Recent developments and perspectives in NUCLEAR STRUCTURE by gamma and particle spectroscopy

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1 Milano, -29 June 17 Recent developments and perspectives in NUCLEAR STRUCTURE by gamma and particle spectroscopy Silvia Leoni UNIMI/INFN: A. Bracco, F. Camera, F.C.L. Crespi, S. Bottoni, S. Leoni, A. Mentana, A. Pullia, S. Capra, S. Riboldi, P.F. Bortignon, G. Colò INFN: G. Benzoni, B. Blasi, C. Boiano, S. Brambilla, B. Million, O. Wieland, E. Vigezzi INFN-CNS3-GAMMA: MI, PD, LNL, FI, PG Interna6onal collabora6ons within EUROPE, JAPAN, USA

2 INTRODUCTION Challenges in Nuclear Physics o The Physics more than 7000 Nuclei! o Interdisciplinarity - Astrophysics o Dedicated Facility/Detection Setups γ spectroscopy FOCUS on NUCLEAR STRUCTURE Selected Recent Highlights o Shape Coexistence o Collective Excitations Resonances o Complex Excitations Coupling Particles and Phonons o OUTLOOK how to pin down the nuclear force

3 Our Challenge: UNIFIED Description of ALL Nuclei in the Universe (EXOTIC) NUCLEI Very Proton number Z ~3000 discovered Stable 126 BASIC SCIENCE > 7000 estimated to exist in the Universe Enormous Discovery Potential!!! n Neutron number N p Many Body Quantum System Symmetry Principle Effective Nuclear Force

4 Our Challenge: UNIFIED Description of ALL Nuclei in the Universe (EXOTIC) NUCLEI Proton number Z 8 16 O DIPOLE Neutron SKIN OSCILLATION Excitations 48 Ca Sn 78 Ni Sn Halos Clusters Shapes 8 Pb BASIC SCIENCE n Many Body Quantum System SHELL Structure Magic Numbers Neutron number N p Symmetry Principle Effective Nuclear Force VERY COMPACT OBJECT up to ~ 250 nucleons SIZE ~ m 3 DENSITY ~ kg/m 3

5 Proton number Z 2 8 STRONG Interdisciplinary with... ASTROPHYSICS in STAR explosions Stable 126 Rapid Capture of FREE Neutrons β-decay towards stable Isotopes BASIC SCIENCE From EXOTIC To STABLE Nuclei n Many Body Quantum System Neutron number N p Symmetry Principle Effective Nuclear Force

6 Proton number Z APPLICATIONS Reactors, STRONG Interdisciplinary with... ASTROPHYSICS Radio isotopes, BASIC SCIENCE Heavy Elements ABUNDANCES depends on Structure of UNKNOWN EXOTIC Nuclei Magic Numbers, Shapes τ β Spherical ~ 10 x τ β Deformed P n Spherical ~ 0.5 x P n Deformed n Many Body Quantum System Neutron number N p Symmetry Principle Effective Nuclear Force

7 A World Wide Effort to Expand the Nuclear Chart PRODUCTION: stable and radioactive ion beams, neutron beams, INVESTIGATION of Nuclear Structure: gamma and particle spectroscopy Theory Institute of Nuclear Physics SEATTLE (USA) Theory ECT* European Center TRENTO (ITALY) TRIUMF MSU Argonne GANIL GSI ISOLDE-CERN Orsay ILL-Grenoble Bucharest LAB Legnaro LAB Sud LAB Gran Sasso OSAKA RIKEN

8 LONG TRADITION OF γ-spectroscopy Arrays based on Compton suppressed Ge detectors from the 80 s: TESSA (Daresbury) OSIRIS (Berlin) ARGONNE-ND ARRAY (Argonne) NORDBALL (Copenhagen) JUROSPHERE (Jyvaskyla) EUROGAM (Strasbourg) CLARION (Oak Ridge) GASP/GALILEO (Legnaro) EUROBALL (Legnaro, Strasbourg) GAMMASPHERE EUROBALL Legnaro, Strasbourg GASP Legnaro EUROGAM Daresbury

9 STATE of the ART Ge ARRAYS AGATA (Advanced-GAmma-Tracking-Array) GRETA (Gamma-Ray Energy Tracking Array) LNL, 11 S. Akkoyun et al, NIMA 668 (12) LBNL, 11 S. Paschalis et al, NIMA 709 (13) The Ge Arrays ² EFFICIENCY: 43% M γ = 1 and % Mγ = 30 (@ 1 MeV, FULL BALL) ² COUNT RATE capabilires (100s KHz) ² ANGULAR RESOLUTION of the γ interacron point (θ~1 o ) ² PERFECT DOPPLER CORRECTION (6 1 MeV, β=50%)

10 HARDWARE The Gamma Tracking Array Concept SOFTWARE

11 LNL: crystals (5TC) Total Eff. ~6% 1/12 FULL BALL AGATA Inauguration: 9 th April 10 Legnaro National Laboratory INFN Physics LNL (10-11) Most Relevant Results from Milano 2 Phys. Rev. Lett. 1 Review Paper Several Phys. Rev. C Legnaro

12 The AGATA Towards 1π LNL: crystals Total Eff. ~6% GSI: crystals Total Eff.~10% MILANO LaBr 3 Detectors GANIL: up to 45 crystals Total Eff. ~22% Demonstrator + PRISMA backward STABLE BEAMS experiments AGATA + FRS forward RELATIVISTIC EXOTIC BEAMS 7 experiments AGATA+VAMOS+ backward EXOTIC (ISOL) & STABLE BEAMS 6 experiments in 15 à From at Legnaro-INFN (SPES Radioac@ve ISOL Beams)

