Nuclear Structure at Extreme conditions through γ spectroscopy measurements

Transcription

1 Silvia Leoni Nuclear Structure at Extreme conditions through γ spectroscopy measurements New Challenges in Nuclear Structures : Nuclei at High Spins Nuclei at High Temperature Exotic Nuclei Milano University and INFN Milano A.Bracco, G.Benzoni, N.Blasi, F.Camera, S.Leoni, B.Million, M.Pignanelli,O.Wieland

2 The Hierarchy of Matter Interdiciplinary research Particle physics & astrophysics Nucleus: m E 10 6 ev Accelerators Large Laboratories Large Collaborations

3 Frontiers of Nuclear Structures: Exotic Nuclei Proton Proton Rich proton radioactivity proton neutron pairing Nucleosynthesis (rp process) Fe rp-process neutron drip-line SuperHeavy Limit of Atomic Number (Z=112,114,116) proton drip-line r-process Terra Incognita Neutron Rich Nuclear synthesis in Supernovae Neutron n halos n skins Nucleosynthesis (r process)

4 pygmy resonances vibration of neutron excess against inert core of equal n and p Relative Abundance Astrophysical implications r-process exp Theory +pygmy A S. Goriely, Phys. Lett. B 436 (1998) 10 The properties of nuclei have great impact on the entire universe

5 FAR from Stability Development of Radioactive Beams Facilities USA: RIA EUROPE: EURISOL JAPAN: RIKEN Ganil Cern LNL GSI LNS INFN Laboratori Nazionali Legnaro Study for the production of exotic species

6 Integrated Infrastructure Initiative of the European nuclear structure research 27 countries 45 institutions Networks: MANET, CARINA, GAMMAPOOL, EWON, NuPECC, PANSI3, SHE, TNET Laboratory Access: GSI, UCL-CRC, GANIL, JYU-JYFL, INFN-LNL, ECT*, RUG-KVI, CERN-ISOLDE Joint Research Activities: ACTAR, AGATA, Charge Breeding, DLEP, EXL, INTAG, ISIBHI, LASER, RHIB, SAFERIB, TRANSPEC

7 Nuclear Structure Experimental Study Nuclear Reactions 5 MeV/A 400 MeV/A projectile target n α γ v/c 1-50 % p γ Coulomb Excitation Transfer Reactions Fusion reactions Reaction cross sections Spins, masses γ and particle decay

8 Heavy Ions Fusion reactions Nuclei at High Spins: Nuclear superfluidity Highly deformed shapes

9 Heavy Ions Fusion Reactions: population of high spins states (> 40 h) Angular momentum limits (before fission) compound nucleus formation sec L max RIB 10h stable sec Yb A 10-9 sec ground state rotations/sec I

10 3 6 γ-ray patterns reveal nuclear structure γ detector t 10-8 sec 1 5 E γ sec 4 E γ2 2 Collective rotation leads to regular band structures Single-particle generation of spin leads to an irregular level structure

11 Present Arrays Future Arrays Large Gamma Arrays based on Compton Suppressed Spectrometers Tracking Arrays based on Position Sensitive Ge Detectors EUROBALL ε 10 5 % ( M γ =1 M γ =30) AGATA ε % ( M γ =1 M γ =30) Cost 40 M

12 POSTER: Future developments in γ-ray spectroscopy: the European project AGATA F. Crespi, G. Benzoni, A. Bracco, S. Brambilla, N. Blasi, F. Camera, A. Geraci, S. Leoni, B. Million, M. Pignanelli, G. Ripamonti, E. Vigezzi, O. Wieland and the AGATA collaboration

13 174 Hf γ-ray patterns reveal nuclear structure E γ E γ [kev] 2 h E ( I ) = I ( I + 1) 2 I 2 h E γ ( I ) = 4 I 2 I 2 4 h E γ = constant I spacing I Collective rotation leads to regular band structures Single-particle generation of spin leads to an irregular level structure

14 The nucleus is NOT a rigid body is NOT a irrotational fluid I rigid Back-bending I [2/h 2 MeV -1 ] I exp I fluid I I= I 0 +kω A The nuclear force is short range phase transition superfluid normal intense forces only between close nucleons Nuclear superfluidity nucleons form Cooper pairs (binding energy )

15 Stringent test of Shell structure and Strong effective force Superdeformed and Hyperdeformed shapes fission nucleons are organized in shells magic numbers are found when shells are filled harmonic oscillator :2 2:1 3:1 New magic numbers: SuperDef nuclei (2:1) HyperDef nuclei (3:1) 4 2 Potential energy I=50 I=40 I=30 Deformation ε

