1. Mid-peripheral collisions : PLF* decay
Sylvie Hudan, Indiana University P T
TLF*
PLF*
1 fragment
vL > vH
forward
vH > vL
backward
More than 2 fragments

2. Step by step Correlation Size - Velocity Experimental setup
The simplest case : 1 heavy fragment
Binary breakups : statistical vs. dynamical
Summary & Outlook

3. Fragments from the PLF*
Ta+Au 33 MeV/A
INDRA data
J. Normand, J. Colin and D. Cussol
ZMAX
Z MAX-1
Z MAX-2
Z MAX-3
« Hierarchy of the velocity and of the angular distribution of the fragments as a fonction of their charge »

4. Comparison with a model : Classical N-Body Dynamics
« As in the data, the heaviest fragment is the fastest and is aligned along the QP velocity »
D. Cussol, PRC65, (2002)

5.  Detection of charged particles in 4p
Experimental setup
114Cd + 92Mo at 50 A.MeV
LASSA : Mass resolution up to Z=9
7  lab  58
Beam
Ring Counter :
Si (300 m) – CsI(Tl) (2cm)
2.1  lab  4.2
1 unit Z resolution
Mass deduced†
Drawing of the setup Resolution in the RC Reaction
Projectile 48
Miniball/Miniwall
 Detection of charged particles in 4p
† : Modified EPAX
K. Sümmerer et al., Phys. Rev. C42, 2546 (1990)

6. Events with one heavy fragment from a PLF*
PLF frame
30  ZPLF*  46
Well-defined emission from the PLF

7. One fragment : Isotropic component
PLF frame
Other component
(mid-rapidity, …)
Isotropic component

8. One fragment : reconstruction of the PLF*
Fit of the isotropic component
At  = 90, alpha particles
 20% of non-statistical emission
Mevap = 6.97
Zevap = 10.6
ZPLF + Zevap   46
(Zprojectile = 48)

9. One fragment : temperatures
Data : slope temperature
Simon : emission temperature
Simon* :
A = 109
E*  500 MeV
J = 0 hbar
* : D. Durand, Nucl. Phys. A541, 266 (1992)
Lower slope temperature for protons and alpha particles

10. Velocity damping and excitation energy
Strong correlation between
the multiplicity of evaporated particles
and the velocity damping
 Strong correlation between the slope temperature and the velocity damping
 Velocity damping correlated to E*

11. Events with two fragments from a PLF*ZH ZL
vL > vH, forward
vH > vL , backward
PLF*
Statistical behavior  isotropy  vH > vL  vL > vH

12. Two fragments : anisotropy of PLF* decay
6  NC  10
B. Davin et al., Phys. Rev. C65, (2002)
 Different charge splits
 more asymmetric split for the backward case
Zh – Zl correlation Angle between vrel and vplf* Vrel vs Zl
 Different alignments
 more alignment for the backward case

13. Two fragments : relative velocities
6  NC  10
B. Davin et al., Phys. Rev. C65, (2002)
Zh – Zl correlation Angle between vrel and vplf* Vrel vs Zl
 Different relative velocities
 higher vrel for the backward case
 Dependence with the size for the backward case

14. Asymmetry of the breakup : Sensitivity to vPLF*
6  NC  10
vL > vH
vH > vL
vPLF*
9.2
8.9
8.3
8.6
E*,J
x100
x20 x2
x80
x10 x1
More asymmetric Z distribution for the backward case
Higher asymmetry at high vPLF* (low E*,J)
For all vPLF* , asymmetry for the backward case
 An other degree of freedom?
Z distribution for different cut in Vplf* Point : Vplf* seems to be a good observable
vprojectile = 9.45 cm/ns
B. Davin et al., Phys. Rev. C65, (2002)

15. To summarize… The forward and backward cases are different :
Forward emission is consistent with standard statistical emission
Backward emission is consistent with dynamical decay
Different charge split  dynamical has higher asymmetry
Different alignment  dynamical is more aligned
Different relative velocity for the same ZL
 dynamical has higher vrel
Different Z distribution for a given (E*,J)

16. Well-defined PLF* : ZPLF* and vPLF*
dynamical
statistical
More dissipation and fluctuations as ZPLF* decreases
For a given size, less dissipation for the dynamical case
Justification of Vplf* as a good observable
vL > vH
vH > vL
Same correlation
expected if vPLF* and E* correlated

17. Opening channels
1 fragment (x 0.1)
vL > vH
vH > vL
Proba as a function of Vplf* Coulomb barrier explanation
 Dynamical emission opens at higher vPLF* , i.e. lower E*
Up to 10% of the cross-section in the 2 fragment decay

18. Asymmetry and Coulomb barrier
35  ZPLF*  39
Higher asymmetry for the dynamical case
Coulomb barrier lower
Dynamical case appears at lower E*

