Transcript pippo

Eurisol and the nuclear EOS: experimental
challenges
Keyword from the 2003 Eurisol report:
Isospin
 Level density parameter dependence on (N,Z)
 Liquid gas phase transition
 Isospin effects and symmetry term of the EOS
 Isospin effects in semi-peripheral Heavy-Ion
reactions: symmetry term of the EOS
Thermodynamics
of a single source
Dynamics of
many-sources
1. Are we ready to do this?
It depends on the approximation we
2. What do we need to improve? can accept
Michela D'Agostino
Bologna University
INFN-Bologna (Italy)
Heavy Ion collisions
Freeze-out
configuration
D
E
T
E
C
T
O
R
γ emission
Expansion
~20 fm/c
(10-22 sec)
~100 fm/c
~100÷1000 fm/c
Vacuum
(10-6 mb)
~1014 fm/c
124Sn+ 124Sn, E/A = 50 MeV/A
80 fm/c
(2.4x10-22 sec)
180 fm/c
(5.4x10-22 sec)
Freeze-out
configuration
b = 6 fm
In event by event measurements
statistical, multidimensional analyses
allow a centrality sorting
~÷1000 fm/c
Secondary decays
~1014 fm/c
D
E
T
E
C
T
O
R
H.I. collisions: 1-st generation 4π devices
•Zi, ki, θi, φi are measured for almost all
charged products, event by event, with
high energy resolution (few %) and low
energy thresholds (gas detectors)
•Fragments and particles are detected
at ~1014 fm/c, as they were at 103 fm/c,
since the propagation in vacuum does not
allow further interactions with matter.
•Statistical multidimensional analyses
performed on global (event) observables
allow to sort the events in classes of
centrality.
•The decaying system can be identified and
its calorimetric excitation energy results
from the energy balance:
M
E * m0   ( mi  ki )  M n mn  kn 
i 1
•mi are measured only for
light products
•neutrons and γ are not
detected
Sorting the events: multidimensional analysis
124Sn+
64Ni
Filtered CMD
model
35MeV/A
Peripheral
collisions:
A
many sources
Vbeam
Chimera
data
Z
Z,A for
light Ions
Central collisions
25 AMeV
35 AMeV
Au+C
Au+Cu Au+Cu Au+Au
E. Geraci
et al.,NPA732(2004)173,NPA734
(2004)524
Z>8 open circles
>18Central
full points
collisions:
>28
open squares
>38
squares
onefull
source
>48 open triangles
>58 full triangles
M
>68 open (crosses
k ) (k )
(k )
*=1.5
*=3
Tij   pi p j w (i,j  1,3 )
k 1
MulticsNPA734(2004)487
Multics-NPA724 (2003) 329
*=4.5
*=7 A.MeV
1-st generation 4π devices & stable beams
(V.Viola, R.Bougault-WCI-2005 TexasA&M) Central collisions
• The current state of nuclear
calorimetry permits determination
of the E*/A of the fragmenting
source to an accuracy of about 20%.
Nearly all experiments can be made
self-consistent within this range
Z-2.1
• For all multifragmentation
experiments, the region in which
there is a dramatic change in
reaction observables corresponds
to E*/A = 5 +/-1 A.MeV
Within a phase-transition scenario, Multics: Central from Z0=85 to Z0=100
this value represents the transition (lines)
Multics: Au peripheral Z0=79 (symbols)
energy.
Isis: π+Au 8 GeV/c NPA734(2004)487
Fasa: p,α+Au
4-14 GeV NPA709(2002)392
Multics-NPA724 (2003) 329
Temperature and caloric curve
For the caloric curve one needs to measure:
• Heavy residue (or QP)
• Slopes of 1-st chance l.c.p. energy spectra
• Isotopes (for double ratios)
J. Pochodzalla et al, PRL 75, 1040 (1995)
Sequential feeding?
R. Wada et al., PRC 39, 497 (1989)
N.Le Neindre et al , NIM A490 (2002) 251
Isotope analysis
T from double ratios: Y(He3)/Y(He4)
Y(Li6)/Y(Li7)
V1=V2
Isobaric ratio (for mirror nuclei) :
Y(N1 , Z1 )  n B T

e
Y ( N2 ,Z 2 )  p
Symmetry energy and free nucleon densities
Isotopicratio :
Y124 Sn 64 Ni ( N , Z )
R21( N , Z ) 
 eN  Z
Y112 Sn 58 Ni ( N , Z )
Csym 
 = 0.44 ± 0.01
T
2
2
Z Z
   
 A 1  A  2
Symmetry Energy~18-20 MeV
Isobaric ratio (for mirror nuclei) :
Y(N1 , Z1 )  n B T

