GeV/c]

Nuclear Modification factor

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

1/N events d 2 N AA /dp Tdh
Yield central / · N binary Ò centralR AA (p T ) ==· N binary Ò(d 2s pp /dp Tdh/s pp inelastic )Yield pp

Ratio of “Yieldper collision”

Nuclear Effects can be explored: multiple scattering energy loss, etc.
If there is NO nuclear effect, ratio = 1 (basic hard process)Beam Energy DependenceCentrality Dependence

0-10%÷sNN=200GeVPHENIX Preliminary

Pb+Pb ÷sNN=17.3GeV
Multiple scattering(Cronin)
RAA(2 GeV/c) ~0.45RAA(8 GeV/c) ~ 0.1670-80%

binary scaling÷sNN=130GeV

0-10%÷sNN=200GeVSuppression at higher pT and higher centrality (Energy loss?)

High pT Neutral Pion Suppression –Comparison To Theory•

pQCD calculations:– P. Levai,
Nucl.Phys.A698 (2002) 631– X.N. Wang,
Phys.Rev.C61 (200)064910– I. Vitev,
talk at QM2002•

so far suppression notdescribed by theories– calculations without energy
loss completely off– energy loss calculations
show different pTdependence

The Drift ChamberCoverage:
Dj = 90° Dh = 0.7

6 module types:
X1,U1,V1,X2,U2,V2

Wide range measurement of p’s

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

Au + Aus NN = 200 GeV

Using RICH!

• Most of central arms used tomeasure the pion spectrum• Powerful cross-checks ofresults

Charged Hadron spectra• Strong shape change with centrality• Same tendency as p0 is seen

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

÷sNN=200GeV

Ratios tominimum bias
spectrum
Most Peripheral:pT<2 GeV/c :absence of flowpT>2 GeV/c :absence ofsuppressionCentral to Peripheral
Ratio(A variation on RAA)

• Should be 1 if
there is NO
nuclear effect• Suppression seenin threeindependentmeasurements

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

Yield central / · N binary Ò central

Yield peripheral / · N binary Ò peripheral

Centrality
Dependence ofSuppression• Nuclear
Modification Factor
as a function of Npartp0• Binary-scaled yield
as a function ofNparth±

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

PHENIX Preliminary

4 < pT < 6 GeV/c

Jets in p+p
trigger g > 2.5GeVDfp0

raw differential yields

PHENIX Preliminary

pp@200GeV

2-4 GeV

Mickey Chiu @ QM02

incoming partonsassociated h±with pT requirement• Jet structure wasobserved in azimuthal
correlation in pp at
sqrt(Spp)=200GeV.

•black = pair distribution•green = mixed event pair distribution•purple = bkg subtracted distribution

Evidence for jets in Au+Au
C2 (Au + Au) = C2 ( p + p) + A * (1+ 2v 22 cos(2Df ))†Ansatz: high pT triggered Au+Au event is superpositionof high pT triggered p+p event and elliptic flow:
v2 from reaction plane analysis
A fit in non-jet region (0.75<|Df|<2.24)
Peripheral

CentralD. Hardtke, STAR plenary talk QM02

Back-to-back jet structure seen

Near side jets still exist
Away side jets disappear

1/Ntrig dN/dDf

PHENIX Preliminary

2- 4 GeV

1 / Nt r i g d N / dDh

Evidence for jets in Au+Au

Mickey Chiu @ QM02

Df

PHENIX Preliminary

2-4 GeVDhapythia*<e>• Use p-p analysis as a reference for Au-Au jet signal• Correlation seen simultaneously in Dj and Dh (Jet Cone)PHENIX Preliminary• In pT 2-4 GeV/c, Jet-Like Signal
dominates over elliptic flowcomponent.
• This Jet-Like Signal approx. flatwith centrality (no systematicerrors yet)

Ratio =2d(Df)[C(Au+Au)
A*(1+2v
22 cos( 2Df ))]ÚÚ d (Df )[C ( p + p)]
2Indication of no change offragmentation in near side?

