Studying the QuarkGluon Plasma in the...
Transcript of Studying the QuarkGluon Plasma in the...
Johanna Stachel
Studying the QuarkGluon Plasma in the Laboratory
historic remarks accelerators and experiments selection of a few key observables
hadron production and statistical modelshigh pt characteristics
jet quenching azimuthal correlationsheavy quarks quarkonia
conclusions and outlook
Johanna Stachel
asymptotic freedom: D.J. Gross, F. Wilczek, Phys. Rev. Lett. 30 (1973) 1343 H.D. Politzer, Phys. Rev. Lett. 30 (1973) 1346
asymptotic QCD and deconfined quarks and gluons at high T or density: J.C. Collins, M.J. Perry, Phys. Rev. Lett. 34 (1975) 1353 N. Cabibbo, G. Parisi, Phys. Lett. B59 (1975) 67
first perturbative corrections to ideal gas by Baym, Chin 1976, Shuryak 1978 ....
by 1980 new phase was called QuarkGluon Plasma (QGP): excitations are quark and gluon quasiparticles plus collective 'plasmon' modes similar to usual QED plasma
Historic Remarks
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Equation of State in Lattice QCD
(from F. Karsch, heplat/0106019)
ideal gas limit
energy density
temperaturefor 2 flavor (≅2+1): Tc = 173 ± 15 MeV
c = 0.7 GeV/fm3
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Accelerators where ultrarelativistic nuclei collide
19872000 since 2000 from 2007
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At a special seminar on 10 February, spokespersons from the experiments on CERN's Heavy Ion programme presented compelling evidence for the existence of a new state of matter in which quarks, instead of being bound up into more complex particles such as protons and neutrons, are liberated to roam freely.
nothing know yet about properties of new state
Press Release Feb. 2000: New State of Matter created at CERN
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heavy ion collider RHIC – dedicated machine
RHIC experiments: 2 large and 2 small
about 1.5 nb1 for AuAu reached in 04 run
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STAR event display
in central AuAu collsionsat RHIC √s = 200 GeV
about 7500 hadronsproduced (BRAHMS)
about three times as much as at CERN SPS
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RHIC results from first 3 years
results summarized in 4 large papers: Nuclear Physics A757 (2005)
see: nuclex/0410003 (PHENIX) nuclex/0410020 (BRAHMS)nuclex/0410022 (PHOBOS)nuclex/0501009 (STAR)
and references therein
see also BNL press release April 18, 2005:RHIC Scientists Serve Up “Perfect “ LiquidNew state of matter more remarkable than predicted – raising many new questions
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initial energy density from transverse energy
from transverse energy rapidity density using Bjorken formula:dEt/dR2) using Jacobian ddz=
SPS 158 A GeV/c AuAu collisions: dEt/dGeV 1 fm/c 0 = 3 GeV/fm3
PHENIX & STAR central AuAu collisions: dEt/dGeVnuclex/0407003 and nuclex/0409015conservatively: 1 fm/c 0 = 5.5 GeV/fm3
(factor 2 higher than at SPS top energy) optimisticallyQs = 0.14 fm/c 0 = 40 GeV/fm3
in any case this appears significantly above critical energy densityfrom lattice QCD of 0.7 GeV/fm3
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0 1 2 3 4 5rapidity
identified particles over large range in rapidity
nuclex/0403050BRAHMS
Gaussians of similar width:dominance of longitudinalexpansion
stat. model analysis requiresmidrapidity data
similarly at SPS:between 5 differentexperiments a comprehensive data setof midy hadron yields
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Analysis of yields of produced hadronic species in statistical model
from AGS energy upwards all hadron yields in central collisions of heavy nuclei reflect grand canonical equilibration strangeness suppression known from pp and e+e is lifted
for a recent review: BraunMunzinger, Stachel, Redlich,QGP3, R. Hwa, ed. (Singapore 2004) nuclth/0304013
Fit at eachenergyprovidesvalues forT and b
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P. BraunMunzinger, D. Magestro, K. Redlich, J. Stachel, Phys. Lett. B518 (2001) 41A. Andronic, P. BraunMunzinger, K. Redich, J. Stachel, Nucl. Phys. A772 (2006) 167
chemical freezeout at: T = 165 ± 5 MeV
Hadron yields at RHIC compared to statistical model
130 GeV data in excellent agreement with thermal model predictions
prel. 200 GeV data fully in linestill some experimental discrepancies
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P. BraunMunzinger, J. Stachel, J. Phys. G. 28 (2002) 1971 chem. freezeout at constant total baryon density or energy density 0.5 GeV/fm3
Note: for B < 300 MeV, LQCD phase boundary coincideswith freezeout curve
hadrochemical freezeout points and the phase diagram
how is equilibrium achieved?why freezeout at phase boundary?
