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Mid-peripheral collisions : PLF* decay

Mid-peripheral collisions : PLF* decay. T. TLF *. P. PLF *. v L > v H forward. v H > v L backward. 1 fragment. Sylvie Hudan, Indiana University. Statistical behavior  isotropy  v H > v L  v L > v H. Experimental setup. LASSA : Mass resolution up to Z=9

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Mid-peripheral collisions : PLF* decay

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  1. Mid-peripheral collisions : PLF* decay T TLF* P PLF* vL > vH forward vH > vL backward 1 fragment Sylvie Hudan, Indiana University Statistical behavior  isotropy  vH > vL vL > vH

  2. 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† † : Modified EPAX K. Sümmerer et al., Phys. Rev. C42, 2546 (1990) 48 Projectile 114Cd + 92Mo at 50 A.MeV Miniball/Miniwall  Detection of charged particles in 4p

  3. Events with two fragments from a PLF* ZL ZH vL > vH, forward PLF* ZH vH > vL , backward ZL

  4. Anisotropy of PLF* decay Different charge splits more asymmetric split for the backward case Different relative velocities higher vrel for the backward case Different alignments more alignment for the backward case 6  NC 10 B. Davin et al., Phys. Rev. C65, 064614 (2002)

  5. Asymmetry of the breakup :Sensitivity to vPLF* vPLF* vL > vH vH > vL 9.2 x80 x100 x20 8.9 x10 x2 8.6 x1 8.3 E*,J 6  NC 10 B. Davin et al., Phys. Rev. C65, 064614 (2002) • 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

  6. 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)

  7. 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

  8. Opening channels 1 fragment (x 0.1) vL > vH vH > vL  Dynamical emission opensat higher vPLF* , i.e. lower E* • Up to 10% of the cross-section in the 2 fragment decay

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

  10. Energy in the fragments • More kinetic energy in the 2 fragments for the dynamical case • For a given vPLF*, difference of  20-30 MeV

  11. 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

  12. 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)

  13. To summarize… • vPLF* as a good observable : • Samecorrelation(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

  14. 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

  15. “Missing” energy : Q value? (MeV) • Same Q value in both cases for all vPLF*

  16. “Missing” energy : evaporation? vL > vH statistical vH > vL dynamical Multiplicity of Z=2 emitted forward to the PLF*(in LASSA) • Higher average multiplicities for the statistical case • Deviation of 10-20%

  17. Energy conservation : balance Fixed vPLF* fixed for Z=2 Suggests a longer time scale in the statistical case

  18. 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

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

  20. Conversion : Q + Coulomb to TKE Statistical TKE  Q + Coulomb Dynamical TKE  Q + Coulomb + E0

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

  22. 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

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