phenix hcp2007m. j. tannenbaum 1/35 measurements of hard-scattering by phenix at rhic m. j....

PHENIX HCP2007 M. J. Tannenbaum 1/35

Measurements of Hard-Scattering Measurements of Hard-Scattering by PHENIX at RHICby PHENIX at RHIC

M. J. TannenbaumBrookhaven National Laboratory

Upton, NY 11973 USA

Hadron Collider Physics Symposium La Biodola, Isola d’Elba, Italy

May 20-26, 2007

For the PHENIX Collaboration


The CERN ISR was the first Hadron The CERN ISR was the first Hadron Collider and made many discoveries and Collider and made many discoveries and

developed many techniques which are in use developed many techniques which are in use in Au+Au and p-p collisions at RHIC today. in Au+Au and p-p collisions at RHIC today.

• Proof using same-side and away side two particle correlations that high pT particles in p-p collisions are produced from states with two roughly back-to-back jets which are the result of scattering of constituents of the nucleons as described by QCD, which was developed during the course of these measurements.

G. Giacomelli and M. Jacob, Phys. Rept. 55 (1979) 1-132 M. Jacob and K. Johnsen, CERN Yellow Report 84-13

• The rapidity plateau (although several of my RHI colleagues don’t believe in a plateau). Will not be discussed in this talk. • Hard scattering in p-p collisions via particle production at large pT which proved that the partons of DIS strongly interacted with each other. xT scaling measurements to find the underlying physics.


CERN-ISR Discoveries, cont’dCERN-ISR Discoveries, cont’d• direct lepton (e) production from the decay of (unknown at that time-1974) particles composed of b and c quarks.

• first and only J/Psi cross section measurement for all pair pT 0 at a hadron collider, until PHENIX at RHIC [PRL 92 (2004) 051802] and CDF [PRD 71(2005) 032001 (15 years after their first publication)]• direct photon production

J/Psi suppression has been the gold plated signature for the quark gluon plasma in AAJ/Psi suppression has been the gold plated signature for the quark gluon plasma in AA


Three things are dramatically different in Three things are dramatically different in Relativistic Heavy Ion Physics Relativistic Heavy Ion Physics

than in p-p physicsthan in p-p physics• the multiplicity is ~A~200 times larger in AA central collisions than in p-p huge energy in jet cone: 300 GeV for R=1 at sNN=200 GeV• huge azimuthal anisotropies which don’t exist in p-p which are interesting in themselves, and are useful, but sometimes troublesome. • space-time issues both in momentum space and coordinate space are important in RHI : for instance what is the spatial extent of parton fragmentation, is there a formation time/distance?


High Energy Nucleus-Collisions provide the High Energy Nucleus-Collisions provide the means of creating Nuclear Matter in conditions means of creating Nuclear Matter in conditions

of Extreme Temperature and Densityof Extreme Temperature and Density

• At large energy or baryon density, a phase transition is expected from a state of nucleons containing confined quarks and gluons to a state of “deconfined” (from their individual nucleons) quarks and gluons covering a volume that is many units of the confinement length scale.


One Big GrapeOne Big Grape

(1 - e-r)/r

Rep. Prog. Phys. 63 (2000) 1511


The Quark Gluon Plasma (The Quark Gluon Plasma (QQGGPP))

• The QCD confinement scale---when the string breaks---is order:

1/QCD ~1/m=1.4 fm

• The QCD potential becomes screened with increasing temperature, T, in analogy to increasing Q2: s(T) becomes smaller, reducing the binding energy, and the string tension (T) becomes smaller, increasing the confinement radius.

• For r < 1/ a quark does feel the full color charge but for r >1/ the quark is free of the potential, effectively deconfined

V= -4 s + r -4 s e-(T)r + (1 - e-(T)r )

3 r 3 r (T)


DATA: CCOR NPB 209, 284 (1982)

ICHEP-Paris1982: first unbiased jet (UA2) ICHEP-Paris1982: first unbiased jet (UA2) +first measurement of QCD subprocess angular +first measurement of QCD subprocess angular

distribution using distribution using 00--00 correlations (CCOR) correlations (CCOR)

QQCCDDp-p


AuAu Central Collisions cf. p-pAuAu Central Collisions cf. p-pSTAR-Jet event in pp STAR Au+Au central

