1. 13-15 October 2008 LNS – INFN Catania LEA COLLIGA Collective Modes of Excitation Silvia Leoni Università di Milano INFN – Sezione di Milano Vibrations & Rotations  -spectroscopy in the continuum Physics Cases with Stable & Radioactive Beams

2. Collective Rotation o Order-to-Chaos Transition in Warm Nuclei High-K high spin states [fusion evaporation and deep-inelastic] Collective Vibrations o HOT Giant Resonances 1. Dynamic Dipole emission in pre-equilibrium reaction 2. Giant Dipole Resonance: Isospin Mixing at T  0 [fusion evaporation 5-10 MeV/A] o Highly excited low spin states Pygmy states (up to GDR and GQR region) [inelastic scattering with heavy-ions  10MeV/A] Present campaigns and LOI’s AGATA Demonstrator@LNL and SPIRAL2 …

3. Dipole Resonance Emission from HOT nuclei t=0 fm/c fusion CN Thermalized compound (all degrees equilibrated) Giant Dipole Resonance Damping Mechanism in CN GDR p vs n Pree-equilibrium (charge equilibration) Dynamic Dipole Reaction Dynamics density plot dipole moment CNfusion  exclusive measurements of  10-15 MeV  -rays from fused systems

4. Garfield + Hector Setup @ Laboratori Nazionali di Legnaro HECTOR: 8 Large BaF 2 High-energy  -rays Coincident measurements  + LCP + residues @ 5-20 MeV/A GARFIELD: 180 E-  E telescopes Light Charged Particles PPAC or Phoswich Residues selection Exclusive measurements of  -rays from pre-equilibrated OR Compound Nucleus High-energy  -rays pre equilibrium  spectra GARFIELD+HECTOR Campaign oTemperature dependence of GDR (spokeperson: F. Camera, PRL97(2006)012501) o Isospin Mixing of N=Z nucleus 80 Zr at high T (spokepersons: O. Wieland, S. Barlini) o Dynamic Dipole in N/Z asymmetric reaction (spokeperson: A. Corsi - Milano) o Search for the Jacobi shape transition in light nuclei (spokesperson: A. Maj - Krakow) o Onset of the multi-fragmentation and the GDR (spokeperson: J.P. Wieleczko - GANIL)

5. pre-equilibrium emission in fusion reactions 1. Dynamic Dipole Resonance (DDR) rearrangment of p and n to establish charge-to-mass equilibrium Experimental method comparison high-energy  -ray yield in symmetric/asymmetric reactions (same CN at equal E* and I) Open questions [ Stable Beams] - centroid energy - dependence on E exc - dependence on I B. Martin et al., PLB664(2008)47 Pierroutsakou et al., PRC71(2005)054605 Baran, Brink, Colonna, DiToro PRL87(2001)182501 Simenel et al., PRL86(2001)2971 10-25% 132 Ce* MEDEA-LNS E1 anysotropy

6. HECTOR + GARFIELD experiments @ LNL 8 MeV/A 15 MeV/A pre equilibrium Asymmetric reaction 16 O + 116 Sn  132 Ce* Symmetric  spectrum 8 MeV/A 15 MeV/A DATA A. Corsi et al., to be published Preequilibrium emission is enhanced at high beam energy M. Di Toro. V. Baran, C. Rizzo Reaction dynamics + Bremsstrahlung New GARFIELD proposal @12 MeV/A Comparison with Martin et al., PLB664(2008)47

7. Dynamic Dipole yield increases with asymmetry of fusing ions SPIRAL2 Radioactive Beams LOI SPIRAL2 Dynamic Dipole in 172 Yb  5MeV/A (onset energy for DDR)

8. 2. GDR emission from equilibrated CN Isospin mixing at high T o Isospin is a good quantum number: Nuclear Hamiltonian is symmetric for p and n exchange o Coulomb interaction breaks isospin: at T=0: isospin mixing is small (< 5%) at high T: expected restoration of isospin symmetry  -decay of GDR as a probe of isospin mixing at high T E1 (isovector GDR) transitions I inital = 0  I final = 0 forbidden I inital = 0  I final = 1 allowed in CN:  ( I=0 ) >  ( I=1 )   suppression of  yield from I inital_CN = 0 32 S 31 P N=Z-1 N=Z N ≠ Z Proj Ta CN  I≠0 N=Z N=Z N=Z Proj Ta CN I=0 + I=0  I=0 GDR decay from 2 different CN systems 1% mixing T= 2.7 MeV Z= 16 32 S 31 P N=Z-1 N=Z N ≠ Z Proj Ta CN  I≠0 N=Z N=Z N=Z Proj Ta CN I=0 + I=0  I=0 GDR decay from 2 different CN systems M.Kicinska-Habior et al. Nucl. Phys A731c (2004)13 N=Z GDR Supression depends on degree of mixing Full mixing No – Mixing ~ % Mixing N=Z GDR Supression depends on degree of mixing Full mixing No – Mixing ~ % Mixing GDR from CN 1% mixing T= 2.7 MeV Z= 16

