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N/Z OF MID-RAPIDITY AND QUASI-PROJECTILE EMISSION IN 58Ni+58Ni AT 52 AMeV. TOPICS IN HEAVY ION COLLISIONS 03. D. Thériault, A. Vallée, L. Gingras, Y. Larochelle, René Roy, L. Beaulieu, F. Grenier, F. Lemieux, J. Moisan, C. St-Pierre, S. Turbide Université Laval, Québec

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  1. N/Z OF MID-RAPIDITY AND QUASI-PROJECTILE EMISSION IN 58Ni+58Ni AT 52 AMeV TOPICS IN HEAVY ION COLLISIONS 03 • D. Thériault, A. Vallée, L. Gingras, Y. Larochelle, René Roy, L. Beaulieu, • F. Grenier, F. Lemieux, J. Moisan, C. St-Pierre, S. Turbide • Université Laval, Québec • - INDRA Collaboration, France • - Sherry Yennello’s Group, Texas A&M Univesity OUTLINE • Mid-rapidity emission in heavy ion collisions at intermediate energies • Source reconstruction • Free nucleon multiplicities • Neutron/proton ratio of complete nuclear matter: MRS and QP • Conclusion

  2. HEAVY ION COLLISIONS AT INTERMEDIATE ENERGIES (20-100 AMeV) BINARY DISSIPATIVE REACTIONS Target Projectile MRS QT E* QP E* MRS: L. Gingras et al., Phys. Rev. C 65, 061604(2002)

  3. NEUTRON ENRICHMENT AT MID-RAPIDITY? AS A FUNCTION OF CENTRALITY: - N/Z OF COMPLETE MRS NUCLEAR MATTER - N/Z OF COMPLETE QP NUCLEAR MATTER COMPLETE NUCLEAR MATTER = BOUND PARTICLES (A≥2) + FREE PROTONS + FREE NEUTRONS VELOCITY RECONSTRUCTION 58NI + 58NI 52 AMeV INDRA MULTISOURCE FIT 58NI + 58NI 52 AMeV INDRA MULTISOURCE FIT 36Ar + 58NI 50 AMeV HERACLES

  4. 58Ni + 58Ni 52 AMeV Isotopic resolution Z≤4 Charity evaporation attractor line 5≤Z≤24 N/Z of system (1.07) Z≥25 INDRA AT GANIL, FRANCE Plastics (phoswichs) Ionisation chambers Silicons CsI (Tl)

  5. SOURCES SELECTION (A≥2) QP QT MRS Vrel VQT 2 cm/ns Vres BEAM DIRECTION • Dividing Vrel forward distribution by backward distribution, • probability tables are built for backward distribution QP attribution. • Probability tables are usedevent by event for backward distribution QP attribution.

  6. BOUND NUCLEONS IN MRS (A≥2) 58Ni + 58Ni at 52 AMeV QP MRS Neutrons Protons ------ Neutrons Protons ------ SMR Graphs exclude free nucleons and QP residue

  7. FREE NUCLEONS • Great overlap in velocity distributions • - Multisource fit technique is used Laboratory frame: Avec: where Es is the kinetic energy of a nucleon at rest in a source frame moving at Vs and θ is the detection angle Each source (QP,QC,SMR) has 4 parameters to fit: T(temperature), VS(velocity), BC(Coulomb barrier) and N (multiplicity).

  8. Free protons energy spectras 58Ni + 58Ni at 52 AMeV ….. MRS ---- QP QC TOTAL QP MRS

  9. FREE NEUTRONS IN 36Ar + 58Ni AT 50 AMeV HERACLES Multidetector, Université Laval, + neutron detectors Cyclotron Institute, Texas A&M University. 105O 60O 120O 45O Heracles Array BEAM TARGET 150O 135O 75O 90O Neutron detectors BC-501

  10. FREE NEUTRONS ENERGY SPECTRAS 36Ar + 58Ni 50 AMeV ….. ---- QT MRS TOTAL MRS QT

  11. LINK BETWEEN 36Ar+58Ni AND 58Ni+58Ni FOR FREE NEUTRONS THE LINK IS EXCITATION ENERGY PER NUCLEON FOR QT IN (36Ar+58Ni) AND QP IN (58Ni+58Ni). IS USED RELATION :QP 58Ni+ 58Ni 52 AMeV :QP 40Ar+27Al 40 AMeV # #G. Lanzano et al., Nucl. Phys. A683, 566(2001)

  12. N/Z RATIOS (QP AND MRS) 58Ni+58Ni 52 AMeV --------- N/Z=1.07 N/Z MRS N/Z QP

  13. CONCLUSION - Progressive neutron enrichment (with centrality) of MRS nuclear matter. • N/Z ratio of the complete MRS nuclear material reaches a value higher • than the initial system’s one (1.07) and that of the QP which decreases • around 1. • An experiment detecting neutron multiplicities and charged particles • in the same setup would greatly improve precision on MRS N/Z • measurement.

  14. PROJECTILE RECONSTRUCTED MASS AND CHARGE 58Ni+58Ni 52 AMeV Neutron nb. Proton nb. Neutron nb. N/Z=1.07

  15. MISSING NEUTRONS TO RECOVER PROJECTILE N/Z (1.07) * BUU simulations (b=3fm - 4.5 fm) (neutronMRS 58Ni+58Ni / neutronMRS 36Ar+58Ni = 1.86) Neutron nb.

  16. N/Z RATIOS (QP AND SMR) IN 58Ni+58Ni AT 52 AMeV WITH CORRECTION FOR FREE NEUTRONS IN SMR N/Z MRS N/Z QP ------- N/Z=1.07

  17. ETL HYPOTHESIS FOR NEUTRON MULTIPLICITIES

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