High pT particle

p+p

High pT particle

Au+Au

PHENIX Au+Au central

4%

0.5%


Anisotropic (Elliptic) Transverse Flow--an Anisotropic (Elliptic) Transverse Flow--an Interesting complication in AA collisionsInteresting complication in AA collisions

px

py

• spatial anisotropy momentum anisotropy

x

yz

Reaction Plane

x

y

p

patan=φ

•Perform a Fourier decomposition of the momentum space particle distributions in the x-y plane

v2 is the 2nd harmonic Fourier coefficient

Directed flow zero at midrapidity

Elliptical flow dominant at midrapidity


Elliptic Flow vElliptic Flow v22 in AuAu Central 200 GeV in AuAu Central 200 GeV Universal in constituent quark Kinetic EnergyUniversal in constituent quark Kinetic Energy

large v2 for high and low pT, plateaus for pT>2 GeV/c for mesons, scales in KE/constituent quark -meson (not shown) follows same scaling: further implies flow is partonic not hadronic KE scaling suggests Hydrodynamic origin. v2 for pT>2 GeV/c suggests low viscosity,

D.Teaney, PRC68 (2003) 034913, ``the perfect fluid’’??

STAR-PRC72 (2005) 014904 PHENIX PRL98 (2007) 162301


19% norm uncertainty

p-p collisions at RHIC: p-p collisions at RHIC: 00 production (PHENIX) production (PHENIX)

€

e−5.6 pT

No surprise (to me) that NLO pQCD agrees with dataarXiv:0704.3599v1 [hep-ex]


CCR at the CERN-ISRCCR at the CERN-ISRDiscovery of high pDiscovery of high pTT 00 production in p-p production in p-p

• e-6pT breaks to a power law at high pT with characteristic s dependence• Large rate indicates that partons interact strongly (>> EM) with other.• Data follow xT=2pT/s scaling but with neff=8!, not neff=4 as expected for QED

F.W. Büsser, et al., CERN, Columbia, Rockefeller Collaboration Phys. Lett. 46B, 471 (1973)

Bjorken scaling PR179(1969)1547 BermanBjKogut scaling PRD4(71)3388 Blankenbecler, Brodsky, Gunion xT=2pT/s Scaling PL 42B, 461 (1972)

neff gives the form of the force-law between constituents: neff=4 for QED


CCOR 1978--Discovery of CCOR 1978--Discovery of “REALLY high p“REALLY high pTT>7 GeV/c” at ISR>7 GeV/c” at ISR

CCOR A.L.S. Angelis, et al, Phys.Lett. 79B, 505 (1978)

neff=5 (=4++) as predicted for QCD

QCD: Cahalan, Geer, Kogut, Susskind, PRD11, 1199 (1975)

8

5


CCRS-1974 Discovery of direct CCRS-1974 Discovery of direct ee~10~10-4-4 at ISR at ISR not due to internal conversion of direct photonsnot due to internal conversion of direct photons

CCRS PLB53(1974)212; NPB113(1976)189 Data points (e++e-)/2 lines 10-4 (++-)/2

Farrar and Frautschi PRL36(1976)1017 proposed that direct leptons are due to internal conversion of direct photons with /~10-20% to e+e- (d/dm~1/m) for pT>1.3 GeV/c. CCRS looks, finds very few events, sets limits excluding this.

p.s. these direct e are due to semi-leptonic decay of charm particles not discovered until 1976, 2 year later: Hinchliffe and Llewellyn-Smith NPB114(1976)45


J/Psi and direct J/Psi and direct ee

CSZ NPB142(1978)29 pT=1.100.05 GeV/c

CCRS NPB113(1976)189 direct e not due to J/

First Best Not cause of direct e

CCRS PLB56(1975)482 2nd J/ in Europe


Correlations pTtrig>6 GeV/c

ISR direct photon production + correlationsISR direct photon production + correlationsSee the classic paper of Fritzsch and Minkowski, PLB 69 (1977) 316-320

q

qg

q

q g

isolatedphotonsCompton

Annihilation

Cross Section

/0

No evidence for bremss. contribution to direct --same side correlation is zero--see CMOR NPB327, 541 (1989) for full list of references.


