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Laboratory for Nuclear PhysicsLaboratory for Nuclear Physics Division of Experimental Physics Division of Experimental Physics RRuđeruđer Bošković Bošković Institute, Zagreb, CroatiaInstitute, Zagreb, Croatia
Zoran Basrak
11th International Conference on Nucleus-Nucleus Collisions May 28 – June 1st, 2011, San Antonio, TX–USA
Philippe Eudes, Maja Zorić, and François SébilleIn collaboration withIn collaboration with
Landau-Vlasov simulationTransport equation of the Boltzmann type
H = T+U, U = Vnucl+VCoul ,
Vnucl – Gogny G1-D1 non-local potential K=228 MeV, m*/m=0.67
f = f(r,p;t) - distribution function
Collision termPhenomenological, isotropic σ = σ(E, iso) [Chen et al.]
An approach adequate for bulk (one-body) properties of nuclear dynamics, in particular for an early and compact reaction phase
Dynamical emission component
P. E
u des
, Z. B
asra
k an
d F
. Seb
i lle
, Ph y
s. R
ev. C
56 (
199 7
) 20
0 3.Landau-Vlasov model
simulation
Ar ( 65 MeV / u ) Al
Ar ( 65 MeV / u ) Al A similar two-stages processin 1A GeV range by EOS CollJ.A. Hauger et al. PRL 77 (1996) 235.
A similar conclusion valid forany reaction below 100A MeV
A HI collision is decisively governed by the early and compact reaction stage.
In violent collisions during this compactreaction phase an important mass andenergy is evacuated from system.
An early energy transformation should should be studied in more detailbe studied in more detail.
Early reaction phase
Early energy transformation
Etot = Ecollect + Eintrin Eintrin = Eexcit + Epotent
Eexcit EExx//AA
Decompression followed by abundant emission and fast system cooling.
Asys = ~60 - ~400 nucl
Aproj:Atarg = 1:1 – 1:5
System Incident energy (MeV/u)
40Ar+27Al 25, 41, 53, 65, 77, 99
36Ar+58Ni 52, 74, 95
40Ar+107Ag 20, 30, 40, 45, 50, 75, 100
40Ar+197Au 50, 75, 100
36Ar+36Ar 32, 40, 52, 74
58Ni+58Ni 52, 74, 90
12OXe+129Sn 25, 32, 39, 45, 50, 75, 100
197Au+197Au 20, 30, 40, 60, 80, 100
Evolution of excitation energy
– Regular rise & fall with time at each EIN
– Width & height regularlybehave as a f(EIN)
Evolution of excitation energy
– Regular rise & fall with time at each EIN
– Width & height regularlybehave as a f(EIN)
– Maxima reflect the totalenergy deposited inthe reaction system
Excitation energy maxima
Eproj
Aproj
Eavail = Atarg Aproj
(Atarg+Aproj)2
Ex as a fraction of EAVAIL
– Fraction is almost constant over a wide energy range
– Large variety of systems
Experimental excitation energy In HIR excitation energy Ex is not directly
accessible.
Calorimetry. Various corrections for issues which are not under control. Often one resorts to theoretical predictions.
To obtain Ex/A besides the total excitation energy also the mass of the primary emission source has to be estimated.
One must add a problem of selecting events according to reaction centrality.
One cannot expect a most direct compa-One cannot expect a most direct compa- rizon simulation – experiment rizon simulation – experiment
All available data onEx/A in central HIcollisions in the last20 years
Experimental excitation energy
Experimental excitation energyAll available data onEx/A in central HIcollisions in the last20 years– Strong spread of the data points– Connected data points of the same measurement– Close to linear dependence on EIN
Data for EIN > 100A MeV
W. R
eisd
orf
et a
l ., N
ucl .
Ph y
s. A
848
(20 1
0) 3
66.
– Radial flow of light reaction products deduced on two manners– Some correction relative to FOPI PHASE 1 but still a linear function of EIN
Radial flow deduced by blast model.
Remaining energy is taken as thermal.
