Simulations on the Eventbyevent Fluctuations of the Particle
Simulations on the Event-by-event Fluctuations of the Particle Yield Ratios D. Kresan, V. Friese GSI, Darmstadt, Germany Correlations and Fluctuations July 7 2006 D. Kresan in Relativistic Nuclear Collisions Arcetri, Florence July 7 -9 2006 Correlations and Fluctuations Workshop,
Outline • Motivation • Definition of dynamical fluctuations • NA 49 results vs. Ur. QMD – previous studies and consistency • Ur. QMD studies – – single particle ratios (K+ over pi+/ and vice versa) acceptance effects resonance decay influence hadronic cascades • Toy model simulations (K* and decay) July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 2
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 – Ur. QMD. Has both resonances and re-scattering July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 3
Dynamical Fluctuations Measure the particle yields ratio in an event : Relative width of distribution : K/ = RMS / MEAN data 2 = fin 2 + exp 2 + dyn 2 background Event mixing: no two tracks coming from one real event July 7 2006 dyn 2 = data 2 mixed 2 D. Kresan mixed Correlations and Fluctuations Workshop, Florence 4
NA 49 Measurements vs. Ur. QMD C. Roland @ QM 2004 July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 5
Acceptance Effects – forward rapidity 4 y > ycm July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 6
Acceptance Effects – momentum cut (PID) 4 Possible reasons for differences: 1. Different Ur. QMD versions ? 2. Different acceptance conditions (acceptance filter vs. simplified cuts) y > ycm plab>3 Ge. V/c July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 7
Ur. QMD Results 4 central Au+Au at 25 AGe. V real July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 8
Acceptance Effects central Au+Au at 25 AGe. V by Ur. QMD dyn (%) 4 y > ycm K/ 2. 6 0. 2 2. 2 0. 6 y>ycm && plab>3 Ge. V/c 3. 4 0. 6 p/ -5. 51 0. 04 -6. 14 0. 08 -7. 0 0. 1 K+/ + -6. 2 0. 1 -7. 0 0. 3 -6. 1 0. 5 K+/ -7. 9 0. 1 -9. 0 0. 2 -8. 6 0. 3 K / + -8. 9 0. 3 -9. 3 0. 6 -10. 7 K / -7. 5 0. 3 -7. 2 0. 8 -6. 7 1. 2 Acceptance effect is present but not dramatic July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 9
Sources of Kaons in Ur. QMD 1. 3 Results of collision history analysis central Au+Au at 25 AGe. V by Ur. QMD Majority of kaons come from the K* decay July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 10
K* Decay Suppressed central Au+Au at 25 AGe. V by Ur. QMD real July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 11
Summary Table σdyn Nominal no K* decay no decay t = 5 fm/c t = 2 fm/c K/ 2. 6 0. 3 6. 7 0. 2 1. 3 0. 5 6. 4 0. 1 12. 0 0. 1 p/ -5. 52 0. 04 -5. 59 0. 04 -5. 51 0. 04 -5. 48 0. 04 -2. 68 0. 1 K+/ + -6. 2 0. 1 -3. 6 0. 6 -6. 3 0. 1 -3. 9 0. 2 -4. 2 0. 6 K+/ -8. 0 0. 1 -6. 3 0. 3 -8. 2 0. 1 -6. 3 0. 1 -8. 1 0. 3 K / + -8. 7 0. 3 -8. 1 0. 3 -8. 8 0. 3 -7. 3 0. 3 -7. 8 0. 6 K / -7. 0 0. 4 -6. 6 0. 4 -7. 3 0. 4 -5. 8 0. 3 -4. 7 0. 9 σdyn K* contribution t = 5 fm/c t = 2 fm/c K/ -6. 2 0. 3 2. 3 0. 5 -5. 8 0. 2 11. 7 0. 1 p/ 0. 9 0. 4 -0. 3 0. 9 -0. 7 0. 5 -4. 83 0. 07 K+/ + -5. 0 0. 4 1. 1 0. 8 -4. 8 0. 2 -4. 6 0. 6 K+/ -4. 9 0. 4 1. 8 0. 6 -4. 9 0. 2 1 2 K / + -3. 2 1. 1 1. 3 2. 8 -4. 7 0. 7 3. 9 1. 4 K / -2. 3 1. 6 2. 1 2. 0 -3. 9 0. 8 5 1 July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 12
Resonances in Toy Model – K* K*(892)0 K Independently produced: <K> = 41 < > = 363 Toy Model features: 1. Independent particle production with yields and kinematics from Ur. QMD 2. Fluctuations of Kaon number of various amplitude 3. Resonance decays 4. Chains of resonance decays July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 13
Resonances in Toy Model – <K> = 41 < > = 363 Independently produced: K +K K 0 LK 0 S 0 0 0 + July 7 2006 D. Kresan analytical formula Correlations and Fluctuations Workshop, Florence 14
Conclusion • Our results of Ur. QMD 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 Ur. QMD 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 July 7 2006 D. Kresan Correlations and Fluctuations Workshop, Florence 15
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