Excitation Functions of Hadronic Observables

1
Excitation Functions of Hadronic Observables
2
IntroductionSoft Hadron Production

• Soft physics regime
• pt lt 2 GeV/c
• Bulk properties of particle production
• Rapidity Spectra
• Stopping (net-protons)
• Longitudinal expansion
• Particle Yields
• Strangeness / pion ratio
• Transverse Mass Spectra
• Transverse expansion (? EOS?)
• Thermal freeze-out conditions
• Elliptic Flow
• v2 of pions
• Fluctuations
• K/? (p/?) fluctuations

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IntroductionExperiments
4
Rapidity Spectra Energy Dependence of Net-Protons
BRAHMS, I.G. Bearden et al. PRL 93 (2004), 102301
The shape of the distributions change
dramatically with energy
AGS baryonic system ? RHIC mesonic system
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Rapidity SpectraEnergy Dependence of ??y ?
BRAHMS, I.G. Bearden et al. PRL 93 (2004), 102301
Rapidity shift
Seems to increase linearly at AGS and SPS
??y ?/ybeam ? 0.27
But Weaker increase to RHIC energies!
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Particle YieldsRapidity Spectra of Identified
Particles
NA49 data Central PbPb 7 (20-80) 5/10 (158)
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Rapidity SpectraPions
Central PbPb/AuAu
Comparison AGS, SPS, and RHIC
Single Gaussians!
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Rapidity SpectraEnergy Dependence of Widths
Pion widths are close to Landau prediction, but
not perfectly
But Perfect agreement to linear dependence on
ybeam
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Rapidity SpectraEnergy Dependence of Widths
Linear dependence on ybeam (works up to RHIC !)
NA49 preliminary
? Thermal component of longitudinal flow
10
Particle YieldsEnergy Dependence of 4? Yields
AGS
NA49
BRAHMS
Central AuAu, PbPb
Access to the energy dependence of identified
particle yields in the range ?sNN 2.5 200
GeV
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Particle YieldsEnergy Dependence of Pion Yield
???/?Nw?
Steeper slope in AA than in pp for Ebeam gt 20A
GeV
F (GeV½)
12
Particle YieldsEnergy Dependence of Particle
Ratios
UrQMD HSD E.L. Bratkovskaya et al., PRC 69
(2004), 054907
Statistical hadron gas P. Braun-Munzinger, J.
Cleymans, H. Oeschler, and K. Redlich Nucl.
Phys. A697 (2002) 902
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Particle YieldsEnergy Dependence of ?K?/?? ?
Non-monotonic structure
Not present in pp (?) and NN (upper limit) (O)
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Particle YieldsEnergy Dependence of K/? at
Mid-Rapidity
Central PbPb/AuAu
Mid-rapidity ratios
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Particle YieldsComparison s- and s-Carriers
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Particle Yields(Anti-)Strangeness to Pion Ratio
Difficult to model in hadronic scenarios Solid
line Statistical hadron gas model with ?s 1
K. Redlich, priv. comm. Predicted as signal for
the onset of deconfinement Dotted line M.
Gazdzicki and M.I. Gorenstein, Acta Phys. Polon.
B30 (1999), 2705
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Particle YieldsAntibaryon-Baryon Ratio
Energy dependence weakens with increasing
strangeness content
NA49 preliminary
Lines Statistical hadron gas model J. Manninen
et al. Fit to 4? data!
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Particle YieldsAntilambda-Antiproton Ratio
Increase above 1 towards lower energies consisten
t with recent NA49 data
Models predict ratio lt 1
Hadron Gas 1 J. Manninen et al. Hadron Gas 2 K.
Redlich et al. Hadron Gas 3 J. Rafelski et al.
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Particle YieldsOutlook
Still some discrepancies between experiments NA57
? NA49 Ongoing activities at SPS
NA49 Energy dependence of K0s, ? (C. Strabel, T.
Schuster, M. Mitrovski) Reanalysis of ? (20A -
158A GeV)
NA45 K0s, ? (40A, 80A, 158A GeV)
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Transverse Mass SpectraEnergy Dependence of
?mt?-m0
? negatively charged
Energy dependence of transverse activity seems to
change around 30 AGeV. General feature for
pion, kaons and protons
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Transverse Mass SpectraInverse Slope Parameters
of Kaons
Y. Hama et al. Braz. J. Phys. 34 (2004), 322,
hep-ph/0309192
Feature cannot be described by transport models
Hydro calculation with assumption of 1st order
phase transition
? Change of EOS seen?
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Transverse Mass SpectraHydro - Model

• Basic model
• Common freeze-out of all particle types
• Boost invariant longitudinal expansion
• Transverse expansion is modelled by a velocity
  profile
• Standard version

Schnedermann, Sollfrank, and Heinz, Phys. Rev. C46

• Extended version
• Resonance contribution included
• Baryonic resonances introduce dependence on ?B
• Chemical freeze-out Tch and ?B taken from
  freeze-out curve
• Thermal freeze-out System cools down,
  therefore assume
• Conservation of entropy
• Conservation of effective particle numbers

