M. Valentina Ricciardi
GSI Darmstadt, Germany
New London, June 15-20, 2008
Fragmentation Reactions:Recent Achievements and Future Perspective
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.
III. How is the future of fragmentation?
imp
act
par
amet
er
fragmentation / spallation
multifragmentation
vaporisation (fireball)
deep-inelastic transfer
incomplete fusion multifragmentation
multifragmentation
High-energy nucleus-nucleus reactions
impinging energy
P R O D U C T I O N O F R I B s
40 A MeV 1 A GeV
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
Experimental observables indicate the existence of these sequential stages
fast slow
de-excitation
cold fragment
thermalisation
collision
Understanding of fragmentation reactions
Fragmentation reactions
Data: Courtesy of ALADIN, GSI
Z o
f th
e 2nd
hea
vies
t fr
agm
ent
197Au + 197Au at 1 A GeV
V. Henzl, PhD Thesis (Univ. Prague, Czech Republic, 2006)
Z of the heaviest fragment
197Au + 197Au at 1 A GeV
Main features of fragmentation reactions
Mass yields – dependence on available energy
asymptotic behavior
asymptotic behavior
evaporation attractor line
N/Z of the final fragments
Main features of fragmentation reactions
R. J. Charity, PRC 58 (1998)
systematic behavior
D. J. Morrissey, Phys. Rev. C 39 (1989) 460
Kinematical features
Main features of fragmentation reactions
D. E. Greiner et al., PRL 35 (1975) 152
10Be
2.1 A GeV 12C + Be
R. Pfaff et al., Phys. Rev. C 51 (1995) 1348
Morrissey's systematic
Previous understanding of fragmentation reactions
Asymptotic behaviors:
in mass distributions
in N/Z (attractor line)
Systematics in kinematics (D. J. Morrissey, Phys. Rev. C 39 (1989) 460)
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 )
Can we confirm this nowadays?
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."
Recent achievements
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 A&M University (Fermi energies)
A1900 fragment separator at MSU, East Lansing (above Fermi energies)
FRS magnetic spectrometer at GSI, Darmstadt (relativistic energies)
Very precise production cross-sections on the entire production range
Beautiful data
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
ISOSCALING (dedicated talks)
Memory of the past
Westfall (1979), Porile (1964), Ku (1977),
J. Reinhold et al., PRC 58 (1998) 247
R. Pfaff et al., PRC 53 (1996) 1753
78Kr on Ni at 75 A MeV
evaporation corridor not reached
D. Henzlova et al., submitted to PRC
Memory of the past
cold residues preserve memory on the initial N/Z over the whole nuclear charge range
1 A GeV 238U on Pb
1 A GeV 238U on Ti
K.-H. Schmidt et al., NPA 710 (2002) 157
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
superfluid
liquid
coexistence
gas
E/MeV
5
7010 300
A25
0.5
T/MeV
Nuclear superfluidity: it vanishes at about E*~10 MeV valid only for low-energy-reaction residues
Footprints of a superfluid
A. M. Poskanzer et al., Phys. Rev. C 3 (1971) 882
C. N. Knott et al., Phys. Rev. C 53 (1996) 347
5500 MeV protons on 238U
+ protons
Footprints of a superfluid
C. Zeitlin et al., PRC 77 (2008) 034605
Footprints of a superfluid
1 AGeV 238U Ti
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
M. V. Ricciardi, Nucl. Phys. A 733 (2004) 299
● N=Z ■ N=Z+2 ▲N=Z+4 N=Z+6
● N=Z+1 ■ N=Z+3 ▲ N=Z+5
cold fragmentation
A. Stolz et al., PRC 65 (2002) 064603
J. Benlliure et al., NPA 660 (1999) 87
M. De Jong et al., NPA 628 (1998) 479
K.H. Schmidt et al.,
NPA 542 (1992) 699
Exploiting the large statistical fluctuations in N/Z
two-step scheme (dedicated talk)
Radioactive Ion Beams
Measuring neutron separation energies far from stability W. A. Friedmann, M. B. Tsang,
PRC 67 (2003)
Exploiting the production cross sections of n-rich nuclei
Mocko et al., EPL 79 (2007) 12001 M. B. Tsang et al., Phys. Rev. C 76, 067601 (2007)
exponential dependencedetermination of nuclear binding energies
Morrissey systematic indicates:
- a "slowing down" for small mass losses, attributed to friction
- a chaotic behavior for large mass-losses
Mean longitudinal velocity
Morrissey systematicsD. J. Morrissey, Phys. Rev. C 39 (1989) 460
Experimental evidence of the effects of the participants on the spectators
M. V. Ricciardi et al., PRL 90 (2003) 212302
Theoretical prediction: "Spectator response to the participant blast"L. Shi, P. Danielewicz, R. LaceyPhys. Rev. C 64 (2001) 034601
V. Henzl, PhD thesis, University of Prague, 2006
Mean longitudinal velocity
M. Notani et al., PRC 76 (2007) 044605
Mean longitudinal velocity
A. Bacquias, PhD thesis, University of Strasbourg, 2008
Friction in abrasion: can we learn something about in-medium nucleon-nucleon cross sections?
work in progress !
Longitudinal momentum width
A. Bacquias, PhD thesis, University of Strasbourg, 2008
Morrisseyanalytical formula
The effects of
abrasion + break-up + coulomb expansion + evaporation
are considered
Future perspectives
Future perspectives
Measure:
A, Z
Fission fragments
n, p, gammas
velocity
R3B @FAIR - Germany
Exclusive experiments AND high resolution
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
Conclusion and Discussion