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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 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 QGP workshop, Erice, Sept 18, 2008

  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 QGP workshop, Erice, Sept 18, 2008

  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 QGP workshop, Erice, Sept 18, 2008

  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 QGP workshop, Erice, Sept 18, 2008

  6. _ T and μB dependence I: h / h ratios • Sensitive on μB determine μB from p/p • weakly dep. on T ☺ _ QGP workshop, Erice, Sept 18, 2008

  7. T dependence: ratios with large Dm • Ratios with larger mass differences are more sensitive T from W / p and/or W / K ☺ QGP workshop, Erice, Sept 18, 2008

  8. T and μB dependence II: mixed ratios • Controlled by masses • Weakly dep. on μB and T • K/p • not usable for T and mB determination • good test of predictions QGP workshop, Erice, Sept 18, 2008

  9. 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 QGP workshop, Erice, Sept 18, 2008

  10. 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 QGP workshop, Erice, Sept 18, 2008

  11. 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 QGP workshop, Erice, Sept 18, 2008

  12. System size and energy dep. of 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 QGP workshop, Erice, Sept 18, 2008

  13. System size and energy dep. of 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 QGP workshop, Erice, Sept 18, 2008

  14. System size and energy dep. of cluster size RC= R Pb+Pb Au+Au • Particle ratios saturate at RC ≈ 2 - 3 fm • no precise determination for weak strangeness suppression QGP workshop, Erice, Sept 18, 2008

  15. 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 QGP workshop, Erice, Sept 18, 2008

  16. System size and energy dep. of T and mB • T, μB weakly dependent on system size p+p C+C Si+Si Pb/Au QGP workshop, Erice, Sept 18, 2008

  17. 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 QGP workshop, Erice, Sept 18, 2008

  18. Prediction for p+p • significant increase of ratios at RC ≈ 1.5 fm • RC will be determined with ALICE data QGP workshop, Erice, Sept 18, 2008

  19. Extraction of RC • Sensitivity increases with strangeness difference RC from W / p ☺ hep-ph 0808.0611 QGP workshop, Erice, Sept 18, 2008

  20. W / p • For Pb+Pb ratio was proposed as a measure of T but … • Sensitivity on canonical suppression is much stronger than on T QGP workshop, Erice, Sept 18, 2008

  21. 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 _ QGP workshop, Erice, Sept 18, 2008

  22. Data and fits QGP workshop, Erice, Sept 18, 2008

  23. Data and fits II QGP workshop, Erice, Sept 18, 2008

  24. Tables from paper QGP workshop, Erice, Sept 18, 2008

  25. _ Resonance Contribution to p/p • Ratio not affected by feeding • net baryon number is conserved QGP workshop, Erice, Sept 18, 2008

  26. Resonance Contribution to K and p QGP workshop, Erice, Sept 18, 2008

  27. Resonance Decays • Wno resonance contribution • X • 50% from feed-down • both exhibit same T dependence • K decay exceeds thermal at LHC • p • thermal production ≈ constant • resonance contribution dominant • 75% of all p from resonances • p/pprimary ≈ p/pdecay _ _ QGP workshop, Erice, Sept 18, 2008

  28. Sensitivity on T Relative variation of R per 1MeV change of T • Thermal • K / p and W / X have same T dependence • sensitivity increases with mass difference • Decay contribution • lighter particles are stronger affected • increasing feed-down with increasing T QGP workshop, Erice, Sept 18, 2008

  29. More SPS and RHIC 200 GeV Data QGP workshop, Erice, Sept 18, 2008

  30. Model setting with gS • gS • sensitive on data sample • increase with size • increase with energy QGP workshop, Erice, Sept 18, 2008

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