19. Energy in the fragments
TKE vs Vplf*
More kinetic energy in the 2 fragments for the dynamical case
For a given vPLF*, difference of  MeV

20. A statistical picture : Viola systematics
Comparison statistical / Viola
At large vPLF*,
statistical  Viola
 Deviation for low vPLF*
 Temperature ?
Comparison dynamical / Viola
 For all vPLF*, dynamical >>Viola
 More compact shape needed for the dynamical case
Comparison TKE exp. and Viola syst. Radius para. needed in Viola to reproduce data (Suggest more compact shape)

21. Estimation of the temperature
Measured
Estimated
(Viola systematic)
Statistical case : vL > vH
Temperatures between 0 and 10-12 MeV
These temperatures are consistent with T=7 MeV from the isotopes in LASSA
(for 30  ZPLF*  46)

22. To summarize… vPLF* as a good observable :
Same correlation (vPLF*)-vPLF* for statistical and dynamical cases
Dynamical case appears at higher vPLF* Coulomb barrier effect
 vPLF* (TKE)dynamical > (TKE)statistical by  MeV
Statistical  Viola at high vPLF* and deviation with increasing vPLF*
Temperature
Dynamical case always underestimated by Viola

23. A law : energy conservationZH ZL
PLF* +
E* , BEPLF*
TKEH , BEH
TKEL , BEL
TKEevap , BEevap
Statement to say that we should have Einit = Efinal
For a selected vPLF*  E*
Kinetic energy in the fragments
 Higher for the dynamical case
Q value
Evaporated particles

24. “Missing” energy : Q value?
Q vs Vplf*
Same Q value in both cases for all vPLF*

25. “Missing” energy : evaporation?
Multiplicity of Z=2 emitted forward to the PLF* (in LASSA)
vL > vH
vH > vL
statistical
dynamical
Multiplicity of Z=2 forward to the PLF : Distribution Average value + deviation
Dependence of the multiplicity with VPLF* (E*)
Higher average multiplicities for the statistical by 10-20%

26. Energy conservation : balance
vPLF* fixed
Fixed
for Z=2
Longer time scale in the statistical case ?
Neutrons
Evaporation before/after breakup

27. A picture of the process
TKE
Time
Saddle-point
Scission-point
Initial kinetic energy? Q
Coulomb
Collective
“Extra” energy
Fluctuations of TKE
(Q+Coulomb)-TKE correlation

28. TKE : width of the distribution
Sigma(TKE) vs. Vplf* Statistical explanation (asymmetry effect?)
More fluctuations in the dynamical case
consistent with an additional kinetic energy at the scission-point

29. Conversion : Q + Coulomb to TKE
TKE vs Q : fit of the slope
Statistical
TKE  Q + Coulomb
Dynamical
TKE  Q + Coulomb + E0

30. Conclusions : building a coherent picture
We interpreted…
We observed…
Correlation (vPLF*)-vPLF*
Correlation vPLF* - Mevap
Multiplicities of evaporated Z=2
Different TKE for all vPLF*
Different TKE for all vPLF*
Correlation TKE-(Q+Coulomb)
vPLF* good selector for E*
scission,dynamical < scission,statistical
Initial TKE at scission
for the dynamical case is larger than the statistical case

31. Influence of the target
INDRA data
J. Normand, J. Colin and D. Cussol L H Z + - = h
relative velocity

32. Ratio of the standard fission
REVERSE Data preliminary results
Nautilus Data
F.Bocage et al., NPA676 (2000) 391
« For heavy systems the importance of the isotropic component depends on:
the size of the PLF(fissility)
the size of the target
the incident energy »

33. Summary & Outlooks Process with a big cross-section
Same process for the most central collisions?
Description by a model : need of a dynamical description
C.P. Montoya et al., Phys. Rev. Lett. 73, 3070 (1994)
B. Davin et al., Phys. Rev. C65, (2002)
S. Piantelli et al., Phys. Rev. Lett. 88, (2002)
F. Bocage et al., Nucl. Phys. A65, 391 (2000)
J. Colin et al., in preparation

34. Collaboration S. Hudan , B. Davin, R. Alfaro, R. T. de Souza, H. Xu,
L. Beaulieu, Y. Larochelle, T. Lefort, V. Viola and R. Yanez
Department of Chemistry and Indiana University Cyclotron Facility,
Indiana University, Bloomington, Indiana 47405
R. J. Charity and L. G. Sobotka
Department of Chemistry, Washington University, St. Louis, Missouri 63130
T. X. Liu, X. D. Liu, W. G. Lynch, R. Shomin, W. P. Tan, M. B. Tsang,
Vander Molen, A. Wagner, H. F. Xi, and C. K. Gelbke
National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy,
Michigan State University, East Lansing, Michigan 48824

35. Specials Thanks To … Jacques Normand Jean Colin Daniel Cussol
Thesis in 2001, LPC Caen, FRANCE
Jean Colin
Daniel Cussol