W. R
eisd
orf
et a
l ., N
ucl .
Ph y
s. A
612
(199
7) 4
93.
All available data onEx/A in central HIcollisions in the last20 years– Strong spread of the data points– Connected data points of the same measurement– Close to linear dependence on EIN
Experimental excitation energy
Experimental excitation energyAll available data onEx/A in central HIcollisions in the last20 years– Strong spread of the data points– Connected data points of the same measurement– Close to linear dependence on EIN
– Data within 35 % and 95 % of EAVAIL
Ex as a fraction of EAVAIL
– The same system for the central collisions and the same EIN displays different features
– The same system for the central collisions and the same EIN displays different features
– Different leading assumption used in various analysis
Ex as a fraction of EAVAIL
D. D
ore
et a
l. (I
ND
RA
Col
labo
rati
on),
Ph y
s. L
ett.
B49
1 (2
000)
15.Ar (95A MeV) + Ni INDRA experiment
analyzed in the 3 sources assumption
QP emission in BDCs
QP mass
QP excitation
experiment
3 sources analyses
Proton reduced rapidity distribution
Reaction dominantly of binary nature witha strong mid-rapidity contribution.
– The same system for the central collisions and the same EIN displays different features
– Different leading assumption used in various analysis
– Group data by the approach used
Ex as a fraction of EAVAIL
Neglected dynamical emission (?)
Pure kinematical considerations
Accounted dynamical emission
Added FOPI thermal energy
Summary “Hard” NN collisions play an importantNN collisions play an important role role in the dynamics of HIR already @@ EEFermiFermi
Maxima of excitationexcitation Ex (heat) gene- rated in a collision display linearitylinearity with incident energy EEININ
Ex represents a constant fraction ofconstant fraction of available system energy EEAVAILAVAIL
Some of experimental dataexperimental data (excluding the pre-equilibrium dynamical contribu- tion ?) display a tendency of similar similar constancyconstancy with EIN
Laboratory for Nuclear PhysicsLaboratory for Nuclear Physics Division of Experimental Physics Division of Experimental Physics RRuđeruđer Bošković Bošković Institute, Zagreb, CroatiaInstitute, Zagreb, Croatia
Zoran Basrak
11th International Conference on Nucleus-Nucleus Collisions May 28 – June 1st, 2011, San Antonio, TX–USA
Philippe Eudes, Maja Zorić, and François SébilleIn collaboration withIn collaboration with
Backup slides
Central collisions
30 fm/c = 1∙10-21 s
Ex≈EAVAIL
full stopping
Ein = 10A MeV
At EFermi (≈ 35A MeV)“hard” NN collisions
Ein = 35A MeV
129Xe + 120Sn
BDC > 95 % REAC
≈ 5 % σREAC
b = 3 fm ≈ 0.2 bmax
Ein = 50A MeV
Ein = 125A MeV
Mid-rapidity emission in BDCs
≈ pre-scission emissionMid-rapidity emission
max. compression
max. compression
local equilibration
local equilibration
Co
nfi
gu
rati
on
sp
ace
Imp
uls
e sp
ace
pre-scission post-scission
P. E
u des
, Z. B
asra
k an
d F
. Seb
i lle
, Ph y
s. R
ev. C
56 (
199 7
) 20
0 3.
Central collisions Above Coulomb barrier an adiabatic
system rearrangement with full stopping and full E dissipation; fusion process EDISSIP = EAVAIL
Increasing E: incomplete fusion EDISSIP < EAVAIL
From about the Fermi energy EFermi BDCBDC > 95 % REAC irrespectively of
- event centrality - system size - system asymmetry
Increasing contribution of hard NN collisions
F. H
adda
d e t
al . ,
Ph y
s. R
ev. C
60 (
199 9
) 03
1 603
.