From ISR to RHICFrom ISR to RHIC


p-p

ISR ISR 00 vs RHIC p-p vs RHIC p-p RHIC pp vs AuAu RHIC pp vs AuAu

Nuclear Modification Factor

0 are suppressed in Au+Au eg 200 GeV

€

RAA ( pT ) =d2NAA

π /dpT dyNAAinel

TAA d2σ ppπ /dpT dy0 invariant cross section in p-p at s=200 GeV is a

pure power law for pT > 3 GeV/c, n=8.10.1


Suppression of Suppression of 00 is arguably the major is arguably the major discovery at RHIC. Energy loss in medium?discovery at RHIC. Energy loss in medium?

Au Au sNN=200 GeV-QM 2005

Non-identified h and 0 different pT<6GeV/c. Does either obey QCD? xT scaling AuAu 200 cf 130 GeV showed 0 xT scaling Energy loss scales. h do not xT scale: baryons not suppressed

for 2 < pT < 6 GeV/c--This is called the baryon anomaly, still not understood.

NO suppression in A+A collisions at lower c.m. energies. Suppression is unique at RHIC-different from low sNN

Original 0 discovery, PHENIX PRL 88 (2002)022301; latest preprint nucl-ex/0611007

€

RAA ( pT ) =d2NAA

π /dpT dyNAAinel

TAA d2σ ppπ /dpT dy


NA50 at SPS (0<y<1)PHENIX at RHIC (|y|<0.35)

Bar: uncorrelated errorBracket : correlated errorGlobal error = 12% is not shown

• RAA vs. Npart integrated over pT

NA50 at SPS

• 0<y<1 PHENIX at RHIC

• |y|<0.35

BUT-J/BUT-J/ Suppression--R Suppression--RAAAA is the is the samesame for for

PHENIX mid-rapidity (e+e-) as at lower PHENIX mid-rapidity (e+e-) as at lower ssNNNN!!!!!!

PHENIX nucl-ex/0611020 to appear PRL

This was CERN-Heavy Ion’s main claim to fame in the infamous press conference of 2000 claiming observations ``consistent with the predicted signatures of a QGP.’’ Will have to wait for LHC to find out whether J/ merely act like ordinary hadrons low pT or whether they are actually probes of deconfinement as predicted by Matsui and Satz PLB178(1986)416. Also see discussion by MJT in Rep.Prog.Phys. 69 (2006)2005

Au+Au


Direct Direct 's in p-p 's in p-p s=200 GeV: Data vs. pQCD s=200 GeV: Data vs. pQCD

Published results 3<pT<15 GeV/c

PHENIX PRL 98 (2007) 012002

p-pp-p

Preliminary results for 5<pT<24 GeV/c


Aurenche et al Eur. Phys. JC9 (1999)107

PHENIX data clarifies

longstanding data/theory puzzle

Comparison with other data and pQCDComparison with other data and pQCD

Talk by Monique Werlen at RHIC&AGS users meeting 2005


<TAB>

2004--Direct Photons in Au+Au 200 GeV: follow T2004--Direct Photons in Au+Au 200 GeV: follow TABAB scaling from p-p for all centralities-no suppressionscaling from p-p for all centralities-no suppression

Direct photons unaffected by QCD medium in Au+Au

0 suppression is medium effect

1) Proves that initial state Au structure function is simply a superposition of p-p structure functions including g(x).

PHENIX PRL94 (2005) 232301

gAu+Au

Centrality


QM2005-direct QM2005-direct in AuAu via internal in AuAu via internal conversionconversion

Kroll Wada PR98(1955) 1355q

g q

e+

e-PHENIX NPA774(2006)403

Eliminating the 0 background by going to 0.2<mee<0.3 GeV enables direct signal to be signal to be

measured for 1<pmeasured for 1<pTT <3 GeV/c in Au+Au. It is exponential, does that mean it is thermal. We <3 GeV/c in Au+Au. It is exponential, does that mean it is thermal. We

must see whether p-p direct must see whether p-p direct is gaussian as p is gaussian as pTT 0 as in Drell-Yan or exponential like for 0 as in Drell-Yan or exponential like for 0


Direct are not suppressed. 0 and suppressed even at high pT

Implies a strong medium effect (energy loss) since not affected. Suppression is flat at high pT. Are data flatter than theory?