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rapid hadrochemical equilibration at phase boundary
Lattice QCD calcs. F. Karsch et al.
Known since years: twobody collisions are not sufficient to bring multistrange baryons into equilibrium. The density of particles varies rapidly
with T near the phase transition. Multiparticle collisions are strongly
enhanced at high density and lead to chem. equilibrium very near to Tc.
P. BraunMunzinger, J. Stachel, C. WetterichPhys. Lett. B596 (2004) 61nuclth/0311005
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P. BraunMunzinger, J. Stachel, C. WetterichPhys. Lett. B596 (2004) 61nuclth/0311005
rate of change of density due to multiparticle collisions n(T)nin M example: for small b, reactions such as
KKKNbar bring multistrange baryons close to equilibrium. Equilibration time T60 ! similarly for all other hadron species All particles freeze out within a very narrow temperature window close to Tc.
chemical freezeout takes place at Tc
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PRL 91 (2003) 072305 and 241803
at high pt: spectra suppressed in AuAu relative to pp
proton data scaled to AuAu with appropriate number of binary collisions
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D. d’Enterria
Suppression predicted due to energy loss of partons in hot matter “jet quenching”
all expts. see largesuppression in AuAu
0 lower than h±
no suppression in dAurather Cronin enhancementmedium effect, not incoming partons
RAA=yield(AuAu)/Ncoll yield(pp)
●
hadrons
leading particle
hadrons
leading particle
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H. Baier, Y.L. Dokshitzer, A.H. Mueller, S. Peigne, D. Schiff, Nucl. Phys. B483 (1997) 291 and 484 (1997) 265energy loss of high energy parton traversing color charged medium > medium induced gluon radiationin high energy limit E s 2L2/ (1 + O(1/N))
implemented in models in different ways: high initial densities dNg/dy=1100 (Vitev/Gyulassy)large opacities <n> = L/ 34 (Levai et al.)transport coefficients q0=3.5 GeV/fm2 (BDMPS, Arleo)plasma temperature T = 400 MeV (G. Moore)medium induced ratiative energy loss dE/dx(expanding)=0.25 GeV/fm or dE/dx(static source)=14 GeV/fm (S.N.Wang)
Suppression predicted due to energy loss of partons in hot matter “jet quenching”
Johanna Stachel
suppression of hadron yields at high pt in central AuAu collisions
AuAu compared to pp scaled with number of binary collisions
in central collisions hadron yields suppressedbut not photons!
indicative of jet quenching due to partonenergy loss due to high gluon density
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Role of scattering in parton energy loss
inspired by success of softcolorinteraction model for diffractive DIS at HERA (Ingelman et al., PLB366 (1996) 371, Hoyer at al., PRD71 (2005) 074020)
soft color interactions between partons after perturbative hard interactions and before hadronization
color exchange between partons and small momentum transfer describes rapidity gaps, leading baryons, diffractive jets, high pt J/',
apply this approach to parton traversing QGP, modelled by medium of space and time dependent high gluon density
parton from hard scattering scatters with gluons of QGP, successive scatterings can lead to significant energy loss
independent hadronziation of two ends of string due to QGP implemented in PYTHIA
K. Zapp, G. Ingelman, J. Rathsman, J. Stachel, PLB637 (2006) 179
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the SCI Jet Quenching Model for QGP
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The SCI Jet Quenching Model: Parameters
if parton from hard interaction encounters a QGP gluon within a certainradius it will scatter with probablity 0.5 (0.75) if it is a quark (gluon) scattering cross section
eff= 1.9 mb
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Number of scatterings and energy loss per scattering
energy loss most efficient forintermediate pt
75
2
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SCI jet quenching model and data as function of centrality
data: PHENIX, PRL91 (2003) 072301
for most central collisions model
accounts for half of exp. effect
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data show linear dependence of RAA as function of fraction of geo. cross section
nominal cross section
cross section chosen to reproduce most central data
Centrality dependence of jet quenching
difficult to reproducein model
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RAA at lower beam energies
√s dependence of RAA consistent w/ parton Eloss models (ΔEloss~ dN/dy) + Bjorken expansion:
RAA ~ 1 @ √s~20 GeV (dNg/dy~400)RAA ~ 0.3 @ √s~62 GeV (dNg/dy~650)RAA ~ 0.2 @ √s~200 GeV (dNg/dy~1100)
“Jet quenching” model+ 1D longitudinal plasma expansionQu Wang & X.N.Wang (nuclth/0410049)
[D.d'Enterria , Hard Probes'04 Proceedings]
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2000350018231904007108500.2 LHC
80012006714203804000.6RHIC
