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Event-by-event Particle Ratio Fluctuations in the CBM and NA49 experiments

Event-by-event Particle Ratio Fluctuations in the CBM and NA49 experiments. D. Kresan GSI, Darmstadt. CPOD 8 -th – 12 -th of June 2009 BNL, USA. Outline. Introduction Motivation NA49 data analysis Choosing bin size for centrality dependence Simulations with UrQMD

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Event-by-event Particle Ratio Fluctuations in the CBM and NA49 experiments

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  1. Event-by-event Particle Ratio Fluctuations in the CBM and NA49 experiments D. Kresan GSI, Darmstadt CPOD 8-th – 12-th of June 2009 BNL, USA

  2. Outline • Introduction • Motivation • NA49 data analysis • Choosing bin size for centrality dependence • Simulations with UrQMD • Centrality dependence of ratio fluctuations • Scaling of dynamical fluctuations • Simulations for CBM • Hadron identification • Effect of acceptance on dynamical fluctuations • Purity study • Conclusion D.Kresan CPOD Workshop, BNL

  3. Motivation arXiv: 0808.1237 [nucl-ex] Phys.Rev.D68:014507,2003 (hep-lat/0305007) D.Kresan CPOD Workshop, BNL

  4. NA49 is a fixed target experiment at CERN SPS Last data taking in 2002 Main PID detector – TPC No possibility for track-by-track identification Identification by TOF at midrapidity CBM is a future experiment at SIS300 (FAIR) Currently in design phase Hadron identification by TOF TOF resolution of better than 80 ps will provide possibility of track-by-track identification Introduction D.Kresan CPOD Workshop, BNL

  5. Choosing Centrality Bin Size Pb + Pb at 158A GeV Small difference between standard 3.5% and 5% centrality bin size Use bins of 5% for centrality dependence 20% 17.5% 5% 10% 15% 3.5% 3% D.Kresan CPOD Workshop, BNL

  6. Simulations with UrQMD (K/) Pb + Pb at 158A GeV by UrQMD v 1.3 UrQMD tracks were processed through the acceptance filter of NA49 For each UrQMD track a dE/dx value was simulated based on the PDFs from the fit of NA49 data Analyze NA49 data in centrality range from 0 to 35% With simulated dE/dx, UrQMD events were processed through the same analysis chain as data events Results for MC PID and e-b-e fit disagree for centralities lower than 35% D.Kresan CPOD Workshop, BNL

  7. Examples of K/ Ratio Distributions Pb + Pb at 158A GeV D.Kresan CPOD Workshop, BNL

  8. Centrality Dependence Pb + Pb at 158A GeV Absolute value of fluctuations decrease with increasing centrality Fluctuations decrease with increasing centrality K/ p/ Systematical errors are the difference between results for loose and tight track cuts D.Kresan CPOD Workshop, BNL

  9. Centrality Dependence of the K/p Fluctuations Pb + Pb at 158A GeV Absolute value of fluctuations decrease with increasing centrality D.Kresan CPOD Workshop, BNL

  10. Analytical formula fordyn ? D.Kresan CPOD Workshop, BNL

  11. Scaling of p/ Fluctuations  = 0.52 ± 0.06  = 0.66 ± 0.12 Centrality dependence at 158A GeV Energy dependence (central collisions) D.Kresan CPOD Workshop, BNL

  12. Scaling of K/ Fluctuations Different scaling for energy and centrality dependences D.Kresan CPOD Workshop, BNL

  13. Future CBM Experiment Investigation of A+A collisions from 10-45 AGeV beam energy: search for a first order phase transition and critical point in the intermediate, high net baryon density region of the QCD phase diagram Check sensitivity and layout with respect to particle ratio fluctuations and difficulties in method experienced in NA49 D.Kresan CPOD Workshop, BNL

  14. Hadron Identification identification track-by-track for e-b-e PID also works for low multiplicities and low K/ ratios Hadrons will be identified by TOF Good kaon-pion separation up to 3.5 GeV/c central Au + Au at 25 AGeV by UrQMD D.Kresan CPOD Workshop, BNL

  15. K/ Dynamical Fluctuations fromUrQMD RECO + PID 50% purity (p < 5 GeV/c) 4 No large acceptance bias D.Kresan CPOD Workshop, BNL

  16. Purity Study Fluctuations increase with increasing purity Purity restriction implies a momentum cut off for kaons In agreement with MC truth with momentum cut applied D.Kresan CPOD Workshop, BNL

  17. Conclusion • Analysis of Pb + Pb collisions at 158A GeV indicates that absolute value of dynamical fluctuations of particle ratios increase with decreasing centrality • Dynamical fluctuations of p/ follow scaling with number of identified particles – contribution of resonance decays • Energy dependence and centrality dependence of K/ fluctuations do not follow common scaling • Feasibility of measurement of event-by-event particle ratio fluctuations with future CBM experiment was shown • No strong bias from CBM acceptance, reconstruction and PID procedures is expected D.Kresan CPOD Workshop, BNL

  18. Backup slides D.Kresan CPOD Workshop, BNL

  19. p/ and K/p Fluctuations from UrQMD p/ K/p D.Kresan CPOD Workshop, BNL

  20. First Bin in K/ Distribution (UrQMD) D.Kresan CPOD Workshop, BNL

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