Chiral Symmetry Restoration and Deconfinement in QCD at Finite Temperature M. Loewe
Marcus Bleicher, Florence 2006 Longitudinal Flow and Onset of Deconfinement Marcus Bleicher Institut...
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Transcript of Marcus Bleicher, Florence 2006 Longitudinal Flow and Onset of Deconfinement Marcus Bleicher Institut...
Marcus Bleicher, Florence 2006
Longitudinal Flow and Onset of DeconfinementLongitudinal Flow and
Onset of Deconfinement
Marcus Bleicher
Institut für Theoretische Physik
Goethe Universität Frankfurt
Germany
Marcus Bleicher, Florence 2006
Outline of the talkOutline of the talk
• Introduction
• Fluctuations Evidence for mixing
• Rapidity widths + Landau softest point
• Summary
Marcus Bleicher, Florence 2006
The tool: UrQMDv2.2The tool: UrQMDv2.2
• Non-equilibrium transport model• Hadrons and resonances• String excitation and fragmentation• Cross sections are parameterized
via AQM or calculated by detailed balance• pQCD hard scattering at high energies
• Generates full space-time dynamics of hadrons and strings
Marcus Bleicher, Florence 2006
Thanks to the UrQMD group@ Frankfurt
Thanks to the UrQMD group@ Frankfurt
• Sascha Vogel (Resonances)
• Stephane Haussler (Event-by-Event Fluctuations)
• Hannah Petersen (Flow at FAIR)
• Diana Schumacher (Di-Leptons)
• Qingfeng Li (Isospin Dynamics & HBT)
• Xianglei Zhu (Elliptic Flow and Charm)
• Mohamed Abdel-Aziz (Event-by-Event Fluctuations)
• Elena Bratkovskaya (HSD)
• and Horst Stoecker (keeping it running)
Marcus Bleicher, Florence 2006
MotivationMotivation
At RHIC: look for signals of freely moving partons.
At FAIR/SPS:look for the mixed phase and the onset of deconfinement
E. Bratkovskaya, M.Bleicher. et al., PRC 2005
Marcus Bleicher, Florence 2006
Excitation functions: ratios
Excitation functions: ratios
• ‘Horn’ in the ratio not reproduced
• well reproduced
• relative strange baryon enhancement reproduced
/K
/K
/
E. Bratkovskaya, M.Bleicher. et al., PRC 2005
Marcus Bleicher, Florence 2006
• K/ fluctuations increase towards lower beam energy– Significant enhancement over hadronic cascade model
• p/ fluctuations are negative– indicates a strong contribution from resonance decays
NA49 Preliminary NA49 Preliminary
Fluctuation studies
Tak
en f
rom
Ch
risto
ph
Rol
and
Marcus Bleicher, Florence 2006
Energy dependenceEnergy dependence
H. Petersen, X. Zhu, M.B.
• Qualitative description OK
• Importance of potentials at low energies
• Lack of pressure shows up at SPS energies
• EoS <-> Flow
Marcus Bleicher, Florence 2006
‘Partonic’ dof already atlow SPS energy
‘Partonic’ dof already atlow SPS energy
•Breakdown of v2 in model coincides with onset of ‘partonic’ matter
signals onset of change of EoS in the early stage
30 AGeV
H. Petersen, X. Zhu, M.B.
Marcus Bleicher, Florence 2006
Stopping power
Stopping power
• Linear increase of rapidity shift at low energies
• ‘Saturation’ above highest SPS energy
• However, relative momentum loss is energy independent
UrQMD vs data
Pb+Pb/Au+Au
Marcus Bleicher, Florence 2006
• Multiplicities• Temperatures• Elliptic Flow• Correlations
have already been studied
Can we learn more from the longitudinal dynamics?