2003501.421.52.52102400.8 SPS0[ ]fmτ [ ]T MeV [ ]tot fmτ3[ / ]GeV fmε /gdN dy
•Consistent estimate with hydrodynamic analysis
jet quenching indicative of gluon rapidity density
I. Vitev, JPG 30 (2004) S791SPS RHIC LHC
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trigger particle: 46 GeV/c correlated with all others with pt=24 GeV/c
STAR: PRL 91 (2003) 072304
Azimuthal correlations of high pt particles disappearance of awayside peak
very similar effect seen already at √s = 17.2 GeV
CERES/NA45 PRL92 (2004) 032301
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Azimuthal correlations in SCI jet quenching model
awayside peak is suppressed, but not nearlyas much as in data
general problem of model: to reproduce thiseffect need huge cross section of opacity
Johanna Stachel TB Feb.1,2005
mean pt in cone opposite to leading trigger particle
STAR nuclex/0504011
√s = 200 GeV Au+Au results:
NN Closed symbols ⇔ 4 < pTtrig < 6 GeV/c
Open symbols ⇔ 6 < pTtrig < 10 GeV/c {
{Assoc. particles: 0.15 < pT < 4 GeV/c
for central collisionsmean pt on opposite sidelooks nearly thermalized
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Heavy quark distributions from inclusive electron spectra
model all contributions from hadron decays and photon conversions using data as inputsubtraction: leaves D and B semileptonic decays
surprize: suppression very similar to pionsprediction (Dokshitzer, Kharzeev) less
energy loss for heavy quarks (dead cone eff. for radiation)
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STAR and PHENIX findings agree – using basically same method
STAR Preliminary
with EMCal even higher pt reach
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SCI jet quenching for heavy quarks
charm contribution indeedsuppressed as much as pionsbut adding beauty data are
not reproduced
compute in model the measured quantity (K. Zapp)
standard
to match pion data
Heavy Quark Energy Loss: theory vs. data
radiative only(c+b) e→
radiative + collisional (c+b) e→
radiative + collisional c e→
Where is the contribution from
beauty?Join discussion session on
parton energy loss tonight!!!
STAR Preliminary
talk P. Djawotho, STAR, Hard Probes 2006 conference
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Charmonia as QGP signature
T. Matsui and H. Satz (PLB178 (1986) 416) predict J/ suppression in QGP due to Debye screening
significant suppression seen in central PbPb at top SPS energy (NA50)in line with QGP expectations
but: at hadronization of QGP J/ can form again from deconfined quarksin particular, if number of cc pairs is large (colliders) N
J/ N
cc2
(P. BraunMunzinger and J. Stachel, PLB490 (2000) 196)statistical hadronization, charmed hadrons can equilibrate chemically
similar to production of multistrange baryons, (BraunMunzinger, Stachel, Wetterich, nuclth/0311005, Phys. Lett. B596 (2004) 61.)
typical reaction: DDbar + ⇒ J/expect J/suppression at low beam energy (SPS) and
enhancement at high energy (LHC)
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Quarkonia Production through Statistical Hadronization
Assume: all charm quarks are produced in initial hard scatteringnumber not changed in QGP
Hadronization at Tc following grand canonical statistical model used for hadrons with light valence quarks (fugacity to fix number of charm quarks, canonical correction factors at low beam energies)
P. BraunMunzinger, J. Stachel, Phys. Lett. B490 (2000) 196 and Nucl. Phys. A690 (2001) 119A. Andronic, P. BraunMunzinger, K. Redlich, J. Stachel, Nucl. Phys. A715 (2003) 529c andPhys. Lett. B571 (2003) 36M. Gorenstein et al., hepph/0202173; A. Kostyuk et al., Phys. Lett. B531 (2001) 225; R. Rapp and L. Grandchamp, hepph/0305143 and 0306077
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RHIC data on J/ Production
scaling with number of collisions participant scaling
data: Phenix central arms and Phenix muon arms
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Comparison of model predictions to RHIC data
predictions Andronic, BraunMunzinger,, Redlich, Stachel, Phys. Lett. B571 (2003) 36using NNLO pQCD results for open charm cross section
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New results: take into account the corona effect
Npart(b) =Ncore(b) + Ncorona(b)
Nuclear density distribution: “core” up to RA + Xc ”corona” outside
dNch/d/Npart(b) = dNch/d/Ncore(b)+ dNchpp/d/Ncorona(b)
Collisions in corona region as in pp, core: medium, e.g. QGP
relevance recently pointed out by Klaus Werner hepph/0603064
fraction of nucleons (participants) in corona: Npart=30 ↔ 55% Npart = 350 ↔ 10%
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Statistical charm hadronization and RHIC data
pp charm cross section FONLLCacciari et al., hepph/0502203cc = 256+400
146 bmeasured PHENIX cross section at upper edge of pQCD calc, STAR factor 2 higherneed experimental clarification
Falloff of data with centrality very moderate prediction based on just Debye screening much lower for central coll.
