Simulations on the Event-by-event Fluctuations of the Particle Yield Ratios

1. Simulations on the Event-by-event Fluctuations of the Particle Yield Ratios D. Kresan, V. Friese GSI, Darmstadt, Germany Correlations and Fluctuations in Relativistic Nuclear Collisions Arcetri, Florence July 7-9 2006

2. Outline • Motivation • Definition of dynamical fluctuations • NA49 results vs. UrQMD – previous studies and consistency • UrQMD studies • single particle ratios (K+ over pi+/ and vice versa) • acceptance effects • resonance decay influence • hadronic cascades • Toy model simulations (K* and  decay) D. Kresan Correlations and Fluctuations Workshop, Florence

3. Motivation E-b-e fluctuations of the particle yield ratio are proposed as the signature for the critical endpoint But influence of acceptance, resonance decays and hadronic cascades on e-b-e fluctuations remains to be studied Model to start from – UrQMD. Has both resonances and re-scattering D. Kresan Correlations and Fluctuations Workshop, Florence

4. Dynamical Fluctuations Measure the particle yields ratio in an event : K/  = RMS / MEAN Relative width of distribution : data2 = fin2 + exp2 + dyn2 background mixed Event mixing: no two tracks coming from one real event dyn2 = data2  mixed2 D. Kresan Correlations and Fluctuations Workshop, Florence

5. NA 49 Measurements vs. UrQMD C.Roland @ QM 2004 D. Kresan Correlations and Fluctuations Workshop, Florence

6. Acceptance Effects – forward rapidity 4 y > ycm D. Kresan Correlations and Fluctuations Workshop, Florence

7. Acceptance Effects – momentum cut (PID) 4 • Possible reasons for differences: • Different UrQMD versions ? • Different acceptance conditions (acceptance filter vs. simplified cuts) y > ycm plab>3GeV/c D. Kresan Correlations and Fluctuations Workshop, Florence

8. UrQMD Results 4 central Au+Au at 25 AGeV real D. Kresan Correlations and Fluctuations Workshop, Florence

9. Acceptance Effects central Au+Au at 25 AGeV by UrQMD Acceptance effect is present but not dramatic D. Kresan Correlations and Fluctuations Workshop, Florence

10. Sources of Kaons in UrQMD 1.3 Results of collision history analysis central Au+Au at 25 AGeV by UrQMD Majority of kaons come from the K* decay D. Kresan Correlations and Fluctuations Workshop, Florence

11. K* Decay Suppressed central Au+Au at 25 AGeV by UrQMD real D. Kresan Correlations and Fluctuations Workshop, Florence

12. Summary Table D. Kresan Correlations and Fluctuations Workshop, Florence

13. Resonances in Toy Model – K* K*(892)0 K <K> = 41 <> = 363 Independently produced: • Toy Model features: • Independent particle production with yields and kinematics from UrQMD • Fluctuations of Kaon number of various amplitude • Resonance decays • Chains of resonance decays D. Kresan Correlations and Fluctuations Workshop, Florence

14. Resonances in Toy Model –  <K> = 41 <> = 363 Independently produced: K+K  K0LK0S 00 0 + analytical formula D. Kresan Correlations and Fluctuations Workshop, Florence

15. Conclusion • Our results of UrQMD simulations are consistent with ones obtained by C.Roland • Acceptance has effect on resulting fluctuations • K* decay is not the only source of correlations • Positive fluctuations of the (K++K)/(++) ratio in UrQMD are mainly due to  decay • Possibly charge conservation ??? • Interpretation of this observable is feasible ONLY IF yields (and phase space distr.) of all resonances and daughter particles are known D. Kresan Correlations and Fluctuations Workshop, Florence