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Mid-peripheral collisions : PLF* decay

Mid-peripheral collisions : PLF* decay. T. TLF *. P. PLF *. More than 2 fragments. v L > v H forward. 1 fragment. v H > v L backward. Sylvie Hudan, Indiana University. Step by step. Correlation Size - Velocity Experimental setup The simplest case : 1 heavy fragment

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Mid-peripheral collisions : PLF* decay

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

  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 Z MAX-1 Z MAX-2 Z MAX-3 ZMAX INDRA data J. Normand, J. Colin and D. Cussol « 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, 054614 (2002)

  5. Experimental setup 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† 48 Projectile 114Cd + 92Mo at 50 A.MeV 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  35 +10.6  46 (Zprojectile = 48)

  9. One fragment : temperatures Data : slope temperature Simon* : A = 109 E*  500 MeV J = 0 hbar Simon : emission temperature * : 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* ZL ZH vL > vH, forward PLF* ZH vH > vL , backward ZL Statistical behavior  isotropy  vH > vL vL > vH

  12. Two fragments : anisotropy of PLF* decay 6  NC 10 B. Davin et al., Phys. Rev. C65, 064614 (2002) Different charge splits more asymmetric split for the backward case Different alignments more alignment for the backward case

  13. Two fragments : relative velocities 6  NC 10 B. Davin et al., Phys. Rev. C65, 064614 (2002) 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* vPLF* vL > vH vH > vL 9.2 x80 x100 x20 x10 8.9 x2 x1 8.6 8.3 E*,J 6  NC 10 • 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? vprojectile = 9.45 cm/ns B. Davin et al., Phys. Rev. C65, 064614 (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 vL > vH vH > vL dynamical • Same correlation expected if vPLF* and E* correlated • More dissipation and fluctuations as ZPLF* decreases • For a given size, less dissipation for the dynamical case

  17. Opening channels vL > vH vH > vL 1 fragment (x 0.1)  Dynamical emission opensat 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 • More kinetic energy in the 2 fragments for the dynamical case • For a given vPLF*, difference of  20-30 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

  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  20-30 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 For a selected vPLF* E* • Kinetic energy in the fragments  Higher for the dynamical case • Q value • Evaporated particles

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

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

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

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

  28. TKE : width of the distribution • More fluctuations in the dynamical case consistent with an additional kinetic energy at the scission-point

  29. Conversion : Q + Coulomb to TKE 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 TKEfor 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 relative velocity - Z Z h = H L + Z Z H L

  32. Ratio of the standard fission F.Bocage et al., NPA676 (2000) 391 Nautilus Data REVERSE Data preliminary results « 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, 064614 (2002) S. Piantelli et al., Phys. Rev. Lett. 88, 052701 (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 Thesis in 2001, LPC Caen, FRANCE Jean Colin Daniel Cussol

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