1. The Physics of Compressed Nuclear Matter at GSI and FAIR The 10th International Conference on Nucleus-Nucleus Collisions, August 16-21, 2009, Beijing, China Joachim Stroth, Goethe-University / GSI, Germany

2. Agenda o Motivation o Recent remarkable results from SIS18 o The persepective and challenge at FAIR o Summary  Not included in the talk – Bulk observables, Fluctuations, Flow

3. The phase diagram of nuclear matter Chemical freeze-out points derived from Statistical Hadronization Model  Universal conditions for freeze-out (?)  Limiting temperature T max ?  Why is it woking at low beam energies? QCD inspired models demonstrate the melting of the condesates. A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel J. Cleymans, K. Redlich LQCD explores unknown regions from solid grounds at  B =0.  T c = T max ?  1st order phase transition  Critical point ? Schäfer, Wambach priv. communication Schäfer, Wambach priv. communication Leupold J.Phys.G32:2199,2006 LHC RHIC SPS FAIR SIS AGS

4. Ignorant interpretation (Cloudy Bag Model) q q q q q q q q q q q q q q q q q q q q q q q q 1 fm : equiv. to 100 MeV (uncertainty relation)

5. T  T c, m B ~ 0 q q q q q q q q q q q q q q q q q q q q q q q q qq - - - - - - - - - Excitation/melting of the vacuum/cloud.  smooth cross over

6. T << T c, finite  B q q q q q q q q q q q q q q q q q q q q q q q q qq -

7. T << T c, finite  B q q q q q q q q q q q q q q q q q q q q q q q q Bag fusion  mixed phase

8. Phase diagram from large N c limit McLerran, Pisarski: QM09  conjecture for N c = 3 Quarkyonic Matter: Confined gas of perturbative quarks!

9. Strange Particle Production at SIS18 HADES, Ar+KCl at 1.76 GeV/u FOPI (P. Gasik CPOD 2009), Al+Al at 2 GeV/u T chem = 70  3 MeV  B = 746  15 MeV R C = 2.6  0.4 fm preliminary Statistical Model: THERMUS, S. Wheaton and J. Cleymans, hep-ph/0407174 Transport: UrQMD, M. Bleicher, S. Vogel at al. HADES collab.: arXiv:0907.3582 HADES collab.: arXiv:0907.3582 and arXiv:0902.3487arXiv:0902.3487

10. Properties of the Fireball at below E beam < 30 GeV/u Long lifetime of the high- density phase Baryon dominated Extented region of a strongly interacting hadron gas Red line from Hadron Gas Model, Sasaki QM09

11. Dileptons from 1 and 2 GeV/u 12 C+ 12 C runs Phys.Rev. Lett 98(2007) 052302 Phys. Lett. B 663 (2008) 43  Good normalization established in  0 region  Measured pair excess in C+C scales with beam energy as   production  What is the contribution from the initial phase? l+l+ l-l- ** ** l+l+ l-l- ** l+l+ l-l-

12. 12 Electron-pair spectrum decomposition Mesons (known) Baryon resonances Not measured but important at lower beam energies Two-body decays (known) :      e+ e-    e+ e-   e+ e- pp @3.5 GeV 00    //

13. The solution to the DLS puzzle C+C collisions compared to NN reference HADES data agrees with DLS

14. Electron pairs from Ar+KCl at 1.76 GeV/u First observation of  mesons in HI collisions at these energies x 2 PLUTO A Compared to reference after subtraction of contributions from  preliminary F ~ 3

15. The Future at GSI and FAIR SIS18 Several FOPI runs on strangeness production in 2008 – 2010 Upgraded HADES (20 KHz reaction rate) Au+Au and Ag+Ag, pion induced reactions from 2010 on. SIS100: Joint running of HADES and preCBM, multistrange particle and lepton pair excitation function, charm production in proton induced reactions SIS300: Full exploitation of rare probes a high  B; fluctuations, flow

16. Particle multiplicities in detection channel Au+Au at 25 GeV/u HSD transport calculation and statistical hadronization model. Not fully dressed in HI collisions at AGS and lower SPS energies

17. The Quest for the Highest Densities J. Randrup and J. Cleymans, hep-ph/0607065 Freeze-out configurations for X+X collisions in the net-baryon density and energy density plane.

