1. Laboratory for Nuclear Physics Division of Experimental Physics Ruđer Bošković Institute, Zagreb, Croatia Zoran Basrak 11th International Conference on Nucleus-Nucleus Collisions May 28 – June 1st, 2011, San Antonio, TX–USA Philippe Eudes, Maja Zorić, and François Sébille In collaboration with

2. Landau-Vlasov simulation Transport equation of the Boltzmann type H = T+U, U = V nucl +V Coul, V nucl – Gogny G1-D1 non-local potential K=228 MeV, m*/m=0.67 f = f(r,p;t) - distribution function Collision term Phenomenological, isotropic σ = σ(E, iso) [Chen et al.] An approach adequate for bulk (one-body) properties of nuclear dynamics, in particular for an early and compact reaction phase

3. Dynamical emission component P. Eudes, Z. Basrak and F. Sebille, Phys. Rev. C56 (1997) 2003. Landau-Vlasov model simulation Ar ( 65 MeV / u ) Al A similar two-stages process in 1A GeV range by EOS Coll J.A. Hauger et al. PRL 77 (1996) 235. A similar conclusion valid for any reaction below 100A MeV

4. Early reaction phase

5. Early energy transformation E tot = E collect + E intrin E intrin = E excit + E potent Decompression followed by abundant emission and fast system cooling. A sys = ~60 - ~400 nucl A proj :A targ = 1:1 – 1:5 SystemIncident energy (MeV/u) 40 Ar+ 27 Al25, 41, 53, 65, 77, 99 36 Ar+ 58 Ni52, 74, 95 40 Ar+ 107 Ag20, 30, 40, 45, 50, 75, 100 40 Ar+ 197 Au50, 75, 100 36 Ar+ 36 Ar32, 40, 52, 74 58 Ni+ 58 Ni52, 74, 90 12O Xe+ 129 Sn25, 32, 39, 45, 50, 75, 100 197 Au+ 197 Au20, 30, 40, 60, 80, 100

6. Evolution of excitation energy – Regular rise & fall with time at each E IN – Width & height regularly behave as a f(E IN )

7. Evolution of excitation energy – Regular rise & fall with time at each E IN – Width & height regularly behave as a f(E IN ) – Maxima reflect the total energy deposited in the reaction system

8. Excitation energy maxima E proj A proj E avail = A targ A proj (A targ +A proj ) 2

9. E x as a fraction of E AVAIL – Fraction is almost constant over a wide energy range – Large variety of systems

10. Experimental excitation energy

11. All available data on E x /A in central HI collisions in the last 20 years Experimental excitation energy

12. All available data on E x /A in central HI collisions in the last 20 years – Strong spread of the data points – Connected data points of the same measurement – Close to linear dependence on E IN

13. Data for E IN > 100A MeV W. Reisdorf et al., Nucl. Phys. A848 (2010) 366. – Radial flow of light reaction products deduced on two manners – Some correction relative to FOPI PHASE 1 but still a linear function of E IN Radial flow deduced by blast model. Remaining energy is taken as thermal. W. Reisdorf et al., Nucl. Phys. A612 (1997) 493.

14. All available data on E x /A in central HI collisions in the last 20 years – Strong spread of the data points – Connected data points of the same measurement – Close to linear dependence on E IN Experimental excitation energy

15. All available data on E x /A in central HI collisions in the last 20 years – Strong spread of the data points – Connected data points of the same measurement – Close to linear dependence on E IN – Data within 35 % and 95 % of E AVAIL

16. E x as a fraction of E AVAIL – The same system for the central collisions and the same E IN displays different features

17. – The same system for the central collisions and the same E IN displays different features – Different leading assumption used in various analysis E x as a fraction of E AVAIL

18. D. Dore et al. (INDRA Collaboration), Phys. Lett. B491 (2000) 15. Ar (95A MeV) + Ni INDRA experiment analyzed in the 3 sources assumption QP emission in BDCs QP mass QP excitation experiment 3 sources analyses Proton reduced rapidity distribution Reaction dominantly of binary nature with a strong mid-rapidity contribution.

19. – The same system for the central collisions and the same E IN displays different features – Different leading assumption used in various analysis – Group data by the approach used E x as a fraction of E AVAIL

20. Neglected dynamical emission (?)

21. Pure kinematical considerations

22. Accounted dynamical emission

23. Added FOPI thermal energy

24. Summary

25. Laboratory for Nuclear Physics Division of Experimental Physics Ruđer Bošković Institute, Zagreb, Croatia Zoran Basrak 11th International Conference on Nucleus-Nucleus Collisions May 28 – June 1st, 2011, San Antonio, TX–USA Philippe Eudes, Maja Zorić, and François Sébille In collaboration with

26. Backup slides

27. Central collisions 30 fm/c = 1∙10 -21 s E x ≈E AVAIL full stopping E in = 10A MeV At E Fermi (≈ 35A MeV) “hard” NN collisions E in = 35A MeV 129 Xe + 120 Sn  BDC > 95 %  REAC ≈ 5 % σ REAC b = 3 fm ≈ 0.2 b max E in = 50A MeV E in = 125A MeV

28. Mid-rapidity emission in BDCs ≈ pre-scission emissionMid-rapidity emission max. compression local equilibration Configuration space Impulse space pre-scissionpost-scission P. Eudes, Z. Basrak and F. Sebille, Phys. Rev. C56 (1997) 2003.

