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