Statistical Model Predictions for p p and Pb Pb Collisions at LHC

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Statistical Model Predictions for pp and PbPb
Collisions at LHC

• Ingrid Kraus
• Nikhef and TU Darmstadt

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Outline

• Predictions for PbPb collisions at LHC
• Extrapolation of thermal parameters, predictions
• Experimental observables for T and µB
  determination
• From PbPb to pp system size and energy
  dependence
• Model ansatz with correlated, equilibrated
  clusters
• Analysed data and results
• Predictions for pp collisions at LHC
• Driven by initial or final state?
• Summary
• in Collaboration with H. Oeschler, K. Redlich, J.
  Cleymans, S. Wheaton

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Hadron ratios in the grand canonical ensemble

• Grand canonical ensemble
• large systems, large number of produced hadrons
• two parameters describe particle ratios in the
  hadronic final state

A. Andronic, P. Braun-Munzinger, J. Stachel,
Nucl. Phys. A772 (2006) 167
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Thermal Parameters in PbPb
Phys. Rev. C 73(2006) 034905

• On the freeze-out curve
• TLHC TRHIC 170 MeV
• T TC 170 MeV
• µB from parametrised
• freeze-out curve
• µB (v(sNN) 5.5TeV) 1 MeV
• Phys. Rev. C 73 (2006) 034905
• Grand canonical ensemble
• for PbPb predictions

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Predictions for PbPb

• Reliable for stable particles
• Benchmark for resonances
• Errors
• T 170 /- 5 MeV
• µB 1 4 MeV
• Phys. Rev. C 74 (2006) 034903

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All calculations with THERMUS hep-ph/0407174
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T and µB dependence I mixed ratios

• Controlled by masses
• Weakly dep. on µB and T
• µB term cancels
• larger contributions from resonances at higher T

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T and µB dependence I mixed ratios

• Controlled by masses
• Weakly dep. on µB and T
• µB term cancels
• larger contributions from resonances at higher T

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T and µB dependence I mixed ratios

• Controlled by masses
• Weakly dep. on µB and T
• µB term cancels
• larger contributions from resonances at higher T
• K/p
• not usable for T and mB determination
• good test of predictions

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T and µB dependence II h/h ratios
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• Sensitive on µB
• µS opposite trend of µB
• determine µB from p/p
• weakly dep. on T

?
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T dependence ratios with large mass differences

• Ratios with larger mass differences are more
  sensitive
• T from W / p and/or W / K

?
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Canonical suppression

• Canonical ensemble
• small systems / peripheral collisions, low
  energies
• suppressed phase-space for particles related to
  conserved charges
• Stronger suppression for multi-strange hadrons
• Suppression depends on strangeness content, not
  difference

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Canonical suppression

• Canonical ensemble
• small systems / peripheral collisions, low
  energies
• suppressed phase-space for particles related to
  conserved charges
• Stronger suppression for multi-strange hadrons
• Suppression depends on strangeness content, not
  difference
• Suppressed strangeness production beyond
  canonical suppression

SPS v(sNN) 17 AGeV
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Modification of the model

• Statistical Model approach T and µB
• Volume for yields ? radius R used here
• Deviations strangeness undersaturation factor gS
• Fit parameter
• Alternative small clusters (RC) in fireball (R)
  RC R
• Chemical equilibrium in subvolumes canonical
  suppression
• RC free parameter
• Study
• pp, CC, SiSi, PbPb / AuAu collisions
• at SPS and RHIC energies

R
RC
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System size and energy dependence of the cluster
size

• Small clusters in all systems
• Small system size dependence
• pp
• energy dependence?
• PbPb / AuAu
• data consistent with saturated strangeness
  production

pp CC SiSi Pb/Au
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System size and energy dependence of the cluster
size
RC R
PbPb AuAu

• AA clusters smaller than fireball
• RC not well defined for RC 2 fm because
  suppression vanishes

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System size and energy dependence of the cluster
size
RC R
PbPb AuAu

• Particle ratios saturate at RC 2 - 3 fm
• no precise determination for weak strangeness
  suppression

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Extrapolation to LHC T - mB systematics
Phys. Rev. C 73(2006) 034905

• Chemical decoupling conditions extracted from SIS
  up to RHIC feature common behavior
• Extrapolation to LHC energy with parametrisation
  e.g.
• Nucl. Phys. A 697 (2002) 902

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System size and energy dependence of T and mB

• T, µB weakly dependent on system size

pp CC SiSi Pb/Au
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Extrapolation to LHC cluster size

• what defines RC in pp?
• initial size of pp system relevant
• RC const
• final state of large number of produced hadrons
  relevant
• RC increases with multiplicity

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Prediction for pp

• significant increase of ratios at RC 1.5 fm
• K / p and W / X behave differently
• multistrange hadrons suffer stronger suppression
• RC will be determined with ALICE data

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Extraction of RC

• Particle ratios w/o strangeness are insensitive
  to RC
• Sensitivity increases with strangeness difference
• RC from W / p

?
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Summary

• pp
• predictions difficult due to unknown degree of
  canonical suppression
• Cluster radius RC from data

• PbPb
• predictions for particle ratios with extrapolated
  parameters T, µB
• T, µB determination with p / p and W / K or W / p
  ratios

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