M' Valentina Ricciardi

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M. Valentina Ricciardi GSI Darmstadt, Germany
New London, June 15-20, 2008
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Motivation and Outlook
I. Recall old results and features of
fragmentation reactions Initial motivations
Radioactive-ion-beams production
Astrophysics Many data were measured in the
last decades the major features of
fragmentation products were determined in the
past II. Recent achievements How recent
experimental results confirm (or not) the
validity of our picture How recent results
can be exploited for fundamental physics or
applications Recent results brought new
important motivations to study fragmentation. II
I. How is the future of fragmentation?
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High-energy nucleus-nucleus reactions
fragmentation / spallation multifragmentation
vaporisation
(fireball)
deep-inelastic transfer
impact parameter
P R O D U C T I O N O F R I B s
incomplete fusion multifragmentation multifragme
ntation
40 A MeV
1 A GeV
impinging energy
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Understanding of fragmentation reactions
Collision removal of nucleons in quasi-free
nucleon-nucleon collisions. Thermalisation
formation of a compound nucleus Deexcitation
Highly excited fragments loose additional mass
and cool down. Cold residual nucleus Gamma
decay and structural effects came into the game
fast slow
Experimental observables indicate the existence
of these sequential stages

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Fragmentation reactions
197Au 197Au at 1 A GeV
Z of the 2nd heaviest fragment
Z of the heaviest fragment
Data Courtesy of ALADIN, GSI
197Au 197Au at 1 A GeV V. Henzl, PhD Thesis
(Univ. Prague, Czech Republic, 2006)
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Main features of fragmentation reactions
Mass yields dependence on available energy
asymptotic behavior
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Main features of fragmentation reactions
N/Z of the final fragments
evaporation attractor line
R. J. Charity, PRC 58 (1998)
asymptotic behavior
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Main features of fragmentation reactions
Kinematical features
D. E. Greiner et al., PRL 35 (1975) 152
D. J. Morrissey, Phys. Rev. C 39 (1989) 460
2.1 A GeV 12C Be
Morrissey's systematic
10Be
systematic behavior
R. Pfaff et al., Phys. Rev. C 51 (1995) 1348
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Previous understanding of fragmentation reactions
Asymptotic behaviors in mass distributions in
N/Z (attractor line)
The idea behind limiting fragmentation and
in the semi-empirical code EPAX
(K. Sümmerer and B. Blank, PRC 61 (2000) 034607
NIM B 204 (2003) 278 )
Systematics in kinematics (D. J. Morrissey,
Phys. Rev. C 39 (1989) 460)
J. Hüfner, Phys. Reports 125, 1985 "Can we expect
a simple description of a complicated process
like fragmentation? I think yes. A simple
description works because the process is
extremely complicated and phase space dominates
over dynamics."
Can we confirm this nowadays?
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What did come up in the last years? Use of high
resolution magnetic spectrometers - Full
isotopic identification of the reaction residues
over the whole mass range - High precision
velocity measurements MARS recoil separator at
Texas AM University (Fermi energies) A1900
fragment separator at MSU, East Lansing (above
Fermi energies) FRS magnetic spectrometer at GSI,
Darmstadt (relativistic energies)
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Beautiful data
Very precise production cross-sections on the
entire production range
136,124Xe on Pb at 1 A GeV D. Henzlova, submitted
to PRC
58,64Ni on Be at 140 A MeV M. Mocko et al., Phys.
Rev. C 74 (2006) 054612
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Memory of the past
J. Reinhold et al., PRC 58 (1998) 247
Westfall (1979), Porile (1964), Ku (1977),
R. Pfaff et al., PRC 53 (1996) 1753 78Kr on Ni
at 75 A MeV
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Memory of the past
? 1 A GeV 238U on Pb ? 1 A GeV 238U on Ti
D. Henzlova et al., submitted to PRC
K.-H. Schmidt et al., NPA 710 (2002) 157
cold residues preserve memory on the initial N/Z
over the whole nuclear charge range
evaporation corridor not reached
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Isospin thermometer
The "memory effect" can be explained if break-up
is included The temperature can be measured by
tracing back evaporation
K.-H. Schmidt et al., NPA 710 (2002) 157
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Footprints of a superfluid
A?25
T/MeV
gas
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coexistence
liquid
Nuclear superfluidity
it vanishes at about E10 MeV
? valid only for
low-energy-reaction residues
0.5
superfluid
E/MeV
70
10
300
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Footprints of a superfluid
5500 MeV protons on 238U
A. M. Poskanzer et al., Phys. Rev. C 3 (1971)
882
C. N. Knott et al., Phys. Rev. C 53 (1996) 347
C. Zeitlin et al., PRC 77 (2008) 034605
protons
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Footprints of a superfluid
Even-odd fluctuations are produced at the end of
the evaporation cascade ? Structural effects are
restored in the end products of hot decaying
nuclei (transition from normal liquid to
superfluid) ? For heavy fragments gamma emission
becomes competitive to particle decay Yields
from highly excited nuclei reflect the transition
from liquid to superfluid
? NZ NZ2 ?NZ4 ?NZ6 ? NZ1
NZ3 ? NZ5
1 A?GeV 238U ? Ti
M. V. Ricciardi, Nucl. Phys. A 733 (2004) 299
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Exploiting the large statistical fluctuations in
N/Z
cold fragmentation
Radioactive Ion Beams
A. Stolz et al., PRC 65 (2002) 064603
M. De Jong et al., NPA 628 (1998) 479
K.H. Schmidt et al., NPA 542 (1992) 699
J. Benlliure et al., NPA 660 (1999) 87
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Exploiting the production cross sections of
n-rich nuclei
determination of nuclear binding energies
exponential dependence
Mocko et al., EPL 79 (2007) 12001 M.
B. Tsang et al., Phys. Rev. C 76, 067601 (2007)
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Mean longitudinal velocity
Morrissey systematic indicates - a "slowing
down" for small mass losses, attributed to
friction - a chaotic behavior for large
mass-losses
Morrissey systematics
Experimental evidence of the effects of the
participants on the spectators
D. J. Morrissey, Phys. Rev. C 39 (1989) 460
M. V. Ricciardi et al., PRL 90 (2003) 212302
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Mean longitudinal velocity
M. Notani et al., PRC 76 (2007) 044605
V. Henzl, PhD thesis, University of Prague, 2006
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Mean longitudinal velocity
Friction in abrasion can we learn something
about in-medium nucleon-nucleon cross sections?
work in progress !
A. Bacquias, PhD thesis, University of
Strasbourg, 2008
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Longitudinal momentum width
analytical formula
Morrissey
The effects of abrasion break-up
coulomb expansion evaporation are considered
A. Bacquias, PhD thesis, University of
Strasbourg, 2008
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Future perspectives
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Future perspectives
Measure A, Z Fission fragments n, p,
gammas velocity
R3B _at_FAIR - Germany Exclusive experiments AND
high resolution
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Conclusion and Discussion
Accurate and extensive data show that systematic
and asymptotic behaviors are not respected Our
understanding of the fragmentation process had to
be revisited Three different phases can be
accessed by fragmentation reactions Dynamical
effects (in the collision?) are visible Important
fundamental physical issues can be studied with
fragmentation reactions Fragmentation reactions
a path through phase-transitions where dynamical
effects are important