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

Heavy Ion Collisions School, Erice, Sept 18, 2008 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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Hadron ratios in the grand canonical ensemble large systems, large number of produced hadrons two parameters describe particle ratios in the hadronic final state T, V, m T, Vb, Nb A. Andronic, P. Braun-Munzinger, J. Stachel, Nucl. Phys. A772 (2006) 167 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Heavy Ion Collisions School, Erice, Sept 18, 2008 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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

T and μB dependence I: h / h ratios _ T and μB dependence I: h / h ratios Sensitive on μB determine μB from p/p weakly dep. on T ☺ _ Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

T dependence: ratios with large Dm Ratios with larger mass differences are more sensitive T from W / p and/or W / K ☺ Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

System size and energy dep. of cluster size RC= R Pb+Pb Au+Au A+A: clusters smaller than fireball RC not well defined for RC ≥ 2 fm because suppression vanishes Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Extrapolation to LHC: T - mB – systematics 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 Phys. Rev. C 73(2006) 034905 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

System size and energy dep. of T and mB T, μB weakly dependent on system size p+p C+C Si+Si Pb/Au Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

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 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Heavy Ion Collisions School, Erice, Sept 18, 2008 Prediction for p+p significant increase of ratios at RC ≈ 1.5 fm RC will be determined with ALICE data Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Heavy Ion Collisions School, Erice, Sept 18, 2008 Extraction of RC Sensitivity increases with strangeness difference RC from W / p ☺ hep-ph 0808.0611 Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Heavy Ion Collisions School, Erice, Sept 18, 2008 W / p For Pb+Pb ratio was proposed as a measure of T but … Sensitivity on canonical suppression is much stronger than on T Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Heavy Ion Collisions School, Erice, Sept 18, 2008 Summary Pb+Pb predictions for particle ratios with extrapolated parameters T, μB T, μB determination with p / p and W / K or W / p ratios p+p predictions difficult due to unknown degree of canonical suppression Cluster radius RC from data _ Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008

Heavy Ion Collisions School, Erice, Sept 18, 2008 Data and fits Ingrid Kraus, Nikhef Heavy Ion Collisions School, Erice, Sept 18, 2008