1. Isospin dependence of nucleus-nucleus collisions
Martin Veselský
Institute of Physics of Slovak Academy of Sciences, Bratislava, Slovakia

2. Variation of isospin asymmetry ( N/Z - ratio ) in nucleus-nucleus collisions
- access to the limits of nuclear stability and production of exotic nuclei
- influence of isospin asymmetry on reaction scenarios
- isospin dependence of nuclear equation of state

3. Exotic nuclei
- only 2500 out of approx 6000 possible nuclei known
- large region of very neutron-rich nuclei still unknown
- region of superheavy nuclei
Physics questions
- properties of nuclear surface
( neutron skin )
- nuclear astrophysics ( r-process )
- hyperheavy nuclei, nuclear molecules

4. Production of proton-rich nuclei - complete fusion + ISOL technique

5. Superheavy nuclei -
up to Z=112 produced in cold fusion ( Pb, Bi-target, 1n-channel ),
heavier nuclei produced in hot fusion ( 3-4n-channel )

6. FRS
Production of exotic nuclei in relativistic fragmentation
Separator FRS ( GSI Darmstadt ), beam energy 1 GeVA,
Separátor LISE ( GANIL ), beam energy MeVA.

7. Observed excess of neutron-rich nuclei
in reactions 86Kr+64Ni at 25 AMeV ( right )
and 124Sn+124Sn pri 20 AMeV ( left ).
Experiments at fragment separator MARS
( Cyclotron Lab, Texas A&M University ).

9. EURISOL - 6FP Project "EURISOL Design Study" started in Feb 2005
( MV/Bratislava involved )
- theoretical and experimental studies of production mechanisms
are planned
- open question - Heavy Ion capability for driver accelerator - yes or no ?
- selection of the key experiment(s)

11. How to reach the extremely neutron-rich nuclei:
- What is the optimum beam energy ? Lower than 20 AMeV ?
- Two-step scenario ?

12. Fragment separator VAMOS ( GANIL Caen )
- angular acceptance 9 deg for beam energies AMeV.

13. Production of extremely neutron-rich nuclei - two-step process.
Experiment approved at GSI ( a part of EURISOL effort ).
Primary target
Separation of secondary beam
Secondary target
Identification of final products

14. Nucleus-nucleus collisions at beam energies below 100 AMeV:
- peripheral elastic and quasi-elastic ( QE ) collisions
- semi-peripheral deep-inelastic collisions ( DIT ) collisions
- incomplete ( ICF ) and complete ( CF ) fusion in central collisions
- pre-equilibrium emision typically preceding ICF/CF and DIT
( for details see M. Veselský, Nuclear Physics A 705(2002)191 )

15. Participant-spectator reactions at relativistic energies ( above 100 AMeV )

16. Central collisions
reaction: 124Sn+27Al at 20 AMeV ( M. Veselsky et al., NPA 724 (2003) 431 )
test of the model description of central collisions
( M. Veselsky, NPA 705 (2002) 193 )

17. Model description ( M. Veselsky, NPA 705 (2001) 191 ) :
- classical Coulomb trajectories assumed
- pre-eq. emission multiplicity proportional to maximum overlap
- participant-spectator scenario assumed at maximum overlap
- incomplete fusion of the participant zone with one of the spectators

18. PE+DIT/ICF+GEMINI
PE+DIT/ICF+SMM
124Sn+27Al at 20 AMeV

19. Single source: 144Nd, E*=310 MeV, v=0.17c
A=65-75

20. Conclusions - 124Sn+27Al at 20 AMeV
- description of central collision as PE+ICF is consistent, including
kinematics and isospin asymmetry of heavy residues
- SMM ( multifragmentation ) describes the de-excitation of hot
nuclei better than GEMINI ( sequential binary decay )

21. Peripheral collisions ( M. Veselsky, G. Souliotis, nucl-th/0507026 ) :
reactions 86Kr + 64Ni, 112,124Sn at 25 AMeV
effect of nuclear periphery ( neutron skin ? )