29. Central collisions  Above Coulomb barrier an adiabatic system rearrangement with full stopping and full E dissipation; fusion process E DISSIP = E AVAIL  Increasing E: incomplete fusion E DISSIP < E AVAIL  From about the Fermi energy E Fermi BDC  BDC > 95 %  REAC irrespectively of - event centrality - system size - system asymmetry Increasing contribution of hard NN collisions

30. F. Haddad et al., Phys. Rev. C60 (1999) 031603. Z dynam emiss Z targ + Z proj = 100 Dynamical emission component D em (%) = System Incident energy (MeV/u) 40 Ar+ 27 Al41, 65 40 Ar+ 107 Ag50, 75, 100 107 Ag+ 40 Ar50 36 Ar+ 58 Ni52, 74, 95 12O Xe+ 129 Sn50, 75, 100

31. Excitation energy maxima E proj A proj E avail = A targ A proj (A targ +A proj ) 2

32. E x as a fraction of E AVAIL – Fraction almost constant over a wide energy range – For symmetric systems break below E Fermi – Large variety of systems

33. Fraction for experimental E x

34. Binary Dissipative Collisions (BDC) – BDC opens around the Fermi energy – σ BDC > 95% σ REAC Irrespectively of - event centrality - system size - system mass asymmetry V.Metivier et al. (INDRA Collaboration), Nucl. Phys. A672 (2000) 357.

35. QP emission in BDCs J. Peter et al., Nucl. Phys. A593 (1995) 95.  Reconstructed primary QP mass approxim.. equal to the projectile mass  Thus obtained primary QP extremely hot Y.-G. Ma et al., Phys. Lett. B390 (1997) 41. Ar (95 MeV/u) Ni

36. Statistical emission component Ph. Eudes and Z. Basrak, Eur. Phys. J. A 9 (2000) 207. Landau-Vlasov model simulation Ar ( 65 MeV / u ) Al The geniune primary QP emission Ar (65 MeV/u) Al D. Cussol et al., Nucl. Phys. A561 (1993) 298. J. Peter et al., Nucl. Phys. A593 (1995) 95.

38. Heat & compression – Maximal compression at ~25 fm/c – In each volume cell a local equilibration at ~35 fm/c – System scission at ~55 fm/c Despite of the establishment of a local equi- librium throughout the compact system the (E th /A) sys and (A th /A) proj differ substantially: Global equilibrium is far from being reached I. Novosel et al., Phys. Lett. B625 (2005) 26.

39. Head-on collisions A universal linear proportionality law proves the eminent role of “hard” NN collisions. A targ (A targ + A proj ) 2 E avail = c.m. E proj A proj Dependence on available energy I. Novosel et al., Phys. Lett. B625 (2005) 26.

40. Dependence of relative sub-systems E th /A on incident energy for head-on collisions I. Novosel et al., Phys. Lett. B625 (2005) 26. Projectile ratio = (E th /A) proj Target ratio = (E th /A) sys (E th /A) tar g (E th /A) sys Ratio of thermal energy maxima

41. Dependence of relative sub-systems E th /A on incident energy for head-on collisions I. Novosel et al., Phys. Lett. B625 (2005) 26. Projectile ratio = (E th /A) proj Target ratio = (E th /A) sys (E th /A) tar g (E th /A) sys A symmetric system Ratio of thermal energy maxima

42. Dependence of relative sub-systems E th /A on incident energy for head-on collisions I. Novosel et al., Phys. Lett. B625 (2005) 26. Projectile ratio = (E th /A) proj Target ratio = (E th /A) sys (E th /A) tar g (E th /A) sys An asymmetric system Ratio of thermal energy maxima

43. Dependence of relative sub-systems E th /A on incident energy for head-on collisions I. Novosel et al., Phys. Lett. B625 (2005) 26. Projectile ratio = (E th /A) proj Target ratio = (E th /A) sys (E th /A) tar g (E th /A) sys Increasingly asymmetric systems Ratio of thermal energy maxima

44. Dependence of relative sub-systems E th /A on incident energy for head-on collisions I. Novosel et al., Phys. Lett. B625 (2005) 26. Projectile ratio = (E th /A) proj Target ratio = (E th /A) sys (E th /A) tar g (E th /A) sys Ratio of thermal energy maxima

45. Dependence of relative sub-systems E th /A on incident energy for head-on collisions I. Novosel et al., Phys. Lett. B625 (2005) 26. tal change from the fusion-deep inelastic into the BDC – partic.-spect,(fireball)-like behavior.  The reaction geo- metry is important in intermediate E HIC.  The Fermi energy is a transient region where the main reac- tion mechanism un- dergoes a fundamen- Ratio of thermal energy maxima