Z dynam emiss
Z targ + Z proj
= 100
Dynamical emission component
Dem (%) =
SystemIncident
energy (MeV/u)
40Ar+27Al 41, 65
40Ar+107Ag 50, 75, 100
107Ag+40Ar 50
36Ar+58Ni 52, 74, 95
12OXe+129Sn 50, 75, 100
Excitation energy maxima
Eproj
Aproj
Eavail = Atarg Aproj
(Atarg+Aproj)2
Ex as a fraction of EAVAIL
– Fraction almost constantover a wide energy range
– For symmetric systemsbreak below EFermi
– Large variety of systems
Fraction for experimental Ex
Binary Dissipative Collisions (BDC)
– BDC opens around the Fermi energy
– σBDC > 95% σREAC
Irrespectively of - event centrality - system size - system mass
asymmetry
V.M
etiv
ier
et a
l . (I
ND
RA
Co l
labo
rat i
o n),
Nuc
l . P
hys.
A67
2 (2
000)
357
.
QP emission in BDCs
J. P
eter
et a
l ., N
u cl .
Ph y
s. A
593
(199
5) 9
5.
Reconstructed primary QP mass approxim. . equal to the projectile mass
Thus obtained primary QP extremely hot
Y. -
G. M
a et
al . ,
Ph y
s. L
ett .
B39
0 (1
997)
41.
Ar (95 MeV/u) Ni
Statistical emission component
Ph .
Eud
es a
nd Z
. Bas
rak,
Eu r
. Phy
s. J
. A 9
(20
00)
207.
Landau-Vlasov model simulationAr ( 65 MeV / u ) Al
The geniune primary QP emission
Ar (65 MeV/u) Al
D. Cussol et al., Nucl. Phys. A561 (1993) 298.
J. Peter et al., Nucl. Phys. A593 (1995) 95.
Heat & compression
– Maximal compression at ~25 fm/c
– In each volume cell a local equilibration at ~35 fm/c
– System scission at ~55 fm/c
Despite of the establishment of a local equi-librium throughout the compact system the (Eth/A)sys and (Ath/A)proj differ substantially:
Global equilibrium is far from being reached
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.
Head-on collisions
A universal linear proportionality law proves the eminent role of “hard” NN collisions.
A targ
(A targ + A proj ) 2Eavail =
c.m. E proj
A proj
A projDependence on available energy
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B62
5 (2
005)
26.
Dependence of relative sub-systems Eth/A on incident energy for head-on collisions
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.Projectile ratio =
(Eth/A)proj
Target ratio =
(Eth/A)sys
(Eth/A)targ
(Eth/A)sys
Ratio of thermal energy maxima
Dependence of relative sub-systems Eth/A on incident energy for head-on collisions
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.Projectile ratio =
(Eth/A)proj
Target ratio =
(Eth/A)sys
(Eth/A)targ
(Eth/A)sys
A symmetric system
Ratio of thermal energy maxima
Dependence of relative sub-systems Eth/A on incident energy for head-on collisions
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.Projectile ratio =
(Eth/A)proj
Target ratio =
(Eth/A)sys
(Eth/A)targ
(Eth/A)sys
An asymmetric system
Ratio of thermal energy maxima
Dependence of relative sub-systems Eth/A on incident energy for head-on collisions
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.Projectile ratio =
(Eth/A)proj
Target ratio =
(Eth/A)sys
(Eth/A)targ
(Eth/A)sys
Increasingly asymmetric systems
Ratio of thermal energy maxima
Dependence of relative sub-systems Eth/A on incident energy for head-on collisions
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.Projectile ratio =
(Eth/A)proj
Target ratio =
(Eth/A)sys
(Eth/A)targ
(Eth/A)sys
Ratio of thermal energy maxima
Dependence of relative sub-systems Eth/A on incident energy for head-on collisions
I. N
ovos
el e
t al . ,
Ph y
s. L
ett.
B6 2
5 (2
005)
26.
tal change from the fusion-deep inelastic into the BDC – partic.-spect,(fireball)-like behavior.
The reaction geo-metry is important in intermediate E HIC.
The Fermi energy is a transient region where the main reac-tion mechanism un-dergoes a fundamen-
Ratio of thermal energy maxima