U. Wiedemann and U. Heinz, Phys. Rev. C56
(1997) 3265 B. Tomasik, nucl-th/0304079
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Transverse Mass SpectraHydro Model Fits
?-
p
K-
Convave ? Resonances
Exponential
Shoulder ? Radial flow
E895 nucl-ex/0306033 NA49 Phys. Rev. C66
(2002) 054902, nucl-ex/0403023 PHENIX Phys. Rev.
C69 (2004) 024904, nucl-ex/0307022
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Transverse Mass SpectraEnergy Dependence of Fit
Parameter
Fit to ?-, K- and p
Tch
Box-shaped source profile and linear velocity
profile Fit range 0.1 lt mt-m0 lt 0.8 GeV
Energy dependence of Tf seems to change around 30
AGeV Thermal and chemical freeze-out different?
Single freeze-out model? Continous increase of
??T?
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Transverse Mass SpectraPhase Diagram Thermal
Freeze-Out
In this approach the thermal freeze-out seems to
be at lower temperature than chemical
freeze-out from top AGS energies on
Strongly model dependent ! Single freeze-out
models ?

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Elliptic FlowEnergy Dependence of v2 for Pions
Mid-rapidity data, pt integrated
Initial spatial anisotropy ? different pressure
gradients ? momentum anisotropy v2
Energy dependence changes in SPS region
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FluctuationsParticle Ratios
Event-by-event fluctuations of e.g. K/?

• Compare to mixed event
• reference
• Resolution
• Finite number statistics

NA49
? Extraction of dynamical fluctuations
NA49
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FluctuationsEnergy Dependence of K/p Fluctuations
Data wider than mixed events reference
Clear energy dependence of K/p fluctuations in
SPS energy range observed Energy
dependence different at higher energies
preliminary
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Conclusions

• Many structures in the excitation functions of
  hadronic observables in the SPS energy region
• Pions / Nw
• Strangeness / pion ratio
• Transverse mass spectra
• Elliptic flow
• K/? fluctuations
• Stopping ?
• Indication for phase transition seen?
• Still more data is coming (NA45 NA49)
• Strangeness (K0s, ?, ?)
• Net-protons (20A 80A GeV)
• Flow (20A 30A GeV)

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The End
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Rapidity SpectraKaons
Single Gaussian works reasonably well for K-
Does not really work for K at lower SPS
energies ? Use RMS
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Rapidity SpectraMass Dependence of Widths
? negatives
Approx. linear dependence on particle mass
Similar slope at all SPS energies
? Thermal component of longitudinal flow
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Particle YieldsEnergy Dependence of ? at
Mid-Rapidity
preliminary
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Particle YieldsStatistical Hadron Gas Model
Becattini et al., Phys. Rev. C69 (2004) 024905
Assumption of chemical equilibrium at the
freeze-out point
? Particle production can be described with a
few parameters V, T, ?B, ?s
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Elliptic Flowv2 for Pions, Protons, and Lambdas
Linear increase of v2 with pt for all particle
species Clear mass hierarchy v2(?) gt v2
(p) gt v2(?) Blast wave fits reproduce data quite
well T 92 MeV, ??? 0.5 Model F.
Retiere and M. Lisa, Phys. Rev. C70 (2004),
044907
NA49 data on pions and protons C. Alt et al.,
Phys. Rev. C68 (2003), 034903.
PbPb, 158 AGeV
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Elliptic FlowComparison to Hydro Model
Data below hydro calculation with Tf120MeV
Hydro calculation by Pasi Huovinen
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Transverse Mass Spectra
Central (7) PbPb
Radial flow fit (Blast Wave)
20 AGeV
30 AGeV
Here ?t independent of r
Schnedermann, Sollfrank, and Heinz, Phys. Rev. C46
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Transverse Mass Spectra
Central PbPb 4080 AGeV 7 158 AGeV 5,
10(?), 23.5(?)
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Transverse Mass SpectraThe Omega
Evidence for early freeze-out of the Omega from
blast wave fits?
NA49 publication C. Alt et al., nucl-ex/0409004
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Transverse Mass SpectraInverse Slope Parameters
of Kaons
Step in energy dependence
Seems to be absent in pp
How about other particle types?
pp compilation from M. Kliemant, B. Lungwitz,
and M. Gazdzicki, PRC 69 (2004) 044903
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Bose-Einstein CorrelationsEnergy Dependence of
Radius Parameters
No indication for strong energy dependence
between AGS and RHIC
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Bose-Einstein CorrelationsBlast Wave Model Fits
Combined fit to HBT radii and transverse mass
spectra protons and ?-, mid-rapidity
Good fit to the data slight deviations in Rside
at high kt
Blast wave model M. Lisa, F. Retiere,
nucl-th/0312024
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Bose-Einstein CorrelationsThermal Freeze-Out
Parameters
Tchem J. Cleymans, K. Redlich,
Phys. Rev. C60, 054908 (1999)
Slightly increasing temperature with beam
energy Approx. constant transverse geometrical
Radii (Rbox? 2Rgauss) Finite emission duration at
SPS energies
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NA49 AA Physics ProgramExploring the QCD Phase
Diagram

• SPS energy regime allows to explore an
  essential part of the phase diagram
• Chemical freeze-out points approach phase
  boundary at SPS energies
• Transition to QGP is likely to happen in
  this region
• Ebeam 20 - 158 AGeV (?sNN 6.3
  - 17.3 GeV)
• Use hadronic observables to pin down phase
  transition
• Systematic studies required
• ? Energy dependence

Lattice calculations Fodor and
Katz Bielefeld-Swansea group Hadron gas fits
(?) J. Manninen et al.