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Event-by-event Particle Ratio Fluctuations in NA49 and future CBM Experiment

Event-by-event Particle Ratio Fluctuations in NA49 and future CBM Experiment. D. Kresan for the NA49 and CBM Collaborations GSI, Darmstadt. DPG Spring Meeting 16-th – 20-th of March 2009 Bochum. Motivation. arXiv: 0808.1237 [nucl-ex]. Phys.Rev.D68:014507,2003 (hep-lat/0305007).

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Event-by-event Particle Ratio Fluctuations in NA49 and future CBM Experiment

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  1. Event-by-event Particle Ratio Fluctuations in NA49 and future CBM Experiment D. Kresan for the NA49 and CBM Collaborations GSI, Darmstadt DPG Spring Meeting 16-th – 20-th of March 2009 Bochum

  2. Motivation arXiv: 0808.1237 [nucl-ex] Phys.Rev.D68:014507,2003 (hep-lat/0305007) D. Kresan DPG Spring Meeting

  3. The NA49 Detector at CERN SPS momentum ranges: 20, 30, 40A GeV: 3 – 40 GeV/c 80, 158A GeV: 3 – 120 GeV/c Large acceptance hadron spectrometer , K, p PID detector: TPC (dE/dx measurement) D. Kresan DPG Spring Meeting

  4. Event-by-event Fit NO possibility for track-by-track PID Minimization of 2 for one event will fail due to low statistics Shape of the dE/dx distributions is obtained from the inclusive dE/dx fit Probability Density Functions (PDFs) Particle yields are determined by fitting the relative yields to the dE/dx spectrum using Maximum Likelihood Method D. Kresan DPG Spring Meeting

  5. Yield Ratio Distributions central Pb + Pb at 20A GeV Width of the distribution is dominated by the statistical fluctuations and dE/dx resolution Event mixing for the background estimation dyn2 = data2  mixed2 D. Kresan DPG Spring Meeting

  6. Energy dependence 3.5% most central As a first step, meant for validation of the software Increase towards lower SPS energies is confirmed by independent analysis arXiv: 0808.1237 [nucl-ex] Low sensitivity to the acceptance cuts D. Kresan DPG Spring Meeting

  7. Centrality Bin Size Dependence min-bias 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 DPG Spring Meeting

  8. Centrality Dependence min-bias Pb + Pb at 158A GeV Enhancement of first bin for peripheral events. Starts at centrality of about 30% due to low multiplicity D. Kresan DPG Spring Meeting

  9. Centrality dependence (2) min-bias Pb+Pb at 158A GeV Increase with decreasing centrality Follow 1/Npart scaling Resonance contribution? In case of K/ fluctuations saturation for peripheral events is observed K/ p/ Preliminary results! More understanding is needed D. Kresan DPG Spring Meeting

  10. Future CBM Experiment Intermediate energy regime  critical point? Check sensitivity and layout with respect to particle ratio fluctuations and difficulties in method experienced in NA49 D. Kresan DPG Spring Meeting

  11. 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 DPG Spring Meeting

  12. K/ Dynamical Fluctuations fromUrQMD RECO + PID 50% purity (p < 5 GeV/c) 4 No large acceptance bias D. Kresan DPG Spring Meeting

  13. 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 DPG Spring Meeting

  14. Conclusion • NA49 • energy and centrality dependence of particle ratio fluctuations was measured by NA49 • energy dependence is in agreement with independent analysis • fluctuations increase towards lower centralities • CBM • feasibility of the measurement of event-by-event particle ratio fluctuations shown • no strong bias from the acceptance, reconstruction and PID procedures is introduced D. Kresan DPG Spring Meeting

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