D. Hardtke, STAR plenary talk QM02

More evidence for jets
- Charged-Charged Correlation -PHENIX PreliminaryC(Df)•Correlation fcn for charged hadrons.
•Observe large asymmetry•Fit to gaussian + cos2f.
•Width of gaussian peak vs. pt.
•For a jet, the transverse momenta <jT> ~ 400
MeV, independent of pt (dashed curve below).
Correlation width µ jT/pTpTjT

Df

PHENIX Preliminary

Another hint of no change offragmentation in near side?

PHENIX Preliminary

PHENIX Preliminary

01

2Paul Constantin @QM02 Df3

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

Physics Target (II) -Interplay of soft and hard processes• Baryon number will be transported via gluon junction to midrapidity region (Soft process)– Effective string tension for baryons produced gets larger than mesons– Another pT kick is given to baryons• Baryon/meson ratio will do!

Anti-proton/p ratio– Jet quenching (hard) enhances baryon number transport (soft) at
moderate hight pT region– p+, p- and p0 suppress, pbar and p enhance
Strong centrality
0-10%
dependence!

70-80%

I. Vitev and M. Gyulassy, PRC65(2002)041902

Puzzle: Baryons at high pt• A puzzle in high pt data:p/pbar yield is comparable orhigher than pion in 3-4 GeV/cfor central collision.
• If pbars are from jet
fragments, pbar/p ratio
should be small at high pt.
– Peripheral collision agree withthis expectation.

• How those high pt baryons
are produce?
– Very strong radial flow?
– Gluon junction model?
hep-ex/0209030

JPS Autumn meeting at Rikkyo Univ., Sep. 10, 2002

p/pi 200GeV

pbar/pi 200GeV

pbar/p and p/p
Ratios strongly
depend on centrality,
and less depend on
beam energies
Interplay of soft andhard is well seen!

pbar/pip/pi!
noisrapm
Co(h+ + h-)/2 と p0
• (h+ + h-)/2 と p0 は同じではない– パイオンの収量が支配的であれば正しい– High pT 領域では反෩子
収量が p0 収量と同程度

More puzzle in pT >4 GeV/c
Proton identification not available.
Use pi0 and non-identified hadrons
Are the protons_ of the hadron yield
up to 9 GeV/c ?

3D Hydro

Brief Summary of
Our Hydro Results• Full 3D hydro!
! No Bjorken scaling ansatz! No cylindrical symmetry! (t, hs, x, y) coordinate

130AGeVT.Hirano, Phys.Rev.C65(2002)011901.

• T ch ≠ T th !
ÿSuppression of radial, elliptic
flow and HBT radii in comparison
with the conventional hydro results.
130AGeV

T.Hirano and K.Tsuda, nucl-th/0205043(Phys.Rev.C, in press).

Brief Summary ofOur Hydro Results (contd.)suppression•Suppression of radial flow
as a result of chemical
non-equilibrium properties

PHENIX
130A GeV dataTch• pT slopes become
insensitive to Tth.
‡Need hard components

The Hydro+Jet Model
3D HydroPYTHIAPYTHIA
3

PDF:
Collinear: CTEQ5LO
kT: Gaussian<kT2>=1GeV2/c2

E3d psUA1p+pbar
200 GeV

Fragmentation:
IndependentFragmentation
Modelx1fax2fb

ds jetppnhadro

4Parton energy loss:dE/dx(I will discuss later…)= K Â Ú g (kT ,a )kT ,a dkT ,a g (kT ,b )kT ,b dkT ,babds abÆcd
¥ Ú f a ( x1 , Q )dx1 f b ( x2 , Q )dx2 E
d3p2

hadro

2

nsPHENIXp+p 200GeVpQCD LO:

q + q ' Æ q + q ' , q + q Æ q '+ q 'q + q Æ g + g, q + g Æ q + g
g + g Æ q + q, g + g Æ g + g*Initial and final state radiation are included.

