Heavy-ion dynamics at the Fermi energy

1
Heavy-ion dynamics at the Fermi energy A
theoretical point of view
Ruder Boškovic Institute SUBATECH collaboration
Zoran Basrak
Laboratory for heavy-ion physics Division of
Experimental Physics Ruder Boškovic 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 field governs collision dynamics
• The Pauli blocking freezes hard . NN
  collisions

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 NN collisions

sTOT sFUS s B.P.
Still holds
sTOT sFUS
Till early 90s 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 lt 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 BDCs

• Reconstructed primary QP mass approxim. .
  equal to the projectile mass

J. Peter et al., Nucl. Phys. A593 (1995) 95.
8
QP emission in BDCs

• 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.
J. Peter et al., Nucl. Phys. A593 (1995) 95.
9
QP emission in BDCs

• 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.
J. Peter et al., Nucl. Phys. A593 (1995) 95.
10
Dynamical emission component
Landau-Vlasov model simulation
Ph. Eudes, Z. Basrak and F. Sebille, Phys. Rev.
C56 (1997) 2003.
11
Dynamical emission component
Landau-Vlasov model simulation
Ph. Eudes, Z. Basrak and F. Sebille, Phys. Rev.
C56 (1997) 2003.
12
Dynamical emission component
Landau-Vlasov model simulation
Ph. Eudes, Z. Basrak and F. Sebille, Phys. Rev.
C56 (1997) 2003.
13
Dynamical emission component
Dem ()
F. Haddad et al., Phys. Rev. C60 (1999) 031603.
System Incident energy (MeV/u)
40Ar27Al 41, 65
40Ar107Ag 50, 75, 100
107Ag40Ar 50
36Ar58Ni 52, 74, 95
12OXe129Sn 50, 75, 100
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Statistical emission component
Landau-Vlasov model simulation
The geniune primary QP emission
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Statistical emission component
Landau-Vlasov model simulation
The geniune 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.
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QP emission in BDCs
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 BDCs
pre-scission
post-scission
max. compression
Configuration space
local equilibration
max. compression
Impulse space
local equilibration
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Mid-rapidity emission in BDCs
pre-scission
post-scission
max. compression
Configuration space
local equilibration
max. compression
Impulse space
local equilibration
19
Early energy transformation
Decompression followed by abundant emission and
fast system cooling.
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Early energy transformation
System Incident energy (MeV/u) b/bmax
40Ar27Al 41, 65 0, (0.1) 1
36Ar58Ni 52, 74, 95 0, (0.2) 1
40Ar107Ag 50, 75, 100 0, (0.1) 1
12OXe129Sn 50, 75, 100 0, (0.2) 1
40Ar107Ag 20, 30, 40, 45 0
40Ar197Au 50, 75, 100 0
I. Novosel, Z. Basrak et al., Phys. Lett. B625
(2005) 26.
- Asys 70 - 250 nucl - AprojAtarg 11
15 - brel 0, (0.1) 1
Decompression followed by abundant emission and
fast system cooling.
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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.
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Head-on collisions
Dependence on available energy
I. Novosel, Z. Basrak et al., Phys. Lett. B625
(2005) 26.
28
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
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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 emission is dominated by the
  pre-scission dynamical contribution
• Maximal heat and pressure generated in a
  collision closely follow reaction geometry
• Head-on collisions obey a universal linear
  dependence on the available c.m. energy

36
Conclusions

• Mid-rapidity emission is dominated by the
  pre-scission dynamical contribution
• Maximal heat and pressure generated in a
  collision closely follow reaction geometry
• Head-on collisions obey a universal linear
  dependence on the available c.m. energy

A crucial role of hard NN collisions
37
Conclusions

• Mid-rapidity emission is dominated by the
  pre-scission dynamical contribution
• Maximal heat and pressure generated in a
  collision closely follow reaction geometry
• Head-on collisions obey a universal linear
  dependence on the available c.m. energy

A crucial role of hard NN collisions Explains
the apparent controversy on the quickly
established local equilibrium throughout the
compact system and complete lack 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
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 lt 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
Ruder Boškovic Institute SUBATECH collaboration
Zoran Basrak
Laboratory for heavy-ion physics Division of
Experimental Physics Ruder Boškovic Institute,
Zagreb, Croatia
EWON Town Meeting, May 10 12, 2007, Prague,
Czek Republic
41
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