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13-15 October 2008 LNS – INFN Catania

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

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13-15 October 2008 LNS – INFN Catania

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

  2. Collective Vibrations • 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] • Highly excited low spin states • Pygmy states (up to GDR and GQR region) [inelastic scattering with heavy-ions  10MeV/A] Collective Rotation • Order-to-Chaos Transition in Warm Nuclei • High-K high spin states [fusion evaporation and deep-inelastic] Present campaigns and LOI’s AGATA Demonstrator@LNL and SPIRAL2 …

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

  4. Exclusive measurements of g-rays from pre-equilibrated OR Compound Nucleus a spectra High-energy g-rays pre equilibrium Garfield + Hector Setup @ Laboratori Nazionali di Legnaro Coincident measurements g + LCP + residues @ 5-20 MeV/A PPAC or Phoswich Residues selection • GARFIELD+HECTOR Campaign • Temperature dependence of GDR (spokeperson: F. Camera, PRL97(2006)012501) • Isospin Mixing of N=Z nucleus 80Zr at high T (spokepersons: O. Wieland, S. Barlini) • Dynamic Dipole in N/Z asymmetric reaction (spokeperson: A. Corsi - Milano) • Search for the Jacobi shape transition in light nuclei (spokesperson: A. Maj - Krakow) • Onset of the multi-fragmentation and the GDR (spokeperson: J.P. Wieleczko - GANIL) GARFIELD: 180 E-DE telescopes Light Charged Particles HECTOR: 8 Large BaF2 High-energy g-rays

  5. 10-25% 1. Dynamic Dipole Resonance (DDR) pre-equilibrium emission in fusion reactions rearrangment of p and n to establish charge-to-mass equilibrium Experimental method comparison high-energy g-ray yield in symmetric/asymmetric reactions (same CN at equal E* and I) 132Ce* Open questions [Stable Beams] - centroid energy - dependence on Eexc - dependence on I E1 anysotropy MEDEA-LNS 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

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

  7. SPIRAL2 Radioactive Beams Dynamic Dipole yield increases with asymmetry of fusing ions LOI SPIRAL2 Dynamic Dipole in172Yb  5MeV/A (onset energy for DDR)

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

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

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

  11. Collective Vibrations • 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] • Highly excited low spin states • Pygmy states (up to GDR and GQR region) [inelastic scattering with heavy-ions  10MeV/A] Collective Rotation • Order-to-Chaos Transition in Warm Nuclei • High-K high spin states [fusion evaporation and deep-inelastic] Present campaigns and LOI’s AGATA Demonstrator@LNL and SPIRAL2 …

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

  13. GQR experiments in ORNL in ’80s Beam ~ 109-1010 pps spin spectrometer (72 NaI detectors) silicon detector (6 E-DE telescopes, 900 keV resolution) GQR LOI for AGATA Dem. @LNL A. Bracco et al. g-ray gated spectra g.s. decay TRACE (ITC-IRST detectors) Segmented Si-pad tecnology Inelastic scattering 17O @ 20 MeV/A – ALPI on stable 90Zr, 208Pb, … target 3- decay 2+ decay Ge array AGATA-Dem Scintillator array (Hector, LaBr3,..) 3- decay Pixel size: 4x4 mm2 active area: 20x50 mm2 60 (5x12) pixels Energy Resolution: 1% 10 MeV GQR 6 telescopes 300mm-1mm 7.5 MeV Beam 17O Sn I 0 G.S DE-E Si telescopes @13° 22 MeV/u 17O on 208Pb target D. Mengoni and E. Farnea J.Beene et al PRC39(1989)1307 J. Beene et al. PRC41(1990)929 F.E.Bertrand et al NPA 482(1988)287c

  14. Collective Vibrations • 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] • Highly excited low spin states • Pygmy states (up to GDR and GQR region) [inelastic scattering with heavy-ions  10MeV/A] Collective Rotation • Order-to-Chaos Transition in Warm Nuclei • High-K high spin states [fusion evaporation and deep-inelastic] Present campaigns and LOI’s AGATA Demonstrator@LNL and SPIRAL2 …

  15. GOE p, n resonances RIDGES (Order) Poisson VALLEY (warm rotation) 168Yb 0 1 2 3 4 s/d I+2 Onset of chaos ? T  0.4 MeV U  2-4 MeV I  20  I I-2 T0 Warm Rotation strongly interacting bands Poisson COLD Bands Grot n n quasi-continuum g-gcoincidence spectra GOE n p 0 1 2 3 4 s/d A.Bracco and S.Leoni, Rep.Prog.Phys. 65 (2002) 299 Order-to-Chaos in warm rotating nuclei Compound Nucleus Chaos T0.7 MeV U8 MeV g-decay B(E2) T0 U0 Regular bands Order T=0

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

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

  18. Design Study for Multiplicity Filter couppled to AGATA Demonstrator @ LNL B. Million, Simulations & Ancillary detectors 27 detectors Helena array: BaF2 exagonalscintillators3”x3” 15 cm from target W = 45% of 4p Total eff. e~ 30% electronics: AGAVA interface  AGATA detectors @ 14 cm

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

  20. Summary 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) 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 collaborations

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

  22. g-ray gated spectra measured in ORNL in ’80s Beam ~ 109-1010 pps spin spectrometer (72 NaI detectors) silicon detector (6 E-DE telescopes, 900 keV resolution) g.s. decay GQR 3- decay GDR 2+ decay 3- decay F.E.Bertrand et al NPA 482(1988)287c 10 MeV GQR 7.5 MeV Sn I 0 G.S 22 MeV/u 17O on 208Pb target J.Beene et al PRC39(1989)1307 J. Beene et al. PRC41(1990)929 and @ 130 Giant Quadrupole Resonance in 208Pb and 90Zr inelastic scattering ~20 MeV/A • change of • shape & nucleon • distribution • bulk properties nuclear matter • N-N interaction

  23. AGATA Demonstrator LOI High Resolution Measurement of GQR in 208Pb and 90Zr nuclei Si-CsI detectors, DE-E digital electronics 2 reactions: 1.208Pb(17O,17O’), ~ 20 MeV/A 2.90Zr(17O,17O’), ~ 20 MeV/A AD + Si telescope array Oxigen

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

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