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- Mid-rapidity emission in heavy ion Mid-rapidity emission in heavy ion collisions at intermediate energiescollisions at intermediate energies- Source reconstructionSource reconstruction- Free nucleon multiplicities Free nucleon multiplicities - Neutron/proton ratio of complete nuclear matter: MRS and QPNeutron/proton ratio of complete nuclear matter: MRS and QP- ConclusionConclusion
-D. Thériault, A. Vallée, L. Gingras, Y. Larochelle, René Roy, L. Beaulieu, 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, QuébecUniversité Laval, Québec
- INDRA Collaboration, France- INDRA Collaboration, France
- Sherry Yennello’s Group, Texas A&M Univesity- Sherry Yennello’s Group, Texas A&M Univesity
HEAVY ION COLLISIONS AT INTERMEDIATE ENERGIES (20-100 AMeV)HEAVY ION COLLISIONS AT INTERMEDIATE ENERGIES (20-100 AMeV)BINARY DISSIPATIVE REACTIONSBINARY DISSIPATIVE REACTIONS
QP E*QT E*MRS
ProjectileTarget
MRS: L. Gingras et al., Phys. Rev. C 65, 061604(2002)
AS A FUNCTION OF CENTRALITY:AS A FUNCTION OF CENTRALITY:
- - N/ZN/Z OF OF COMPLETE MRSCOMPLETE MRS NUCLEAR MATTER NUCLEAR MATTER
- - N/ZN/Z OF OF COMPLETE QPCOMPLETE QP NUCLEAR MATTER NUCLEAR MATTER
NEUTRON ENRICHMENT AT MID-RAPIDITY?NEUTRON ENRICHMENT AT MID-RAPIDITY?
COMPLETE NUCLEAR MATTERCOMPLETE NUCLEAR MATTER
==BOUND PARTICLES (ABOUND PARTICLES (A≥2) ≥2)
++FREE PROTONSFREE PROTONS
++FREE NEUTRONSFREE NEUTRONS
VELOCITY RECONSTRUCTION58NI + 58NI 52 AMeV INDRA
MULTISOURCE FIT58NI + 58NI 52 AMeV INDRA
MULTISOURCE FIT36Ar + 58NI 50 AMeV HERACLES
5858Ni + Ni + 5858Ni 52 AMeVNi 52 AMeV
INDRA AT GANIL, FRANCEINDRA AT GANIL, FRANCE
Ionisation chambers
Plastics (phoswichs)
Silicons
CsI (Tl)
Isotopic resolution Z≤4Charity evaporation attractor line 5≤Z≤24N/Z of system (1.07) Z≥25
SOURCES SELECTIONSOURCES SELECTION
Vrel
BEAM DIRECTION
VresVQT 2 cm/ns
QT MRS QP
(A≥2)
- Dividing Vrel Dividing Vrel forward distribution forward distribution by by backward distribution, , probabilityprobability tables are built for tables are built for backward distribution QP QP attribution. attribution.
- Probability tables are usedProbability tables are used event by event for event by event for backward distribution QP attribution. QP attribution.
BOUND NUCLEONS IN MRS (A≥2)BOUND NUCLEONS IN MRS (A≥2)
SMR
Graphs exclude free nucleons and QP residueGraphs exclude free nucleons and QP residue
MRSMRSQPQP
5858Ni + Ni + 5858Ni at 52 AMeVNi at 52 AMeV
NeutronsProtons
------ NeutronsProtons
------
FREE NUCLEONSFREE NUCLEONS
- Great overlap in velocity distributionsGreat overlap in velocity distributions
- Multisource fit technique is usedMultisource fit technique is used
TBcEeBcET
NvolumedEd
Nd /)()(2/3)(2)(
2
TBcEeBcET
NsurfacedEd
Nd /)()(24)(
2
'22/1
'
2EE
dEd
Nd
ElabE
labdEd
Nd
Laboratory frame:
Avec: SSlablab EEEEE cos2/12/12'
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).
Free protons energy spectras Free protons energy spectras 5858Ni + Ni + 5858Ni at 52 AMeVNi at 52 AMeV
---- QP ….. QC TOTALMRS
QPMRS
FREE NEUTRONS IN FREE NEUTRONS IN 3636Ar + Ar + 5858Ni AT 50 AMeVNi AT 50 AMeV
HERACLES Multidetector, Université Laval, + neutron detectorsHERACLES Multidetector, Université Laval, + neutron detectorsCyclotron Institute, Texas A&M University.Cyclotron Institute, Texas A&M University.
45O
60O105O
120O
75O
90O
135O
150O
BEAM
Neutron detectors BC-501Neutron detectors BC-501
TARGET
Heracles Array
FREE NEUTRONS ENERGY SPECTRAS FREE NEUTRONS ENERGY SPECTRAS 3636Ar + Ar + 5858Ni 50 AMeVNi 50 AMeV
---- QT ….. MRS TOTAL
MRS
QT
LINK BETWEEN LINK BETWEEN 3636Ar+Ar+5858Ni AND Ni AND 5858Ni+Ni+5858Ni FOR FREE NEUTRONSNi FOR FREE NEUTRONS
proj
resproj
Z
ZZCQP
A
E *
THE LINK IS EXCITATION ENERGYTHE LINK IS EXCITATION ENERGY PER NUCLEON FOR QT IN PER NUCLEON FOR QT IN ((3636Ar+Ar+5858Ni) AND QP IN (Ni) AND QP IN (5858Ni+Ni+5858Ni).Ni).
RELATIONRELATION IS USEDIS USED
:QP 58Ni+ 58Ni 52 AMeV:QP 40Ar+27Al 40 AMeV #
#G. Lanzano et al., Nucl. Phys. A683, 566(2001)
N/Z RATIOS (QP AND MRS) N/Z RATIOS (QP AND MRS) 5858NiNi+58+58Ni 52 AMeVNi 52 AMeV
N/Z MRS N/Z QP --------- N/Z=1.07
CONCLUSIONCONCLUSION
- 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 particlesAn 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.
PROJECTILE RECONSTRUCTED MASS AND CHARGE PROJECTILE RECONSTRUCTED MASS AND CHARGE 5858NiNi+58+58Ni 52 AMeVNi 52 AMeV
Proton nb. Neutron nb. Neutron nb. N/Z=1.07
MISSING NEUTRONS TO RECOVER PROJECTILE N/Z (1.07)MISSING NEUTRONS TO RECOVER PROJECTILE N/Z (1.07)
Neutron nb. * BUU simulations (b=3fm - 4.5 fm)
(neutronMRS 58Ni+58Ni / neutronMRS
36Ar+58Ni = 1.86)
N/Z RATIOS (QP AND SMR) IN N/Z RATIOS (QP AND SMR) IN 5858NiNi+58+58Ni AT 52 AMeVNi AT 52 AMeVWITH CORRECTION FOR FREE NEUTRONS IN SMRWITH CORRECTION FOR FREE NEUTRONS IN SMR
N/Z MRS N/Z QP ------- N/Z=1.07