Status of RStatus of RAAAA in AuAu at in AuAu at ssNNNN=200 GeV QM05=200 GeV QM05

MJT


QM2006-Direct eQM2006-Direct e in Au+Au indicate a theoretical crisis in Au+Au indicate a theoretical crisis

heavy quarks suppressed the same as light quarks, and they flow, but less. This disfavors the energy loss by gluon bremsstrahlung in medium hypothesis but brings string theorists into the game.

p-p beautiful agreement of e with c b production PHENIX PRL97(2006)252002

Au+Au PHENIX PRL 98 (2007)172301

Au+Aup-p


RRAAAA 00 in AuAu in AuAu ssNNNN=200 GeV vs. Reaction Plane =200 GeV vs. Reaction Plane to probe details of the theory-learn something new!to probe details of the theory-learn something new!

L

PHENIX nucl-ex/0611007

(submitted to Phys. Rev. C.)

Little/no energy loss for L< 2 fm

L = distance from edge to center of participants calculated in Glauber model

RAA is absolute, v2 is relative so no hint of this in v2 measurements. This result also suggests that v2 for pT>2GeV/c is due to anisotropic energy loss not flow.RAA() vs. centrality varies density

of and distance through medium


The biggest result at QM2006??!The biggest result at QM2006??!

QM2006-QM2006-pp dir pp dir reference is run 5 msmt reference is run 5 msmt If RIf R

AAAA= R= RAA AA the whole concept the whole concept

of energy loss changes: perhaps of energy loss changes: perhaps no effect for pno effect for pTT>20 GeV >20 GeV

QM2005QM2005-I wanted to make a T-shirt-I wanted to make a T-shirtpp dir pp dir reference is pQCD reference is pQCD

€

RAA ( pT ) =d2NAA

π /dpT dyNAAinel

TAA d2σ ppπ /dpT dy


Eskola et al. NPA696 (2001) 729

gluons in Pb / gluons in p

x

AntiShadowing

Shadowing

For Au+Au min bias direct For Au+Au min bias direct R RAAAA is simple is simpleAu+Au minimum bias

Do the structure function ratios actually drop by ~20% from x=0.1 to x=0.2?

Eskola,Kolhinen,Ruuskanen Nucl. Phys. B535(1998)351

100 xT


Central Collisions---no theory counterpart-yetCentral Collisions---no theory counterpart-yetAu+Au Central Collisions

Nobody has seriously measured nor calculated structure function ratios as a function of centrality!!!

Theorists, HELP!

100 xT

Very few attempts so far for structure function measurements or theory as a function of impact parameter: E665, ZPC 65, 225 (1995) Li and Wang, PLB 527, 85 (2002) Klein and Vogt PRL 91, 142301 (2003) Emel’yanov, et al. PRC 61, 044904 (2000) and references therein.

Experimentalists: RHIC p+A, eRHIC


2-particle correlations AuAu at intermediate p2-particle correlations AuAu at intermediate pTT are very are very

different from p-pdifferent from p-pStatus at QM05: PHENIX PRELIMINARY

Is there a ’dip’ at the away-side?

Strong away-side broadening seen at low pT,assoc

Also note: systematic uncertainties should not be disregarded

2.5 < pT,trigger < 4.0 GeV1.0 < pT,assoc < 2.5 GeV

Conical emission: Mach cone? Cherenkov? Other mechanisms?

PHENIXPRL97(2006)052301

Au+Au


AuAu 200 0-5% like sign0.2< pT,1 pT,2< 0.4 GeV/c

Latest PHENIX Result-PRL June 1, 2007Latest PHENIX Result-PRL June 1, 2007

D

Away side distribution much wider in A+A than p-p in correlation fn. C() Subtraction of v2 (flow?) effect J() causes a dip at 180o which gives 2 peaks at D~1 radian independent of system and centrality for Npart >100. This is also seen for (auto) correlations of low pT particles. Is this the medium reaction to the passage of a color-charged parton? Stay tuned, much more study needed.


Away-side yield vs pAway-side yield vs pTaTa/p/pTtTt is steeper in Au+Au than p-p is steeper in Au+Au than p-p

indicating energy loss AND learn something new in p-pindicating energy loss AND learn something new in p-p

h(3<pTt<4 GeV/c)--h

Measured ratio of particle pTa/pTt xE Ratio of jet transverse momenta

€

ˆ p Ta / ˆ p Tt ≡ ˆ x h

in Au+Au indicates that away jet has lost energy relative to trigger jet.

