M. Valentina Ricciardi GSI Darmstadt, Germany

1. Fragmentation Reactions: Recent Achievements and Future Perspective M. Valentina Ricciardi GSI Darmstadt, Germany New London, June 15-20, 2008

2. 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 motivationsto study fragmentation. III. How is the future of fragmentation?

3. High-energy nucleus-nucleus reactions deep-inelastic transfer fragmentation / spallation multifragmentation vaporisation (fireball) impact parameter P R O D U C T I O N O F R I B s incomplete fusion multifragmentation multifragmentation 40 A MeV 1 A GeV impinging energy

4. thermalisation cold fragment de-excitation collision 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

5. 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)

6. Main features of fragmentation reactions Mass yields – dependence on available energy asymptotic behavior

7. Main features of fragmentation reactions N/Z of the final fragments evaporation attractor line R. J. Charity, PRC 58 (1998) asymptotic behavior

8. 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

9. Previous understanding of fragmentation reactions Asymptotic behaviors: in mass distributions in N/Z (attractor line) The idea behind limiting fragmentationand in the semi-empirical codeEPAX (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?

10. 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)

11. ISOSCALING (dedicated talks) Beautiful data Very precise production cross-sections on the entire production range 58,64Ni on Be at 140 A MeV M. Mocko et al., Phys. Rev. C 74 (2006) 054612 136,124Xe on Pb at 1 A GeV D. Henzlova, submitted to PRC

12. 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

13. Memory of the past  1 A GeV 238U on Pb  1 A GeV 238U on Ti K.-H. Schmidt et al., NPA 710 (2002) 157 D. Henzlova et al., submitted to PRC cold residues preserve memory on the initial N/Z over the whole nuclear charge range evaporation corridor not reached

14. 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

15. Footprints of a superfluid A25 T/MeV gas 5 coexistence liquid Nuclear superfluidity: it vanishes at about E*~10 MeV  valid only for low-energy-reaction residues 0.5 superfluid E/MeV 10 70 300

16. Footprints of a superfluid 5500 MeV protons on 238U A. M. Poskanzeret al., Phys. Rev. C 3 (1971) 882 C. N. Knottet al., Phys. Rev. C 53 (1996) 347 C. Zeitlin et al., PRC 77 (2008) 034605 +protons

17. 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 fragmentsgamma emission becomes competitive to particle decay Yields from highly excited nuclei reflect the transition from liquid to superfluid ● N=Z■ N=Z+2 ▲N=Z+4 N=Z+6 ● N=Z+1■ N=Z+3▲ N=Z+5 1 AGeV 238U Ti M. V. Ricciardi, Nucl. Phys. A 733 (2004) 299

18. Measuring neutron separation energies far from stability W. A. Friedmann, M. B. Tsang, PRC 67 (2003) two-step scheme (dedicated talk) 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

19. 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)

20. Theoretical prediction: "Spectator response to the participant blast"L. Shi, P. Danielewicz, R. LaceyPhys. Rev. C 64 (2001) 034601 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

21. Mean longitudinal velocity M. Notani et al., PRC 76 (2007) 044605 V. Henzl, PhD thesis, University of Prague, 2006

22. 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

23. 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

24. Future perspectives

25. Future perspectives Measure: A, Z Fission fragments n, p, gammas velocity R3B @FAIR - Germany Exclusive experiments AND high resolution

26. 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