1. - 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 -D. Thériault, A. Vallée, L. Gingras, Y. Larochelle, René Roy, L. Beaulieu, F. Grenier, F. Lemieux, J. Moisan, C. St-Pierre, S. Turbide F. Grenier, F. Lemieux, J. Moisan, C. St-Pierre, S. Turbide Université Laval, Québec Université Laval, Québec - INDRA Collaboration, France - Sherry Yennello’s Group, Texas A&M Univesity

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

17. ETL HYPOTHESIS FOR NEUTRON MULTIPLICITIES