Equation of State Study in UU collisions at CSR, Lanzhou

1. Equation of State Study in UU collisions at CSR, Lanzhou Z. G. Xiao Institute of Modern Physics, CAS, Lanzhou, China Quark Matter 2006 Nov14-20 Shanghai, China Collaborators: X. Dong2, F. Liu3, X.F. Luo2, K.J. Wu3, H. S. Xu1, N. Xu4 1 Institute of Modern Physics 2 University of Science and Technology of China 3 Central China Normal University 4 Lawrence Berkeley National Laboratory

2. Contents • 1 Introduction: EOS interest • 2 HIRFL-CSR* complex 2.1 Machine status 2.2 Experiment: status & plan • 3 UU collision simulations 3.1 High density in UU 3.2 Event selection • 4 Summary HIRFL: Heavy Ion Research Facility at Lanzhou CSR : Cool Storage Ring (500~1000MeV/u for HI )

3. GMR … M-R Max. M. Const. … … Flow K,… Cluster Compact Star: Initial conditions Transport Process Evolution dynamics Initial conditions Star fate, … Freeze Out Nucl. EOS H I C: EOS and its general interest • EOS used as input, tested by exp./model. consistency.

4. EOS representation  Esym T. Klaehn et al., Phys. Rev. C 74, 035802 (2006)

5. CSR Key Issues for EoS Program • 1 Identify the bulk-matter with partonic degrees of freedom • 2 Study the properties of the partonic matter • 3 Demonstrate the transition between partonic and hadronic worlds • 4 Understand multi-facets of HIC relevant to EOS study

6. 1 Introduction: EOS interest • 2 HIRFL-CSR* complex 2.1 Machine status 2.2 Experiment: status & plan • 3 UU collision simulations 3.1 High density in UU 3.2 Event selection • 4 Summary

7. ITE ETE J. W. Xia et al., NIMA 488, (2002) 11 HIRFL-CSRcomplex • ECR  Ion Source • SFC k=70 (few AMeV) • SSC k=450(~100 AMeV) • CSRm Cooler synch. ~12.6Tm ~2.8GeV proton • CSRe Acc./Deccel. ~9.6Tm • RIBLL2 R~1200 • Commission: 2006~2007

8. CSR Performance

9. 06/10/15 22:45 7→1000MeV/u (C6+) Ramping Test H = 2→1, frf = 0.45→1.63MHz, G = 11.3Tm Particles: 2x108

10. External Target Facility (I) • Neutron + LCP +  • First experiment shifted to 2007

11. Conceptual Layout of ETF (II) • 4 times larger acceptance of Dipole + Tracking inside; • Gamma ball made of CSI; • TOF (mRPC) covers forward region (30o). • Five years of construction after approved

12. Scintillator : <80 Calorimeter: <100 Real Test Simulation NW: Prototype test/simulation results

13. 1 Introduction: EOS interest • 2 HIRFL-CSR* complex 2.1 Machine status 2.2 Experiment: status & plan • 3 UU collision simulations 3.1 High density in UU 3.2 Event selection • 4 Summary

14. Tip-Tip Body-Body Advantageous UU collisions δ=0.23, A=238  Deformation  larger volume along z axis  Good for collision dynamics studies ? Experimental observation ? Event selection

15. High energy Low energy Density achieved in UU • UU > AuAu at both energies • 20AGeV: Tip-tip > Body-Body 520AMeV: Tip-tip ~ Body-Body B. A. Li et al., PRC61(2000), 021903

16. Tip-Tip Body-Body Idea of the event selections • At b=0 v2 = 0 v2 ≠ 0 - high density! - longer duration! - easier reach thermalization!

17. Event selection in UU • Body-Body collisions exhibit large anisotropy in azimuth.

18. Event selection in UU • Event selection: 1) neutron multiplicity cut suppress body-body events 2) Larger ratio of tip-tip collisions survives a additional v2 cut. 3) Random geometrical configuration to be simulated.

19. 5 Summary • EOS studies are drawing much attention and calling for more systematic studies. • HIRFL-CSR at Lanzhou, China can hope to add opportunities for nuclear EOS study in the high net-baryon density region. An External Target Facility (ETF) is in the preparing stage and detector R&D has started. • UU collisions provide a unique opportunity for creating a system with extended energy density and duration. The advantage is maintained only by effective identification of the geometrical configuration. Correlation between v2 and forward neutron multiplicity might practically help in the relevant energy region.

20. BACKUP SLIDES START HERE

21. BUU calculations Phase Space at 400MeV/u symmetrical collisions

22. CSR QCD Phase Diagram

23. EOS from HIC • DF favors softer EOS, while EF favors harder one; • K roughly constrained in (167, 380) P. Danielewicz et al., Science, 298(2002), 1592 • Puzzles found more in detailed investigation • More in A. Andronic et al., PRC67(2003), 034907; PLB612(2005), 173 • C. Fuchs et al., Phys. Rev. Lett 86, 1974 (2001)

24. CSR range Complication arises (1): Finite size effect • Due to nuclear transparency, density and/or pressure achieved in HIC is not so high as the full stopped scenario predicts.  reduce the sensitivity on EOS ?  virtually “soften” EOS ? W. Reisdorf et al., PRL92(2004), 232301

25. CSR range Esym and its density dependence Probes: • Mesons: pion ratio, Kaon ratio • n/p differential flow, ratio • n/p ratio of fast nucleons • Isospin diffusion • IMF isospin • HBT correlation function • ……

26. Esym: Isospin diffusion • 124Sn+112Sn Ein= 50MeV/u B. A. Li et al., PRC 72, 064611 (2005) L. W. Chen et al., PRL 94, 032701(2005) M. B. Tsang et al., PRL92, 062701(2005)

27. Why ??? Aladin+FOPI BUU model Y. Leifels et al., PRL71(1993),963 Esym: n/p flow • n/p flow predicted different, while experimentally NOT observed! Au+Au 400MeV/u B. A. Li, PRL88 (2001), 192701

29. Neutron Wall Main parameters

30. Big Dipole ready Main parameters MWDC before and after dipole