1. Equation of State Study in UU collisions at CSR, Lanzhou Quark Matter 2006 Nov14-20 Shanghai, China Z. G. Xiao Institute of Modern Physics, CAS, Lanzhou, China Collaborators: X. Dong 2, F. Liu 3, X.F. Luo 2, K.J. Wu 3, H. S. Xu 1, N. Xu 4 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. EOS and its general interest EOS used as input, tested by exp./model. consistency. Nucl. EOS Initial conditions Star fate, … M-R Max. M. Const. … Evolution dynamics Compact Star: Initial conditions Freeze Out Flow K, … Cluster GMR … Transport Process H I C:

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

5. 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 CSR

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. HIRFL-CSR complex 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 ITE ETE J. W. Xia et al., NIM A 488, (2002) 11 Commission: 2006~2007

8. CSR Performance CSRmCSRe Ion speciesproton, C-Up, C-U,RIB,HCI Beam Energy (MeV/u) B max =1.6T 2.8GeV p 1.1GeV/u 12 C 6+ 0.52GeV/u 238 U 72+ 2.3GeV p ~1 GeV/u 12 C 6+ ~ 0.5 GeV/u 238 U 72+  P/P <10 － 4 <10 － 5  P/P  0.15%  0.5% Emittance  5  mm mrad  1  mm mrad

9. 7→1000MeV/u (C 6+ ) Ramping Test 06/10/15 22:45 H = 2→1, f rf = 0.45→1.63MHz, G = 11.3Tm Particles: 2x10 8

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 (30 o ). Five years of construction after approved

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

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

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

16. Idea of the event selections At b=0 Tip-Tip Body-Body v 2 = 0 v 2 ≠ 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 v 2 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 v 2 and forward neutron multiplicity might practically help in the relevant energy region.

20. BACKUP SLIDES START HERE

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

22. QCD Phase Diagram CSR

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 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. 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 CSR range

25. 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 …… CSR range

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

29. Neutron Wall Active area1.5×1.5m 2 Thickness1m Acceptance±3.8 0 coverage11~20 mSr Angular resolution0.3 0 Efficiency （ 1 GeV n ） >90% Position resolution±8cm E resolution （ < 1 GeV n ）  5 % Main parameters

30. Big Dipole ready Main parameters B Field1.6 Tesla Gap height270 mm Gap Width1000 mm Thickness980 mm Distance to target1 m MWDC before and after dipole