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Mid-peripheral collisions : PLF* decay

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Presentation on theme: "Mid-peripheral collisions : PLF* decay"— Presentation transcript:

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 conservation
ZH 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


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