pippo

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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

• Are we ready to do this?
• What do we need to improve?

It depends on the approximation we can accept
Michela D'Agostino
Bologna University
INFN-Bologna (Italy)
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Heavy Ion collisions
Freeze-out configuration
D E T E C T O R
Expansion
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124Sn 124Sn, E/A 50 MeV/A
b 6 fm
In event by event measurements statistical,
multidimensional analyses allow a centrality
sorting
D E T E C T O R
Freeze-out configuration
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H.I. collisions 1-st generation 4p devices

• Zi, ki, ?i, fi 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.

• mi are measured only for light products
• neutrons and ? are not detected

• The decaying system can be identified and its
  calorimetric excitation energy results from the
  energy balance

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Sorting the events multidimensional analysis
Chimera data
Peripheral collisions many sources
Central collisions one source
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1-st generation 4p devices stable beams
(V.Viola, R.Bougault-WCI-2005 TexasAM)

• 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.MeVWithin a phase-transition scenario,
  this value represents the transition energy.

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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)

Sequential feeding?
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Isotope analysis
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Symmetry energy and free nucleon densities
? 0.44 0.01 Symmetry Energy18-20 MeV
112,124Sn58,64Ni 35 AMeV central
collisionsCHIMERA-REVERSE Experiment
E. Geraci, et al., Nucl. Phys. A 732 (2004) 173,
Nucl .Phys. A734 (2004) 524
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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?
?(Z/A)²
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Experiments with n-rich/poor systems 32S58,64Ni
14.5 AMeV 3-IMF events
Observed 35 resonances, from He4 (dd) to Ne20
(aO16) 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 collaborationgarfield_at_LNL
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Level density (N,Z)
114,145Xe 40,48Ca Ebeam20-100 A.MeV e 3-7
A.MeV
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Resonance spectroscopy
t-a correlation function (Li7)
Position-sensitive hodoscope

• mmultiplicity, Nnumber of detectors
• e (m) e(1)m
• P(double)(m-1)/(2N)
• A reasonable compromise is P(double)lt5
• For m3 N10

Pochodzalla et al., PRC35 (1987)1695
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Why many-bodycorrelations?
?? 0.6o ? high granularity but in a limited
angular coverage not HR full identification
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Neck emission in semi-peripheral collisions
58Ni 112Sn at 35AMeV CHIMERA
PRELIMINARY
QT QP
MC with only statistical evaporation
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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

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Isospin effects strange chemical behaviour
for midvelocity particles
SnSn _at_ 38AMeV
THE HYDROGEN CASE
Preliminary
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
S.Piantelli et al. (in preparation)
TKEL
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Neck emission in semi-peripheral collisions
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Thermodynamics of finite systemsphase transition
Events sorted as a function of E (calorimetry)

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
• under the constraint of energy conservation
• Multics-Nucl.Phys.A699(2002)795

ltEkingt(3/2) ltm-1gtTlt?aAIMFgtT2
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Microcanonical heat capacity from fluctuations
The system being thermodynamically characterized
Ph.Chomaz , F.Gulminelli, NPA 647(1999) 153
Microcanonical fluctuations larger than the
canonical expectation? Then 1-st order phase
transition
Ckin/C 1-?2kin/?2can where ?2canT2CkinT2d
ltEkingt/dT
Multics-PLB473 (2000) 219NPA699 (2002)
795NPA734 (2004) 512 NPA749(2005) 55
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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
new analyses by Indra_at_GSI
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Average values and variances

• If we only use average and uncorrelated
  information on
• freeze-out multiplicity of neutrons, Z1,2 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!!!!!!

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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
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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,?,f of the Heavy residue (QPQT(?) for
  peripheral collisions)
• Z,A,E,?,f for fragments() and l.c.p. (high e)
• correlations among charged products
• () is it enough mass for Zlt20?
• At least on the average,
• for each reaction
• (sequential experiments)
• Neutron multiplicity energy
• (Gammas??)

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Heavy fragment masscharge identification
86Kr (25 MeV/u) 64Ni _at_MARS Recoil separator
Texas AM
Mass distribution of Ge (Z32) isotopes

G.A. Souliotis NN2003(Moscow)
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Future detector needs

• Z, A, and E (low energy thresholds)
• Granularity (for resonance spectroscopy)
• Neutron detection (En, Mn), at least on the
  average
• Cheap, flexible electronics
• Easy transportability
• Improvement of detector calibration (neural
  networks?)

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FAZIA Four p A-Z Indentification Array
half forward part

• 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

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FAZIA Four p A-Z Indentification Array