Marcus Bleicher, Florence 2006
Multiplicity fluctuationsMultiplicity fluctuations
Extraction of the multiplicity distribution for every Npar
Note: Calculation is narrower than the data for Npar~45
Pb+Pb (158 AGeV)
in the NA49 acceptance
(1.1<yCM<2.9)
Marcus Bleicher, Florence 2006
• The fluctuation is quantified with the
scaled variance :
• Enhanced fluctuations for mid-
peripheral collisions are observed
Multiplicity fluctuations at SPS:The problem
Multiplicity fluctuations at SPS:The problem
NNVar
NNNVar
)(
)(22
Note : - for a poisson distribution, w=1Similar results from HIJING, HSD and RQMD
Marcus Bleicher, Florence 2006
Where is the problem?Where is the problem?
Pb+Pb (158 AGeV)
in the NA49 acceptance
(1.1<yCM<2.9)• Mean value correctly reproduced
• Variance reproduced for central and very peripheral events
• Failure for mid-peripheral events
Marcus Bleicher, Florence 2006
Analysis of different windowsAnalysis of different windows
the normalized variance :
• flat in the projectile hemisphere
• larger in the mirror acceptance
• even larger in 4
• maximum around Np=40
Konchakovski, Haussler,…, PRC 73 (2006)
Marcus Bleicher, Florence 2006
Fluctutions in target regionFluctutions in target region
• the fluctuation has a maximum
around Np=25
• introduces an asymetry between
projectile and target participants
• leads to an increase of the multiplicity
fluctuation in the target hemisphere
NNVart
part
t
partt
P arg
arg
arg )(
Marcus Bleicher, Florence 2006
Correlation length in rapidityCorrelation length in rapidity
Rapidity window dependence :
• correlation length of the order of 1
unit of rapidity
• target and projectile hemisphere are
independent in hadron-string models
Marcus Bleicher, Florence 2006
Mixing and fluctuationsMixing and fluctuations
M. Gazdzicki and M. Gorenstein:arXiv:hep-ph/0511058
• I.e. the trigger condition ‘marks’ projectile and target participants
• This allows to study the degree of mixing of the matter produced in HIC
• Data suggest strong mixing of hemispheres
Hints to expanding initial fireball in contrast to string dynamics
Marcus Bleicher, Florence 2006
What the fluctuations told us…What the fluctuations told us…
• Initial fireball of newly produced particles
• Fireball seems to expand Landau-like
• Leads to strong correlations in rapidity
We might use Landau-type hydro to explore the properties of this matter
Marcus Bleicher, Florence 2006
Pion rapidity densityPion rapidity density
• Pions rapidity densities are Gaussians at all energies
D. Ouerdane, QM04D. Ouerdane, QM04
Marcus Bleicher, Florence 2006
Different particle typesDifferent particle types
• NA49 data yields Gaussian rapidity distributions
• Also ALL other experiments report Gaussians for newly produced particles
Marcus Bleicher, Florence 2006
Fireball expansionFireball expansion
• Assumptions:- applies only to newly produced particles
- Lorentz contracted nuclei
- simplified Hagedorn gas EoS
E. Shuryak, Yad. Fiz. 16 (1972) 395
similar to Landau hydro
For more praise on Landau hydro see. P. Steinberg
Marcus Bleicher, Florence 2006
Rapidity widthsRapidity widths
• Rapidity width scales linearly with projectile rapidity
M. Bleicher, hep-ph/0509314
Marcus Bleicher, Florence 2006
Speed of soundSpeed of sound
• Analysis of the rapidity data indicates a softest point at20-30 AGeV beam energy
M. Bleicher, hep-ph/0509314
Marcus Bleicher, Florence 2006
Its soft, but…Its soft, but…
• …is it the mixed phase?
• UrQMD also describes the rapidity widths
• UrQMD has a soft equation of state
Marcus Bleicher, Florence 2006
SummarySummary
• Fluctuations indicate strongly mixed initial stage
• Assumption of Landau-type hydro allows to extract speed of sound from rapidity widths
• Apparent local minimum of sound velocity around 20 – 30 AGeV
• Nature of this softest point is unclear