€

ˆ x h = 0.66 ± 0.04

The away side pTa/pTt xE distribution triggered by a leading particle with pTt was thought to be equal to the fragmentation function but we found that it is NOT sensitive to the shape of the fragmentation function but only to the shape of the inclusive pTt spectrum with power n (=8.1). Formula derived in PRD 74 (2006) 072002 works for pp and AA


Many discoveries at Many discoveries at RHIC RHIC

Lead to many new Lead to many new open questions open questions

Like at the ISR in Like at the ISR in the early 1970’sthe early 1970’s


Feynman, Field and Fox said that xFeynman, Field and Fox said that xEE distribution from distribution from

single particle or Jet measures D(z)-we found not truesingle particle or Jet measures D(z)-we found not true

“There is a simple relationshipbetween experiments done with single-particle triggers and those performed with jet triggers. The only difference in the opposite side correlation is due to the fact that the ‘quark’, from which a single-particle trigger came, always has a higher p than the trigger (by factor 1/ztrig). The away-side correlations for a single-particle trigger at p should be roughly the same as the away side correlations for a jet trigger at p (jet)= p (single particle)/ <ztrig>”.

FFF Nucl.Phys. B128(1977) 1-65


As measured at the ISR by Darriulat, etc.As measured at the ISR by Darriulat, etc.P. Darriulat, et al, Nucl.Phys. B107 (1976) 429-456

Figures from P. Darriulat, ARNPS 30 (1980) 159-210 showing that Jet fragmentation functions in p, e+e- and pp (CCOR) are the

same with the same dependence of b (exponential slope) on “ ”

€

ˆ s


PHENIX-compared measured xPHENIX-compared measured xEE distribution to numerical distribution to numerical

integral using LEP fragmentation functions-not sensitive!integral using LEP fragmentation functions-not sensitive!

• independent of pTt

See M. Jacob’s talk EPS 1979 Geneva

xE ~ pTa/pTt ~z/<ztrig>

<ztrig>=0.85 measured

Dq

(z)~e-6z

ISR-CCOR

LEP

PHENIX PRD 74 (2006) 072002


ExtrasExtras


d+Au is it CGC?d+Au is it CGC?`Monojets’? `Monojets’? correlations correlations

widths and conditional yields the same for triggers in all 3 spectrometers for pp and dAu

trigger

away

PHENIX PRL 96 (2006) 222301


• Many new Explanations.

• One example:Grandchamp, Rapp, Brown; PRL 92, 212301 (2003)

In-media dissolution

Plus regeneration from

“off-diagonal” c-cbar pairs

screening

regeneration

sum

J/J/ Suppression--My Nightmare Scenario Suppression--My Nightmare Scenario

The Nightmare is that nobody will believe this. Must see J/ enhancement to believeWait for LHC result


Direct photon production-simple theory hard experimentDirect photon production-simple theory hard experiment

See the classic paper of Fritzsch and Minkowski, PLB 69 (1977) 316-320

q

qg

q

q g

isolatedphotons

Compton

Annihilation

small-ignore

Compton distribution is much flatter than scattering and peaked backwards from gluon

Substitution and Jacobean gives:


xxTT scaling scaling ssNNNN=200/130 AuAu shows h=200/130 AuAu shows h are anomalous are anomalous

• 0 xT scales in both peripheral and central Au+Au with same value of n=6.3 as in p-p. Indicates that structure and fragmentation fns. (including any energy loss) scale in AuAu i.e. energy loss is fractional. Note: a constant fractional energy loss and a power law spectrum implies that RAA=constant as observed!