Time Evolution in theHydro+Jet Model
Full 3D
hydroHydro evolution
0Jets

t0 =0.6fm/c
Freestreaming•Formation time~0 fm
For jets with pT>2GeV/c,
1/pT<0.1fm/c<<1fm/c•Momentum dist. fromPYTHIA ver. 6.2

Particle spectra
through CooperFrye formulatf ~10fm/ctEnergy loss

Fragmentation•Thermalization time
= Initial time of fluids•After hydro simulation,
all survival jets fragment
into hadrons.

•Initial parameters inhydro have been alreadytuned.

•We neglect interactionof fragmented hadrons.

Phenomenological
Parton Energy Loss
• Incoherent Model:

dE e= = esr (t , x (t ) )dx l
From hydro simulation
eeeeJetlpartonic medium

e: energy deposit per scattering
l: mean free paths: parton-parton cross section
r: thermalized parton density*Neglecting energy loss
in the hadron phase.
r mixed = f QGP (t , r )r (TC )E (t , r )- Ehad
f QGP =EQGP - Ehadp0 Spectra in sNN1/2=130 GeV
Central Collisions•<dE/dx>~0.85 GeV/fm@t0=0.6 fm/c
•Onset of hard component
pT~1.5 GeV/cdE= 0.06 r (t , r ) (GeV/fm)dx
the best fit valueª 0.2 (GeV/fm)

HIJING:dE/dx = 0.25 (GeV/fm)
X.-N. Wang, NPA698(2002)296c

Models for Parton Energy Loss
•Incoherent modeldE= 0.06 r (t , x (t ))dx•Coherent (LPM) model
A model motivated bya) GLV 1st order, or b) BDMPS for E>Ecr2
eff , a: free (adjustable) parameter“Transport” coefficient qtfL~RAuÊ2E ˆ2˜˜qˆLeff = dt r (t , x (t ))(t - t 0 )logÁÁ1 +2
m=0.5 GeV/ct0Lm

DE = aqˆLÚË¯

M.Gyulassy et al., Nucl.Phys.B571(2000)197; R.Baier et al., Nucl.Phys.B483(1997)291.

Suppression Factor (PHENIX)

0-10% Central(Ncoll=975±94)

RAA(2 GeV/c) ~0.45
RAA(8 GeV/c) ~ 0.16

RAA ( pT )d 2 N A + A dpT dh=N binary d 2 N N + N dpT dh

From D. d’Enterria, talk at QM2002.

Suppression Factor in sNN1/2=200 GeV
Central Collisions•Suppression factor RAA
Incoherent model: increaseCoherent model: almost flat

•Experimental data (PHENIX):‡ gradually decrease

RAA ( pT )d 2 N A + A dpT dh=
N binary d 2 N N + N dpT dh

RAA(pT) depends on themodels of parton energy loss.

Back-to-Back Correlations ofHigh pT HadronsdN
C2 (Df ) =dDhÚ
N triggerdDf dDhpT (GeV/c)

1

6

STAR
Triggeredparticles

42

Associatedparticles
-0.7

0h

0.7

p+pA+A

Back-to-Back Correlation (STAR)

4<pt(trig)<6 GeV/c data

Peripheral 60-80%

Central 0-5%
From D.Hardtke, talk at QM2002.

RAA and C2 in sNN1/2=200 GeV CentralCollisions•Near-side jets:
Almost independent•Away-side jets:
Depend on magnitude ofenergy loss

We fail simultaneous
reproduction of RAA and C2.
‡Need another mechanism今後のЁ題• 3K：‫ژ‬統‫ژ、ב‬精度、‫ژ‬運動量• 粒子の種์– パートンの種์：クォークの‫ޑ‬量の違い• ૣ磁シャワーでは、ૣ子とミューオンの‫ޑ‬量の違いにより大きな差。QCD gluon
bremstrahlung でも同様か？
• パイオンとK中間子（？）– パートンの種์：グルーオンとクォークの違い• Stopping power が違うか？
• 粒子・反粒子の運動量分布の Ncoll 依存性