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Heavy-ion dynamics at the Fermi energy A theoretical point of view

Heavy-ion dynamics at the Fermi energy A theoretical point of view. R uđer Bošković Institute – SUBATECH collaboration. Z oran Basrak. Laboratory for heavy-ion physics Division of Experimental Physics R uđer Bošković Institute, Zagreb, Croatia. EWON Town Meeting ,

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Heavy-ion dynamics at the Fermi energy A theoretical point of view

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  1. Heavy-ion dynamics at the Fermi energy A theoretical point of view RuđerBošković Institute – SUBATECH collaboration Zoran Basrak Laboratory for heavy-ion physics Division of Experimental Physics RuđerBošković Institute, Zagreb, Croatia EWON Town Meeting, May 10 –12, 2007, Prague, Czek Republic

  2. Talk overview • Introduction • The Fermi energy & BDC • QP properties • Mid-rapidity emission • Early energy transformation • Conclusions • Outlook

  3. From Coul. barrier to ~20 MeV/u Global properties • Mean fieldgovernscollision dynamics • The Pauli blocking “freezes”“hard” .NNcollisions Central collisions: Fusion Peripheral collisions: Binary Processes sTOT= sFUS+ s B.P.

  4. The Fermi energy region Expected global properties • Weakened influence of the mean field • With increasing energy larger phase . space opens to the NNcollisions sTOT= sFUS+ s B.P. Still holds: sTOT~ sFUS Till early 90’s believed: Hot nuclei !!!

  5. Binary Dissipative Collisions – BDC opens around the Fermi energy Irrespectively of - event centrality - system size - system asymmetry V.Metivier et al. (INDRA Collaboration), Nucl. Phys. A672 (2000) 357. sTOT< 0.05 sFUS

  6. BDC reaction mechanism A two-stage process: • A compact quickly evolving early .reaction phase (prior to scission) • By birth of the primary QP & QT .starts the second reaction phase

  7. QP emission in BDC’s • Reconstructed primary QP massapproxim.. equal to the projectile mass J. Peter et al., Nucl. Phys.A593 (1995) 95.

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

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

  10. Ar ( 65 MeV / u ) Al Dynamical emission component Landau-Vlasov model simulation Ph. Eudes, Z. Basrak and F. Sebille, Phys. Rev. C56 (1997) 2003.

  11. Ar ( 65 MeV / u ) Al Ar ( 65 MeV / u ) Al Dynamical emission component Landau-Vlasov model simulation Ph. Eudes, Z. Basrak and F. Sebille, Phys. Rev. C56 (1997) 2003.

  12. Ar ( 65 MeV / u ) Al Ar ( 65 MeV / u ) Al Dynamical emission component Landau-Vlasov model simulation Ph. Eudes, Z. Basrak and F. Sebille, Phys. Rev. C56 (1997) 2003.

  13. Z dynam emiss = 100 Z targ + Z proj Dynamical emission component Dem (%) = F. Haddad et al., Phys. Rev. C60 (1999) 031603.

  14. Ar ( 65 MeV / u ) Al Statistical emission component Landau-Vlasov model simulation Thegeniune primary QP emission

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

  16. QP emission in BDC’s Ar (95 MeV/u) + Ni INDRA experiment analyzed in the 3 sources assumption Proton reduced rapidity distribution experiment 3 sources analyses D. Dore et al. (INDRA Collaboration), Phys. Lett. B491 (2000) 15.

  17. Mid-rapidity emission in BDC’s pre-scission post-scission max. compression Configuration space local equilibration max. compression Impulse space local equilibration

  18. Mid-rapidityemission • pre-scissionemission Mid-rapidity emission in BDC’s pre-scission post-scission max. compression Configuration space local equilibration max. compression Impulse space local equilibration

  19. Etot = Ecollect + Eintrin Eintrin = Eexcit + Epotent Early energy transformation Decompression followed by abundant emission and fast system cooling.

  20. Eexcit Eth /A Etot = Ecollect + Eintrin Epotent Ecompr /A Eintrin = Eexcit + Epotent Early energy transformation I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. - Asys = ~70 - ~250 nucl - Aproj:Atarg = 1:1 – 1:5 - brel = 0, … (0.1) … 1 Decompression followed by abundant emission and fast system cooling.

  21. 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 I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26.

  22. 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 I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26.

  23. 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 I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. Despite of the establishment of a local equili-brium throughout the compact system the (Eth/A)sys and (Ath/A)proj differ substantially: Global equilibrium is far from being reached!