e
Y ( N2 ,Z 2 )  p
112,124Sn+58,64Ni
35 AMeV central collisions
CHIMERA-REVERSE Experiment
E. Geraci, et al., Nucl. Phys. A 732 (2004) 173, Nucl .Phys. A734 (2004) 524
Extraction of symmetry energy
Asy-soft
Asy-stiff
D.Shetty et al., P. R.C 70 (2004) 011601
E.Geraci et al.,NPA732(2004)
A.Botvina et al., PRC65(2002):
Sequential feeding?
Δ(Z/A)²
Experiments with n-rich/poor systems
32S+58,64Ni 14.5 AMeV 3-IMF events
Observed 35 resonances, from He4 (d+d) to Ne20 (a+O16)
A rough calculation of “feeding correction” through correlation
functions suggests an increase of T by 0.5 MeV for few % of decrease
in the He4 yield
Before drawing conclusions
on temperature, densities:
Isotope emission time
scales have to be checked
through correlation
functions
nucl-ex collaboration&garfield@LNL
Level density (N,Z)
J.B. Natowitz et al., PRC 65, 034618 (2002)
J.Besprosvany Al-Quraishi
and S.Levit PRC63,065803(2001)
- PLB 217 (1989)
1
N=Z
114,145Xe
+
40,48Ca
Ebeam=20-100 A.MeV ε*= 3-7 A.MeV
Resonance spectroscopy
t-α correlation function (Li7*)
m=multiplicity, N=number of detectors
•ε (m) = ε(1)m
•P(double)=(m-1)/(2N)
Pochodzalla et al., PRC35 (1987)1695
A reasonable compromise is P(double)<5%
For m=3 N=10
Why many-body
correlations?
α-particles
R.J. Charity et al., PRC63 024611
60Ni+100Mo
11 A.MeV
Δθ≈ 0.6o  high granularity
but in a limited angular coverage
& not HR full identification
α-α
Neck emission in semi-peripheral collisions
58Ni
QT
+ 112Sn at 35AMeV CHIMERA
QP
filtered
Midvelocity Emissions: which origin?
S.Piantelli et al. Phys.Rev.Lett.88(2002),052701
A.Mangiarotti et al. Phys.Rev.Lett93(2004)232701
-Midvelocity LCP and fragments seem to be compatible with two sources, one
“prompt”, the other like a “surface component”. This can be the evolution of
the fast oriented fission for the most asymmetric splits
See: Di Toro et al. Prog.Part.Nucl.Phys 53(2004),81 -- A.Chernomoretz et al. PRC 65(2002)054613
Isospin effects: strange ‘chemical’ behaviour
for midvelocity particles
Sn+Sn @ 38AMeV
THE HYDROGEN CASE
Only deuterons N/Z=1
For Midvel emission we
have a large neutron
enrichment.
Multifragmentation?
Isospin Distillation?
N/Z
Statistical
Evaporation
-N/Z for
hydrogen is in
good agreement
with statistical
codes
Only protons N/Z=0
TKEL
S.Piantelli et al.
(in preparation)
Neck emission in semi-peripheral collisions
Thermodynamics of finite systems:
phase transition
Events sorted as a function of E* (calorimetry)
M
E * m0   ( mi  ki )  M n mn  kn 
i 1
E*= Econfig
+ Ekin
E*= Ecoul(V)+Qv+ Eint(T)+Etr(T)
We can back-trace from data
•the average volume of the system (Coulomb trajectories)
•the temperature T
<Ekin>=(3/2) <m-1>T+<aAIMF>T2
under the constraint of energy conservation
Multics-Nucl.Phys.A699(2002)795
Microcanonical heat capacity from fluctuations
The system being thermodynamically characterized:
Ph.Chomaz , F.Gulminelli, NPA 647(1999) 153
Ckin/C = 1-2kin/2can
where:
2can=T2Ckin=T2d<Ekin>/dT
Microcanonical
fluctuations
larger than the canonical
expectation? Then
1-st order phase transition
Multics-PLB473 (2000) 219;NPA699 (2002) 795;NPA734 (2004) 512; NPA749(2005) 55
Heat capacity from fluctuations
Multics:
PLB473 (2000) 219
NPA699 (2002) 795
NPA734 (2004) 512
NPA749(2005) 55
E*/A0(AMeV)
Grey area: peripheral collisions
Points: central collisions:
Au+C
Au+Cu
Au+Au
+ new analyses by
Indra@GSI
Indra: NPA699(2002)795
Average values and variances
SMM events
Nucl.Phys.A699(2002)795
If we only use average and
uncorrelated information
on:
•freeze-out multiplicity of
neutrons, Z=1,2 and IMFs
•sequential feeding
•excitation energy of
primary fragments
•N/Z of final products
We see that one half of the
game is played by missing
correlations!!!!!!
3-d Spinodal
region
Instability growth time
100 fm/c (dashed/orange)
50 fm/c (dotted/red)
M.Colonna et al. PRL 88(2002) 122701
More asymmetric systems are less unstable
Do we need to improve the detection for the
“isospin” physics?
For all the measured reactions (high geometrical coverage,
high energy resolution), event by event :
•Z,A,E,θ,φ of the Heavy residue (QP&QT(?) for peripheral
collisions)
•Z,A,E,θ,φ for fragments(*) and l.c.p. (high ε*)
•correlations among charged products
(*) is it enough mass for Z<=20?
At least on the average,
for each reaction
(sequential experiments)
•Neutron multiplicity & energy
•(Gammas??)
Heavy fragment mass&charge identification
86Kr (25
MeV/u) + 64Ni @MARS Recoil separator Texas A&M
Mass distribution of Ge (Z=32) isotopes
G.A. Souliotis NN2003(Moscow)
Future detector needs
Chimera: Pulse shape gives Z identification
with ~ 4 MeV/A energy threshold for particles
stopped in Si detector
1. Z, A, and E (low energy thresholds)
2. Granularity (for resonance
spectroscopy)
3. Neutron detection (En, Mn), at least on
the average
4. Cheap, flexible electronics
5. Easy transportability
6. Improvement of detector calibration
(neural networks?)
Nuclex: Reverse mounting of the Si detector &
Digital Pulse Shape give Z identification with ~
2.5 MeV/A energy threshold for particles
stopped in Si detector
FAZIA: Four π A-Z Indentification Array
• ~6000 telescopes: Si-ntd/Si-ntd/CsI
• possibility of coupling with other detectors like spectrometer, gas chamber,
neutron detectors
• ~1000 hits/s
• maximum multiplicity ~150/event
• complete Z identification and A up to ~30
• digital electronics for pulse-shape discrimination
FAZIA: Four π A-Z Indentification Array