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Statistical charm hadronization and RHIC data vs rapidity
pp charm cross section FONLLCacciari et al., hepph/0502203cc = 256+400
146 b
data very well reproduced
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does charm quark recombination in QGP play a role?
study ccbar gg in expandingand cooling QGP
cross section via detailed balance from calculations ofgg ccbarby Glück, Owens, Reya, PRD 17 (1978) 2324
order of 0.1 mb
annihilation rate/volume:drcc/d = nc
2 < ccbar gg v>integrate over T evolution until Tc
annihilation appears irrelevanteven if cross section would be
factor 10 bigger
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Energy dependence of Quarkonia Production in Statistical Hadronization Model
This predicted centralitydependence is unique for
the statistical hadronizationmodel.
Its observation would not onlyimply that recombination isat work, but be a fingerprint
of deconfinement.
Upsilon at LHC expected tolook like J/ at RHIC
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Simulation of dielectron mass spectrum 1 month PbPb at ALICE
hadron yields in chemical equilibrium, due to very rapid increase in densities close to Tc drive multiparticle collisions system to equilibrium
high pt hadrons suppressed in central AuAu collisionsmedium effect, since not seen in dAujet quenching in hot medium expectedmodelling with high parton density etc. successful but still schematic
azimuthal correlations of high pt particles: disappearance of awayside peak for central AuAu collisions when pt high enoughlower partner pt: awayside peak broadened, momenta thermalized
also heavy quarks show significant jet quenchingrole of scattering vs radiative energy loss
charmonia: role of statistical recombination important, accounts well for new RHIC data
Observations after 3 years running at RHIC
we are on our way characterizing the QGP, new era with LHC
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Backup slides
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top AGS energy AuAu top SPS energy PbPb
Hadrochemistry at fixed target energies
A. Andronic, P. BraunMunzinger, K. Redich, J. Stachel, Nucl. Phys. A772 (2006) 167
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jet production in deuteron Au collisions
not suppressed butrather enhanced due to initial parton scattering
(Cronin effect)
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talk A. Dion, PHENIX, Hard Probes 2006 Conference
Peter BraunMunzinger
Comparison of charm data with pQCD
measured values much larger than pQCD predictions
Charm total cross section
∀σ=1.4±0.2±0.4 mb in minimum bias d+Au collisions at √sNN=200 GeV
∀σ=1.26±0.09±0.23 mb in minimum bias Au+Au collisions at √sNN=200 GeV
∀σ=1.33±0.06±0.18 mb in 012% Au+Au collisions at √sNN=200 GeV
• Charm total cross section obeys Nbin scaling from d+Au to Au+Au within error bars• Supports conjecture that charm is exclusively produced in initial scattering• However, the total charm cross section is ~5× larger than NLO (and FONLL) predictions!!!
talk P. Djawotho, STAR, Hard Probes 2006 conference
pQCD calculations for p+p vs. data
• All suppression predictions use the most recent pQCD calculations as starting point (p+p reference).
• Where does bottom start to dominate?– Relative contribution of charm
and bottom?– Large uncertainty in the
crossing point• From ~3 to 10 GeV/c
• From shape: significant b contribution at highpT?
STAR Preliminary
talk P. Djawotho, STAR, Hard Probes 2006 conference
Johanna Stachel
Johanna Stachel
J/ Suppression in QGP
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Npart dependence at LHC SHM prediction
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Has the QuarkGluon Plasma been seen ?
Observations that led to the CERN press release fully confirmed at RHIC (where measured)
additional features observed at RHIC; start to probe the properties of this medium (liquid, not ideal gas, large cross sections, low viscosity)
no direkt proof but i) observations cannot be explained assuming a hadronic medium ii) critical parameters well exceeded iii) many of the expected and predicted features start to show up
more data to come from high luminosity running at RHIC and with some detector upgrades (in particular involving heavy quarks, photons, dileptons)
LHC from 2007: exceed Tc by factor 5 or so, qualitatively new features expected