9. T [MeV] T = 2-3 MeV Experiment M. Kicińska-Habior, et al. Present status G. Colo, M.A. Nagarajan, P. Van Isacker, A. Vitturi PRC 52(1995)1175 Bohr Mott. HF deformed RPA BM- Hybrid HF % % % % Theory H. Sagawa, P.F. Bortignon, G. Colo Phys. Lett B444(1998)1 T0T0 Inclusive measurements ONLY - NO residue selection - NO charged particles

10. HECTOR + GARFIELD experiments @ LNL March 2008 T = 2-3 MeV Isospin Mixing in 80 Zr Heaviest N=Z system with STABLE beams only possible at T  0 A 80 Two reactions – Same CN 40 Ca + 40 Ca  80 Zr (I=0) E b =200 MeV 37 Cl + 44 Ca  81 Rb (I≠0) E b =154 MeV Counts [arb. Un.] E  [keV] Radioactive Beams (SPIRAL2 LOI) N=Z: 68 Se, 80 Zr, 84 Mo, 96 Cd, 112 Ba [using 44 Ti, 56 Ni, 72 Kr beams]

11. Collective Rotation o Order-to-Chaos Transition in Warm Nuclei High-K high spin states [fusion evaporation and deep-inelastic] Collective Vibrations o HOT Giant Resonances 1. Dynamic Dipole emission in pre-equilibrium reaction 2. Giant Dipole Resonance: Isospin Mixing at T  0 [fusion evaporation 5-10 MeV/A] o Highly excited low spin states Pygmy states (up to GDR and GQR region) [inelastic scattering with heavy-ions  10MeV/A] Present campaigns and LOI’s AGATA Demonstrator@LNL and SPIRAL2 …

12. Highly excited Pygmy/GR states BnBn I E* Inelastic scattering with Heavy-Ions (~10-20 MeV/A)  -decay measurement with HIGH resolution GDR GQR (p,p’) experiments in STABLE nuclei (  ’) experiments : A=50, A=140 ( ,  ’  ) experiments @ 30 MeV/A T. Hartmann PRL85(2000)274 D. Savran et al., PRL97(2006)172502 140 Ce Fine structure GQR 58 Ni 90 Zr 120 Sn 208 Pb Shevchenko PRL93(2004)122501-1

13. 22 MeV/u 17 O on 208 Pb target Inelastic scattering 17 O @ 20 MeV/A – ALPI on stable 90 Zr, 208 Pb, … target LOI for AGATA Dem. @LNL A. Bracco et al. Beam 17 O Ge array AGATA-Dem Scintillator array (Hector, LaBr 3,..)  E-E Si telescopes @13° GQR experiments in ORNL in ’80s Beam ~ 10 9- 10 10 pps spin spectrometer (72 NaI detectors) silicon detector (6 E-  E telescopes,  900 keV resolution) 7.5 MeV 10 MeV GQR SnSn G.S 0 I g.s. decay 3 - decay 2 + decay 3 - decay  -ray gated spectra J.Beene et al PRC39(1989)1307 J. Beene et al. PRC41(1990)929 F.E.Bertrand et al NPA 482(1988)287c GQR TRACE (ITC-IRST detectors) Segmented Si-pad tecnology Pixel size: 4x4 mm 2 active area: 20x50 mm 2 60 (5x12) pixels Energy Resolution: 1% 6 telescopes 300  m-1mm D. Mengoni and E. Farnea

14. Collective Rotation o Order-to-Chaos Transition in Warm Nuclei High-K high spin states [fusion evaporation and deep-inelastic] Collective Vibrations o HOT Giant Resonances 1. Dynamic Dipole emission in pre-equilibrium reaction 2. Giant Dipole Resonance: Isospin Mixing at T  0 [fusion evaporation 5-10 MeV/A] o Highly excited low spin states Pygmy states (up to GDR and GQR region) [inelastic scattering with heavy-ions  10MeV/A] Present campaigns and LOI’s AGATA Demonstrator@LNL and SPIRAL2 …

15. Order-to-Chaos in warm rotating nuclei  rot I+2 I I-2 Compound Nucleus Chaos Regular bands Order n n n p  - decay B(E2) T=0 01234 s/d p, n resonances Poisson GOE 01234 s/d COLD Bands Poisson GOE Warm Rotation strongly interacting bands Onset of chaos ? T  0.4 MeV U  2-4 MeV I  20  T0U0T0U0 T  0.7 MeV U  8 MeV 168 Yb VALLEY (warm rotation) A.Bracco and S.Leoni, Rep.Prog.Phys. 65 (2002) 299 RIDGES (Order) quasi-continuum   coincidence spectra T0T0

