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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 TU Darmstadt. Outline. Predictions for Pb+Pb Extrapolation of thermal parameters, predictions Experimental observables for T and μ B determination From Pb+Pb to p+p: Model ansatz with correlated clusters

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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 TU Darmstadt

  2. Outline • Predictions for Pb+Pb • Extrapolation of thermal parameters, predictions • Experimental observables for T and μB determination • From Pb+Pb to p+p: Model ansatz with correlated clusters • Predictions for p+p • Driven by initial or final state? • Summary • in Collaboration with H. Oeschler, K. Redlich, J. Cleymans, S. Wheaton SQM 2006, UCLA, March 26, 2006

  3. Comparison to Experimental Data A.Andonic, P. Braun-Munzinger, J. Stachel, nucl-th/0511071 • Different data selected for fits • Accurancy in T, mB: few MeV SQM 2006, UCLA, March 26, 2006

  4. Thermal Parameters in Pb+Pb 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 Nucl. Phys. A 697 (2002) 902 Grand canonical ensemble for Pb+Pb predictions hep-ph/0511094 SQM 2006, UCLA, March 26, 2006

  5. Predictions for Pb+Pb • Reliable for stable particles • Benchmark for resonances • Errors: T = 170 +/- 5 MeV μB = 1 + 4 MeV - 1 All calculations with THERMUS hep-ph/0407174 SQM 2006, UCLA, March 26, 2006

  6. Analytical check • Off by factor 2! • Particle yield = thermal production + feed-down contributions SQM 2006, UCLA, March 26, 2006

  7. 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 _ _ SQM 2006, UCLA, March 26, 2006

  8. _ T and μB dependence I: h/h ratios • Sensitive on μB • μS opposite trend of μB • determine μB from p/p • weakly dep. on T ☺ _ SQM 2006, UCLA, March 26, 2006

  9. T and μB dependence II: 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 SQM 2006, UCLA, March 26, 2006

  10. T dependence: ratios with large mass differences • Ratios with larger mass differences are more sensitive T from W / p and/or W / K ☺ SQM 2006, UCLA, March 26, 2006

  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 R RC SQM 2006, UCLA, March 26, 2006

  12. System size and energy dependence of T and mB • T independent of • System size • Data selection • Energy • μB smaller at RHIC SQM 2006, UCLA, March 26, 2006

  13. System size and energy dependence of the cluster size • p+p • energy dependence? • Pb+Pb • depends on data selection (multi-strange hadrons needed) SQM 2006, UCLA, March 26, 2006

  14. 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 SQM 2006, UCLA, March 26, 2006

  15. Canonical Suppression • Particle ratios saturate at RC ≈ 2 - 3 fm • no precise determination for small strangeness suppression SQM 2006, UCLA, March 26, 2006

  16. Extrapolation to LHC • 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 SQM 2006, UCLA, March 26, 2006

  17. 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 SQM 2006, UCLA, March 26, 2006

  18. 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 _ SQM 2006, UCLA, March 26, 2006

  19. _ Resonance Contribution to p/p • Ratio not affected by feeding • net baryon number is conserved SQM 2006, UCLA, March 26, 2006

  20. Resonance Contribution to K and p SQM 2006, UCLA, March 26, 2006

  21. 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 SQM 2006, UCLA, March 26, 2006

  22. Data Set • Selection: p+ / p- K+ / K- L / L K- / p- L/ K+L / K-p- same for p+p C+C Si+Si Pb+Pb 4p and C+C Si+Si Pb+Pb mid rapidity @ 158 A GeV • Compare different model settings • Equilibrium: parameters T, μB, R • Fit gS : parameters gS, T, μB, R • Fit RC: parameters RC, T, μB, R SQM 2006, UCLA, March 26, 2006

  23. Fit Example • All Fits were performed with THERMUS hep-ph/0407174 • Fits with gS / RC give better description of data SQM 2006, UCLA, March 26, 2006

  24. System size dependence of T and mB • μB decreases at mid-rapidity in small systems …. • …. as expected from increasing antibaryon / baryon ratio SQM 2006, UCLA, March 26, 2006

  25. System size dependence of the cluster size Same trend as K / p SQM 2006, UCLA, March 26, 2006

  26. More SPS and RHIC 200 GeV Data SQM 2006, UCLA, March 26, 2006

  27. Model setting with gS • gS • sensitive on data sample • increase with size • increase with energy SQM 2006, UCLA, March 26, 2006

  28. Prediction for p+p • similar trend is seen in gS dependence SQM 2006, UCLA, March 26, 2006

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