16 Understanding of shell structure: Observation of highly deformed shapes Population mechanisms Decay mechanisms 152 Dy SD band Present Status: 200 Super-Def bands known A = 80, 130, 150, 190 P.Twin et al. Phys. Rev. Lett. 57(1986)811

17 Population of super deformed bands Feeding from Giant Dipole Resonance GDR intensity (%) NORMAL deformed γ γ SUPER deformed 15 MeV 9 MeV enhanced SD intensity at high spins Relative Intensity 143 Eu EUROBALL DATA relative intensity Eu - Euroball D ata SD Yrast Ridge Bump Triaxial Sperical SD structures f GDR (SD)/f GDR (N D) ND structures E γ [MeV] E γ [MeV] G. Benzoni et al., PLB540(2002)199 Spin

18 POSTER: Nuclear structure at finite temperature probed by the giant dipole resonance G. Benzoni, O. Wieland, A. Bracco, N. Blasi, F. Camera, F. Crespi, S. Leoni, B. Million

19 Decay-out of super deformed bands Tunneling process through potential barriers SD band ND minimum SD minimum Rigid body Super deformed band the tunneling is governed by the inertial mass of the nucleus M superfluid L m SD 50% ND 136 Nd Perries et al., PRC60(1999) phase transition normal superfluid system

20 Heavy Ions Fusion reactions Nuclei at High Spins: Nuclear superfluidity Highly deformed shapes Nuclei at High Temperature: transition order to chaos

21 Order-to-chaos transition n CN γ Compound Nucleus CHAOS Γ rot I-2 I I+2 ONSET of CHAOS T 0 I-2 I I+2 Regular Bands ORDER

22 Lise Meitner Prize for Nuclear Science year 2004 B.Herskind & P.Twin 168 Yb VALLEY (Chaos) RIDGES (Order) Degree of Chaoticity 1.5 CHAOS ORDER Internal Energy [MeV] Analysis of quasi-continuum γ γ coincidence spectra A.Bracco and S.Leoni, Rep.Prog.Phys. 65 (2002) 299 the nucleus becomes chaotic at U 2.5 MeV S. Leoni et al., PRL93(2004) G. Benzoni et al., PLB615(2005)160

23 Heavy Ions Fusion reactions Nuclei at High Spins: Nuclear superfluidity Highly deformed shapes Nuclei at High Temperature: transition order to chaos Transfer Reactions Towards the N-dripline: light N-rich nuclei

24 Limits of Nuclear Existence Proton proton drip-line neutron drip-line Stringent Test of Shell Model Neutron Milano project Study of neutron-rich N=12-16 F,O,Ne isotopes

25 Search for the n-dripline test of shell model deep-inelastic & multi-nucleon transfer reaction Milano Proposal at LNL/GANIL(Francia) Associate European Laboratory C B Be Li He H O N Mg Na Ne F 24 O 31 F 23 O 24 O RIKEN 31 F MSU 24 O location of n drip line between F and O is not understood: N=16 for O and N=22 for F M.Fauerbach et al., PRC53 (1996) 647 H.Sakurai et al., PLB448 (1999) 180

26 Laboratori Nazionali di Legnaro + European Coll. PRISMA spectrometer CLARA 25 Euroball Ge Det. Efficiency ~ 3 % A & Z identification in-beam γ-ray

27 POSTER: Spectroscopy of 120 Sn homologous levels via the high resolution 123 Sb (ppol,alpha) 120 Sn reaction P. Guazzoni, L. Zetta, A. Covello, A. Gargano, G. Graw, R. Hertenberger, H.F. Wirth, B. Bayman, M. Jaskola POSTER: Digital pulse shape acquisition from the telescopes of CHIMERA AZ-4pi detector P. Guazzoni, S. Russo, M. Sassi, L. Zetta

28 Summary Development of Accelerators (RIB) and Detection Systems: limits of nuclear existence (p and n driplines) information on phase transitions in nuclear matter (superfuidity, order and chaos) study the different excitation modes of the nucleus (rotations & vibrations) Understanding of Shell structure & Strong effective force FAR from STABILITY

29 Collaboration Università degli Studi and INFN sezione di Milano, ITALY LNL, Laboratori Nazionali di Legnaro, ITALY Università and INFN sezione di Padova, ITALY Università di Camerino and INFN Perugia, ITALY INFN sezione di Genova, ITALY Institut de Physique Nucleaire, Orsay, FRANCE IRES, Strasbourg, FRANCE GANIL, Caen, FRANCE IPN, Lyon, FRANCE GSI, Darmstadt, GERMANY KOLN University, GERMANY NBI, Copenhagen, DENMARK LUND University, Lund, SWEDEN The Niewodniczanski Institute, Krakow, POLAND CERN, Geneve, SWITZERLAND Daresbury Lab, UK Liverpool University, UK Manchester University, UK