  24. Reaction geometry Maxima of the Eth/A and Acompr/A show as a function of reaction centrality strong geometrical effects. I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26.

  25. Reaction geometry Maxima of the Eth/A and Acompr/A show as a function of reaction centrality strong geometrical effects. I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. Observed feature is in the spirit of the participant-spectator picture.

  26. Reaction geometry Maxima of the Eth/A and Acompr/A show as a function of reaction centrality strong geometrical effects. I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. Observed feature is in the spirit of the participant-spectator picture. An interplay of the NN collisions and the Pauli principle in the overlap zone.

  27. c.m. E proj A targ A proj Eavail = A proj (A targ + A proj ) 2 Head-on collisions Dependence on available energy I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26.

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

  29. Ratio of thermal energy maxima Dependence of relative sub-systems Eth/A on incident energy for head-on collisions Projectile ratio = (Eth/A)proj (Eth/A)sys Target ratio = I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. (Eth/A)targ (Eth/A)sys

  30. Ratio of thermal energy maxima Dependence of relative sub-systems Eth/A on incident energy for head-on collisions Projectile ratio = (Eth/A)proj (Eth/A)sys Target ratio = I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. (Eth/A)targ (Eth/A)sys A symmetric system

  31. Ratio of thermal energy maxima Dependence of relative sub-systems Eth/A on incident energy for head-on collisions Projectile ratio = (Eth/A)proj (Eth/A)sys Target ratio = I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. (Eth/A)targ (Eth/A)sys An asymmetric system

  32. Ratio of thermal energy maxima Dependence of relative sub-systems Eth/A on incident energy for head-on collisions Projectile ratio = (Eth/A)proj (Eth/A)sys Target ratio = I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. (Eth/A)targ (Eth/A)sys Increasingly asymmetric systems

  33. Ratio of thermal energy maxima Dependence of relative sub-systems Eth/A on incident energy for head-on collisions Projectile ratio = (Eth/A)proj (Eth/A)sys Target ratio = I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. (Eth/A)targ (Eth/A)sys Increasingly asymmetric systems

  34. Ratio of thermal energy maxima Dependence of relative sub-systems Eth/A on incident energy for head-on collisions • 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- I. Novosel, Z. Basrak et al., Phys. Lett. B625 (2005) 26. tal change from the fusion-deep inelastic into the BDC – partic.-spect,(fireball)-like behavior.

  35. Conclusions • Mid-rapidity emissionis dominated by the pre-scissiondynamicalcontribution • Maximal heat and pressure generated in a collision closely follow reaction geometry • Head-on collisionsobey a universallinear dependenceon the available c.m. energy

  36. Conclusions • Mid-rapidity emissionis dominated by the pre-scissiondynamicalcontribution • Maximal heat and pressure generated in a collision closely follow reaction geometry • Head-on collisionsobey a universallinear dependenceon the available c.m. energy A crucial role of “hard” NN collisions

  37. Conclusions • Mid-rapidity emissionis dominated by the pre-scissiondynamicalcontribution • Maximal heat and pressure generated in a collision closely follow reaction geometry • Head-on collisionsobey a universallinear dependenceon the available c.m. energy A crucial role of “hard” NN collisions Explains theapparent controversyon the quickly establishedlocal equilibriumthroughout the compact system and completelack of global equilibration

  38. Outlook TRacing EQuilibration by ISospin (the LNS experiment C-71, spokesperson Z. Basrak) Landau-Vlasov model simulation of the isospin asymmetric 48Ca + 40Ca reaction at 40 MeV/u N/Z ratio of the quasi-projectile as a function of b

  39. N/ZQP=1.27 – 1.31 Outlook TRacing EQuilibration by ISospin (the LNS experiment C-71, spokesperson Z. Basrak) Landau-Vlasov model simulation of the isospin asymmetric 48Ca + 40Ca reaction at 40 MeV/u for b < 2 fm The same system at a similar E in the last month GANIL experiment E-503 (spokesperson A. Chibihi) N/Z ratio of the quasi-projectile as a function of b

  40. Heavy-ion dynamics at the Fermi energy A theoretical point of view RuđerBošković Institute – SUBATECH collaboration Zoran Basrak Laboratory for heavy-ion physics Division of Experimental Physics RuđerBošković Institute, Zagreb, Croatia EWON Town Meeting, May 10 –12, 2007, Prague, Czek Republic

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