22. 86Kr + 64Ni at 25 AMeV
Standard DIT ( Tassan-Got and Stefan, NPA 524 (1991) 121 )
solid - GEMINI, dash -SMM

23. 86Kr + 64Ni at 25 AMeV Modified DIT (nucl-th/0507026): ...
S... = S...exp - S...mac ,  = 0.53, s > 0
solid - GEMINI, dash -SMM
Correlation of skin thickness
to isovector chemical potential
(V. Kolomietz et al, PRC 64(2001)024315)

24. 86Kr + 124Sn at 25 AMeV Standard DIT ( Tassan-Got )
Modified DIT (nucl-th/ ):
solid - GEMINI, dash -SMM

25. 86Kr + 112Sn at 25 AMeV Standard DIT ( Tassan-Got )
Modified DIT (nucl-th/ ):
solid - GEMINI, dash -SMM
dash-dotted - SMM, s > 0.8 fm

26. Conclusions 86Kr + 64Ni, 112,124Sn at 25 AMeV
- a correction to DIT describes the effect of isospin asymmetry
at nuclear periphery
- inversion of the bulk isospin flow due to microscopic structure
- consistent parameters  for all reactions
- SMM reproduces the yields of n-rich species well while
overestimating the yields of -stable isotopes close to the projectile
- GEMINI typically overestimates the width of mass distributions
- for p-rich target 112Sn stronger Coulomb interaction supresses
the effect of isospin asymmetry at nuclear periphery at s < 1 fm

27. 18O + 181Ta at 35 AMeV, carbon isotopes
Experiment (COMBAS)
PE+DIT/ICF+SMM
18O + 181Ta at 35 AMeV, carbon isotopes

28. 18O + 181Ta at 35 AMeV, beryllium isotopes
Experiment (COMBAS)
PE+DIT/ICF+SMM
7Be
7Be
18O + 181Ta at 35 AMeV, beryllium isotopes
7Be - fast component, intense pre-eq emission, ICF kinematically
impossible, motion along classical Coulomb trajectory ? Transparency ?

29. Phase diagram of nuclear matter

30. demonstration of phase transition in dilute nuclear matter ?
Multifragmentation-
demonstration of phase transition
in dilute nuclear matter ?
Sauer, Chandra, Mosel, NPA 264(1976)221

31. First order phase transition ?
Pochodzalla et al. PRL 75(1995)1040
First order phase transition ?
GANIL data

32. Isospin-asymmetric liquid-gas phase transition
( figures from Muller, Serot, PRC 52(1995)2072 ).

33. Yield ratios and temperature
M. Veselsky et al., PLB 497 (2001) 1.
T(2,3H/3,4He)
T(3H/3He)
Yield ratios and temperature

34. LCP
IMF
Distribution of isospin between phases ( M. Veselský et al., PRC 62(2000)41605 )

35. Isoscaling in nuclear processes
M.B. Tsang et al., PRL 86(2001)5023
G. Souliotis et al., PRC 68(2003)24605
Isoscaling in nuclear processes
M. Veselský et al., PRC 69(2004)44607

36. Isoscaling, chemical potencials, phase separation
M. Veselský et al., PRC 69(2004)31602.

37. Correlated signals of phase transition -
M. Veselsky et al., NPA 749 (2005) 114c.

38. Kinematic temperatures - signal of equilibration with nucleon gas

39. Conclusions:
- way to extremely neutron-rich nuclei has still to be found
- interesting effects can be observed when comparing high
resolution experimental data to precise simulations
- tracing of isospin evolution is complicated by de-excitation
- microscopic structure at nuclear periphery leads to isospin
evolution away from isospin equilibrium
- transparent mean field ?
- isospin-asymmetric liquid-gas phase transition indicated
by correlated signals such as evolution of chemical potentials,
caloric curve and kinematic temperatures of fragments

40. Extras

41. D. Henzlova et al, nucl-ex/0507003