16. EUROBALL (LNL, Strasbourg) First Measurement of Damping Width 163 Er  rot I+2 I I-2 4  geometry > 200 HpGe + AC Shields    10 — 5 %  ( M  =1 – M  =30) Large Gamma Arrays based on Compton Suppressed Spectrometers Future Array: AGATA RIB: Spiral2-LOI’s Onset of Chaos U  1.5 MeV Low-K High-K Low K High K 10 Vanishing of K K S. Leoni et al., PRL93(2004)022501-1 G. Benzoni et al., PLB615(2005)160

17. AGATA Demonstrator @ LNL LOI: Study of the region of Hf nuclei: A=174-182  Classical high-K isomer region 1. Fusion evaporation reaction: Warm rotation up to U  4 MeV 48 Ca (@5MeV/A) + 130 Te  172-176 Hf AD + Multiplicity Filter + RFD 2. Deep-Inelastic reaction: More n-rich nuclei Moderately Warm rotation up to U  1-2 MeV 132 Xe (  15-20% above Coulomb Barrier) + 180 Hf  182-184 Hf AD + PRISMA + Multiplicity Filter Two Possible Reaction mechanisms

18. 27 detectors Helena array : BaF 2 exagonal scintillators 3”x3” 15 cm from target  45% of 4  Total eff.  ~ 30% electronics: AGAVA interface  AGATA detectors @ 14 cm Design Study for Multiplicity Filter couppled to AGATA Demonstrator @ LNL B. Million, Simulations & Ancillary detectors

19. probability M  Fold Usefull to study  high spin states in fusion reaction  low and high M  regimes in deep-inelastic/MNT

20. Participants to the Experiments Milano University & INFN: A. Bracco, G. Benzoni, N. Blasi, S. Brambilla, F. Camera, F. Crespi, S. Leoni, D. Montanari, B. Million, O. Wieland Legnaro National Laboratory: F. Gramegna, G. de Angelis, D. Napoli, L. Corradi, et al. University of Padova & INFN: D. Bazzacco, E. Farnea, S. Lenzi, S. Lunardi, D. Mengoni, et al. Krackow, Poland: A.Maj, M. Kmiecik, P.Bednarczyk, W. Meczynski, J. Styczen, et al. + GARFIELD – AGATA-PRISMA collaborationsSummary Collective modes of excitations (vibrations & rotations) allow to study nuclear structure properties - beyond mean field - at extreme values of SPIN, TEMPERATURE and ISOSPIN Ideal physics cases for Stable/Radioactive beams & new generation detector arrays (AGATA)

21. ZANZAN Z A N+1 Z A N+2 Z A N+3 2+2+ T=0 T≠0 ? Future Perspectives with RIB: Evolutions of Shells at Finite Temperature  rot I+2 I I-2 25% effect mostly due to N A=168 I=40h A=176  rot [keV] Stable beam: 48 Ca + 124 Sn  168 Yb+4n Radioactive beam : 132 Sn + 48 Ca  176 Yb+4n M. Matsuo et al., NPA649(1999)379c

22. GQR GDR 22 MeV/u 17 O on 208 Pb target F.E.Bertrand et al NPA 482(1988)287c @ 13 0 and inelastic scattering ~20 MeV/A change of shape & nucleon distribution  bulk properties nuclear matter  N-N interaction Giant Quadrupole Resonance in 208 Pb and 90 Zr g.s. decay 3 - decay 2 + decay 3 - decay  -ray gated spectra 7.5 MeV 10 MeV GQR SnSn G.S 0 I measured in ORNL in ’80s Beam ~ 10 9- 10 10 pps spin spectrometer (72 NaI detectors) silicon detector (6 E-  E telescopes,  900 keV resolution) J.Beene et al PRC39(1989)1307 J. Beene et al. PRC41(1990)929

23. AGATA Demonstrator LOI High Resolution Measurement of GQR in 208 Pb and 90 Zr nuclei 2 reactions: 1. 208 Pb( 17 O, 17 O’), ~ 20 MeV/A 2. 90 Zr( 17 O, 17 O’), ~ 20 MeV/A AD + Si telescope array Si-CsI detectors,  E-E digital electronics Oxigen

24. Open questions (STABLE beams) Baran, Brink, Colonna, DiToro PRL87(2001)182501 Pierroutsakou et al., PRC71(2005)054605 PDR GDR 8 MeV/A small I in CN large I in CN PDR centroid is predicted at lower energies O+Mo @ 8 MeV/A PDR yield is predicted to depend on E* PDR strength is expected to depend on impact parameter O+Sn @ 8 MeV/A angular distribution check if pure dipole