• (h+ + h-)/2 xT scales in peripheral same as p-p but difference between central and peripheral is significant

PHENIX, PRC 69, 034910 (2004)


This is the Baryon Anomaly 2<pThis is the Baryon Anomaly 2<pTT<4.5 GeV/c <4.5 GeV/c

p are not suppressedp/ ratio much larger than from jet fragmentation

PHENIX PRL 91(2003) 172301

Is this ‘recombination’ QGP: Fries,Muller, Nonaka PRL 90 202303 (2003)


One of the few definitive resultsOne of the few definitive results

Trigger mesons and baryons in the region of the baryon anomaly both show the same trigger (near) side and away side jet structure. This ‘kills’ the elegant recombination model of the baryon anomaly

PHENIX PRC 71 051902 2.4<pTt<4 GeV/c 1.7< pTa<2.5 GeV/c


Near side and away side correlations the Near side and away side correlations the same for meson and baryon triggerssame for meson and baryon triggers

doi:10.1016/j.physletb.2003.10.071http://dx.doi.org/

PHENIX PLB (2007) in press


For Au+Au min bias direct For Au+Au min bias direct R RAAAA is simple is simple

100 xT

Au+Au minimum bias

Do the structure function ratios actually drop by ~20% from x=0.1 to x=0.2?

Eskola,Kolhinen,Ruuskanen Nucl. Phys. B535(1998)351


PHENIX QM2006-AuAu hPHENIX QM2006-AuAu h (3<p(3<pTtTt<4 GeV/c)<4 GeV/c) -h -h

p+p pTt=3.3 N=0.45 =1.0

AuAu00-20 N=1.25 =0.65

€

ˆ x h

€

ˆ x h


PHENIX QM2006-Chun Zhang AuAuPHENIX QM2006-Chun Zhang AuAu

p+p pT=4.4 data*1.0 fit*0.35 =1.10

AuAu00-20 data*1.0 fit*1.25 =0.45

€

ˆ x h

€

ˆ x h


PHENIX QM2006-Chun Zhang AuAuPHENIX QM2006-Chun Zhang AuAu

p+p pT=2.3 data*1.0 fit*0.35 =1.30

AuAu00-20 data*1.0 fit*5.25 =0.60

€

ˆ x h

€

ˆ x h

• pp curve is too flat at this low pT ???

• All AuAu curves roughly a factor two smaller . for central Au+Au than p-p indicating energy loss of away jet relative to trigger.

• For CuCu central the ratio is 2/3 rather than 1/2.

€

ˆ x h


Also--PHENIX QM2006-JJia Cu+CuAlso--PHENIX QM2006-JJia Cu+Cu

p+p data*1.0 fit*0.5 =0.90

CuCu60-89 data*1.0 fit*0.7 =0.70

CuCu00-20 data*1.0 fit*0.7 =0.57

€

ˆ x h

€

ˆ x h

€

ˆ x h

0 (pTt>5 GeV/c)--h


““Mike, is there a ‘real collider detector’ Mike, is there a ‘real collider detector’ at RHIC?”---J. Steinberger at RHIC?”---J. Steinberger

• PHENIX is picturesque because it is not your father’s solenoid collider detector

• Special purpose detector designed and built to measure rare processes involving leptons and photons at the highest luminosities. possibility of zero magnetic field on axis minimum of material in aperture 0.4% Xo

EMCAL RICH e i.d. and lvl-1 trigger• 0 separation up to pT ~ 25 GeV/c• EMCAL and precision TOF for h pid


PHENIXPHENIX


h

(0)

Detecting electrons means Detecting electrons means detecting all particles=PHENIXdetecting all particles=PHENIX

EMC Energy / Momentum

All charged tracks

Background

Net signalReal

Apply RICH cut

• ElectroMagnetic Calorimeter measures Energy of photons and electrons• reconstructs 0 from 2 photons. Measures decent Time of Flight • hadrons deposit Minimum Ionization, or higher if they interact

• For electron ID require RICH (cerenkov) and matching energy in EMCal

• momentum +TOF=charged particle ID• High Resolution TOF completes the picture giving excellent charged hadron PID

• Electron and photon energy can be matched to < 1%--No nonlinearity problem


PHENIX J/PHENIX J/ peaks in Au+Au peaks in Au+Au ssNNNN=200 GeV=200 GeV


Two-spin Asymmetry ATwo-spin Asymmetry ALLLL of of 00 at mid-rapidity constrains at mid-rapidity constrains

integrated gluon spin structure function integrated gluon spin structure function G of protonG of proton

PHENIX arXiv:0704.3599v1 [hep-ex] Subm. PRD Rapid Comm

phenix hcp2007m. j. tannenbaum 1/35 measurements of hard-scattering by phenix at rhic m. j....

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qcd potential

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qcd confinement scale

high energy nucleuscollisions

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