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

Statistical Model Predictions for p+p and Pb+Pb Collisions at LHC. Ingrid Kraus Nikhef and TU Darmstadt. Outline. Predictions for Pb+Pb collisions at LHC Extrapolation of thermal parameters, predictions Experimental observables for T and μ B determination

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

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  1. Statistical Model Predictions for p+p and Pb+Pb Collisions at LHC Ingrid Kraus Nikhef and TU Darmstadt

  2. Outline • Predictions for Pb+Pb collisions at LHC • Extrapolation of thermal parameters, predictions • Experimental observables for T and μB determination • From Pb+Pb to p+p: system size and energy dependence • Model ansatz with correlated, equilibrated clusters • Analysed data and results • Predictions for p+p collisions at LHC • Driven by initial or final state? • Summary • in Collaboration with H. Oeschler, K. Redlich, J. Cleymans, S. Wheaton Last call for predictions workshop, CERN, May 30, 2007

  3. T, Vb, Nb T, V, m 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 Last call for predictions workshop, CERN, May 30, 2007

  4. Thermal Parameters in Pb+Pb 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(√(sNN) = 5.5TeV) = 1 MeV Phys. Rev. C 73 (2006) 034905 Grand canonical ensemble for Pb+Pb predictions Last call for predictions workshop, CERN, May 30, 2007

  5. Predictions for Pb+Pb • Reliable for stable particles • Benchmark for resonances • Errors: T = 170 +/- 5 MeV μB = 1 + 4 MeV Phys. Rev. C 74 (2006) 034903 - 1 All calculations with THERMUS hep-ph/0407174 Last call for predictions workshop, CERN, May 30, 2007

  6. 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 Last call for predictions workshop, CERN, May 30, 2007

  7. 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 Last call for predictions workshop, CERN, May 30, 2007

  8. 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 Last call for predictions workshop, CERN, May 30, 2007

  9. _ T and μB dependence II: h/h ratios • Sensitive on μB • μS opposite trend of μB • determine μB from p/p • weakly dep. on T ☺ _ Last call for predictions workshop, CERN, May 30, 2007

  10. T dependence: ratios with large mass differences • Ratios with larger mass differences are more sensitive T from W / p and/or W / K ☺ Last call for predictions workshop, CERN, May 30, 2007

  11. 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 Last call for predictions workshop, CERN, May 30, 2007

  12. 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 √(sNN) = 17 AGeV Last call for predictions workshop, CERN, May 30, 2007

  13. 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 • p+p, C+C, Si+Si, Pb+Pb / Au+Au collisions • at SPS and RHIC energies R RC Last call for predictions workshop, CERN, May 30, 2007

  14. System size and energy dependence of the cluster size • Small clusters in all systems • Small system size dependence • p+p • energy dependence? • Pb+Pb / Au+Au • data consistent with saturated strangeness production p+p C+C Si+Si Pb/Au Last call for predictions workshop, CERN, May 30, 2007

  15. System size and energy dependence of the cluster size • A+A: clusters smaller than fireball • RC not well defined for RC ≥ 2 fm because suppression vanishes RC= R Pb+Pb Au+Au Last call for predictions workshop, CERN, May 30, 2007

  16. System size and energy dependence of the cluster size RC= R Pb+Pb Au+Au • Particle ratios saturate at RC ≈ 2 - 3 fm • no precise determination for weak strangeness suppression Last call for predictions workshop, CERN, May 30, 2007

  17. 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 Last call for predictions workshop, CERN, May 30, 2007

  18. System size and energy dependence of T and mB • T, μB weakly dependent on system size p+p C+C Si+Si Pb/Au Last call for predictions workshop, CERN, May 30, 2007

  19. Extrapolation to LHC: cluster size • what defines RC in p+p? • initial size of p+p system relevant • RC const • final state of large number of produced hadrons relevant • RC increases with multiplicity Last call for predictions workshop, CERN, May 30, 2007

  20. Prediction for p+p • 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 Last call for predictions workshop, CERN, May 30, 2007

  21. Extraction of RC • Particle ratios w/o strangeness are insensitive to RC • Sensitivity increases with strangeness difference RC from W / p ☺ Last call for predictions workshop, CERN, May 30, 2007

  22. Summary • p+p • predictions difficult due to unknown degree of canonical suppression • Cluster radius RC from data • Pb+Pb • predictions for particle ratios with extrapolated parameters T, μB • T, μB determination with p / p and W / K or W / p ratios _ Last call for predictions workshop, CERN, May 30, 2007

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