18. Low-mass vector mesons. What do they tell about chiral symmtery restoration?

19. Low-mass lepton pairs, … the link to the microscopic properties of dense baryonic matter … the link to the microscopic properties of dense baryonic matter. Special role of the  meson: – short life time – „photon-like“ – coupling to baryons! isentropic expansion Thermal dilepton rates see e.g. R. Rapp, J. Wambach and H. Hees : arXiv:0901.3289, and S. Leupold, U. Mosel and V. Metag arXiv:0907.2388 R.Arnaldi,etal.[NA60collaboration], Phys.Rev.Lett.96,162302(2006 R.Arnaldi,etal.[NA60collaboration], Phys.Rev.Lett.96,162302(2006 )

20. New approaches in theory Hybrid codes for modeling the reaction dynamics 1.Non-equilibrium initial conditions via UrQMD 2.Hydrodynamic evolution or Transport calculation 3.Freeze-out via adronic cascade (UrQMD) hydro running time hydro start time Pb+Pb, central (Petersen et al., PRC 78:044901, 2008, arXiv: 0806.1695) Introduce virtual photon emissivity from in-medium spectral functions with hydro codes R. Rapp, H. van Hees, V. Toneev, J. Wambach, B. Friman, Texas A&M, TU Darmstadt, GSI, Giessen, Frankfurt

21. Ring Imaging Cherenkov Detector Transition Radiation Detectors Electron identification in CBM

22. Electron-pair reconstruction in CBM Challenge -No electron identification before tracking -Background due to material budget of the STS -Sufficient  discrimination (600   /event  misidentification 10 -4 ) Reduction of background by reconstructing pairs from  -conversion (~3  ) and   Dalitz decay (8   /event) e-e- e+e+  00   00  Track Segment Track Fragment

23. Background rejection performance Central Au+Au collisions at 25 GeV/u Free cocktail only (without medium contribution) Statistic: 200000 events = beam spill on target All e + e - Combinatorial bg Invariant mass spectrum after all cuts applied Invariant mass spectrum identified e + e -

24. M ll > 200 MeV/c 2 safety factor ;) NA60 In+In @ 158 AGeV CERES Pb+Au @ 40 AGeV CERES Pb+Au @ 158 AGeV (σ/σ tot = 28%) CERES Pb+Au @ 158 AGeV (σ/σ tot = 7%) CERES Pb+Au @ 158 AGeV PHENIX Au+Au @ √s = 200 AGeV Comparison of expected performance to existing dilepton experiments

25. Charmonium suppression. c c -

26. The Charm of CBM Rare but measurement feasible! – Very sparse experimental information – At threshold, production mechanism in pA and AA unclear. Open charm in CBM BRM / 10 12 events 1) 4 10 -5 56000 1 10 -4 174000 9 10 -5 195000 4 10 -5 103000 10 12 events  40 weeks running at 10 5 interaction rate.  Event selection: Real-time vertex finding in 20 Gbyte data/s. W. Cassing, E.L. Bratkovskaya, and A. Sibirtsev, Nucl.Phys.A691,753(2001)

27. Near threshold charm production < 20 MeV~ 780 MeV760 MeV97 % ~ 190 MeV1020 MeV830 MeV81 % ~ 2500 MeV3097 MeV597 MeV19 % Does charm at FAIR play the same role like Strangeness at GSI? Substantial differences due to the large charm quark masses: – Different interaction/production mechanism (Meson vs. Pomeron exchange) – Charm pair produced in very short instant of time (~ 1/m c, i.e. of order 0,1 fm) – Hadron formation time possibly similar (time needed to establish the proper sea- quark and gluon distribution)  Medium-effects may determine the charm distribution over hadronic degrees of freedeom but likely not the multiplicity!

28. Charm propagation How are the produced charm quarks propagating in the dense phase, quark like or (pre-)hadron like ? – Charmonium over open charm as indicator! – Charmed baryons important for a complete picture. – Are there indications of collectivity. O. Linnyk, E. Bratkovskaya and W. Cassing, arXiv:0808.1504v1 A. Andronic, P. Braun-Munzinger, et al., Phys. Lett. B 659 (2007) 149, arXiv:0708.1488

29. Summary – „Long-lived“ states of dense nuclear matter are produced in collisions of heavy ion at energies of a few GeV/u. – The phase in the high-density region might be much more exotic then a hadron/resonance gas. – Unfortunately, there is no smoking gun, but: Fast equillibration „Sub-threshold“ production Strong broadening of in-medium states – Close collaboration with, and novel approaches in theory are necessary to make the case.