Gary Westfall Michigan State University, USA

1. Experimental Results for Fluctuations And Correlations as a Signature of QCD Phase Transitions in Heavy Ion Collisions Gary Westfall Michigan State University, USA Gary Westfall, Quark Matter 2008

2. Correlations and Fluctuations • Depend on previous talk for theoretical justification • Search for discontinuities or changes in experimental results for correlations and fluctuations as a function of incident energy • K/π Fluctuations • Balance Function • Net Charge Fluctuations • Multiplicity Fluctuations • pt Correlations • RHIC Energy Scan • SPS Program 2 Gary Westfall, Quark Matter 2008

3. Plan • Present a sample of current experimental results • Not a complete survey • Will refer you to other talks at QM2008 • Make suggestions for measurements that could be done as a function of incident energy • Outline current plans for SPS and RHIC to study the incident energies of interest to the QCD critical point Gary Westfall, Quark Matter 2008

4. See talk by M. Rybczynski, Session X K/π Fluctuations NA49 Preliminary See talk by Z. Ahammed in Session X Gary Westfall, Quark Matter 2008

5. K/π Fluctuations Torrieri QM06 See talk by Z. Ahammed in Session X Gary Westfall, Quark Matter 2008

6. K/π FluctuationsScaling with dN/dη Au+Au statistical errors Cu+Cu statistical+systematic errors See talk by Z. Ahammed in Session X Gary Westfall, Quark Matter 2008

7. Balance Function • Charge fluctuations can be studied with several different variables that can be expressed in terms of each other • We choose to illustrate charge fluctuations using the balance function Bass, Danielewicz, Pratt PRL 85 2689 (2000) Gary Westfall, Quark Matter 2008

8. Balance Function NA49 Phys. Rev. C 76, 024914 2007 Balance functions for Pb+Pb at sNN½ = 6.3 to 17.3 GeV Data Shuffled STAR, QM 02, QM 04 Balance functions for Au+Au at sNN½ = 20 to 200 GeV Au+Au 200 GeV Gary Westfall, Quark Matter 2008

9. Balance Function NA49 Phys. Rev. C 76, 024914 2007 NA49 Large W means narrow balance function Gary Westfall, Quark Matter 2008

10. Net Charge Fluctuations at RHIC See poster by M. Sharma Gary Westfall, Quark Matter 2008

11. Net Charge Fluctuations at RHIC The slope in p+p, Cu+Cu and Au+Au depends on the correlation length: the shorter the correlation, the larger the slope The distributions indicate that the correlation length is shorter for central collisions and for larger systems, in agreement with the observed reduction of the width of the balance function See poster by M. Sharma 11 Gary Westfall, Quark Matter 2008

12. Net Charge Fluctuations at the SPS NA49 PRC 70, 064903 (2004) Gary Westfall, Quark Matter 2008

13. Multiplicity Fluctuations NA49, 0712.321 [nucl-ex] 2007 1% most central Scaled to 4π Gary Westfall, Quark Matter 2008

14. pt Fluctuations Adamova et al., CERES Miskowiec for NA49, CPOD 2007 Gary Westfall, Quark Matter 2008

15. pt Fluctuations Calculate <Δpt,i,Δpt,j> for pairs within a given range of Δϕ and multiply by dN/dη The region of 30° < Δϕ < 60° is free from effect such as HBT and jets and may be a fruitful region to search for discontinuities as a function of incident energy Adamova et al., CERES Gary Westfall, Quark Matter 2008

16. Forward/Backward Multiplicity Correlations See talk by B. Srivistava Session XIX See poster 176 by T. Tarnowsky Gary Westfall, Quark Matter 2008

17. Energy Dependence of F/B Multiplicity Fluctuations Central Au+Au 0 – 10% Long range correlations are an indicator of multiple elementary elastic collisions 200 GeV 62.4 GeV Long range correlations decreases as the incident energy is decreased STAR preliminary See talk by B. Srivistava Session XIX See poster 176 by T. Tarnowsky Gary Westfall, Quark Matter 2008

18. NA 49/61 Future Program M. Gazdzicki Gary Westfall, Quark Matter 2008

19. Proposed Energy and Mass Scans Gary Westfall, Quark Matter 2008

20. Addition of TOF to STAR • STAR will add TOF for Run 10 • The TOF will provide excellent particle identification for π, K, and p for a large fraction of the measured particles event-by-event • Improved K/π fluctuation measurements • Improved balance functions with identified π, K, and p • See talk by G. Odyniec, session XXIV P. Sorensen Charged pions and kaons 0.2 < pt < 0.6 GeV/c Gary Westfall, Quark Matter 2008

21. Balance Function with Identified Pions • The excellent particle identification for π, K, and p for a large fraction of the measured particles event-by-event will allow new kinds of event-by-event measurements such as the balance function with identified particles Charged pion pairs 0.2 < pt < 0.6 GeV/c Gary Westfall, Quark Matter 2008

22. Conclusions 1 • We have experimental results for correlations and fluctuations covering incident energies where one might expect effects from the QCD critical point and we have some hints in the • However, the results are not conclusive • In particular, we have several different variables, acceptances, and interpretations that need to be unified • We need to measure correlation fluctuation variables over the broadest range in incident energy and system size Gary Westfall, Quark Matter 2008

23. Conclusions 2 • The SPS and RHIC scans will provide an excellent opportunity to study the QCD critical point • SPS system/energy scan will add a large number of points in T/μB space in the search for the critical point • We also look forward to correlations and fluctuations related to the QCD phase transition at GSI/FAIR Gary Westfall, Quark Matter 2008

24. Extra Slides Gary Westfall, Quark Matter 2008

25. Relation between Net Charge Fluctuations and the Balance Function Jeon and Pratt PRC 65, 044902 (2002) Gary Westfall, Quark Matter 2008

26. HBT Gary Westfall, Quark Matter 2008

27. HBT Gary Westfall, Quark Matter 2008