13 AGATA - FULL Detector 180 crystals segmented (6480 segments) 60 triple clusters 2.5 tons FULLY DIGITAL electronics Solid ang. % Eff. 43% (M γ =1) P/T 58% (M γ =1) A. Bracco, Chair

14 Detection Systems (State of the Art ) Very Powerful and Complete Experimental Setups... charged-particle Spectroscopy Si stripped/pixel detectors neutron identification AGATA MINIBALL TREX MUGAST EXOGAM GALILEO LNL Gamma spectroscopy HPGe, scintillators Magnetic Spectrometer Large Acceptance NEDA/NWALL PARIS Labr3+NaI VAMOS PRISMA

15 Selected Recent Highlights of γ spectroscopy DIPOLE Proton number Z 8 16 O Neutron SKIN OSCILLATION Excitations Pygmy Resonances 48 Ca Sn 78 Ni Sn 8 Pb 126 Shape Coexistence Ni - isotopes Couplings Particle-Phonon 133 Sb = 132 Sn + 1 proton Neutron number N

16 Appearence of DIFFERENT SHAPES in the SAME NUCLEUS at low excitation energy Secondary Minima in the Potential Energy Surface PES METASTABLE Configurations SHAPE ISOMERS in A=240 Polikanov 1973 TWO SEPARATE WORLDS Conformational ISOMER Butane Molecule C 4 H 10 γ 95% 10-7 W.u. 5% FREE Energy Present Challenge in Nuclear Physics: MICROSCOPIC description Emergence of SHAPES and DEFORMATION in a pure SHELL Model framework (individual nucleons + interaction)

17 MICROSCOPIC Structure of Nuclei: a computational challenge 6 ħω Shell Structure for p and n Divergent Dimension of Configuration Space State-of-the-art SHELL Model possible for A< ħω 126 Number of ways to distribute A nucleons over K orbitals new calculations scheme Monte Carlo Approach Effective N-N interaction 4 ħω 3 ħω 2 ħω 1 ħω 0 ħω Number of configurations Ru 10 N=Z 56 Ni Cr Ti 10 4 very powerfull computer 10 6 parallel processors K-Computer Tokio University (Prof. Taka Otsuka s group)

18 Monte Carlo SHELL Model (T. Otsuka s Group) 66 Ni 70 Ni: COEXISTENCE of spherical, oblate and prolate SHAPES Best Candidate for SHAPE isomerism HINDERED γ-decay PROLATE à SPHERICAL 66 Ni Confirmed by Experiment!!! 18 O + 64 Ni à 16 O + 66 Ni, below Coulomb barrier prolate spherical oblate à (7) ps 0.2 W.u Spherical g.s. 66 Ni STEP FORWARD in understanding MICROSCOPIC origin of deformation à VALIDATION of PREDICTIVE POWER of Most Advanced SHELL Model predictions S.Leoni, B. Fornal et al., Phys. Rev. LeJ. 118, (17) Editor s Sugges6on Complementary studies in Ni chain by β-decay: G. Benzoni et al.,

19 Selected Recent Highlights of γ spectroscopy DIPOLE Proton number Z 8 16 O Neutron SKIN OSCILLATION Excitations Pygmy Resonances 48 Ca Sn 78 Ni Sn 8 Pb 126 Shape Coexistence Ni - isotopes Neutron number N

20 Relevant ENERGY window for (γ,n) reactions in STARS The DIPOLE Response In Nuclei STRONG Impact on Element Abundance Exp n PYGMY RESONANCES with pygmy Theory Few % S n GIANT Neutron Pressure from SKIN Relevant for NEUTRON STARS Radii ASTROPHYSICS Implications o Nucleosynthesis o Neutron Stars Relevance in Nuclear Structure o Complex Microscopic Nature

21 Pygmy Resonances in STABLE NUCLEI Heavy-Ion Inelastic Scattering: a probe sensitive to the surface ΔE-E pixel telescopes LNL Campaign AGATA + Si Telescopes + Scintillators (LaBr3) 17 MeV/A on 8 Pb, 124 Sn, 90 Zr, 140 Ce STABLE targets Pygmy Strength (E1) 1-3% EWSR isoscalar E1 See POSTER F. Crespi

22 A NEW OBSERVATION: 124 Sn QUADRUPOLE PYGMY Multitude of 2 + discrete states 124 Sn( 17 O, 17 O γ) AGATA Review Paper E1 E2 A. Bracco, F. Crespi, E.Lanza, Eur. Phys. J. A51 (15) 99 GQR ConcentraRon of E2 Strength much below the GIANT QUADRUPOLE resonance - In agreement with Quasi-phonon Model predicrons -

23 Pygmy Resonances in EXOTIC NUCLEI Relativistic Coulomb Excitation: high selectivity for E1 excitation Experimental Area Ion Source Up to 1 GeV/ nucleon (90% c) 68 Ni 3- MeV/nucleon (8-% c) GSI FIRST Case: EUROBALL + BaF2 Setup PYGMY Strength: 5-9 % EWSR AGATA + LaBr3 Setup v/c = 73% Preliminary 64 Fe Above background O.Wieland, A. Bracco et al., PRL 102, (09) R. Avigo, O.Wieland, in preparation

24 Complementary program at RIKEN-Japan PYGMY studies in the MOST EXOTIC Nuclei:,22,24 O, 50,52 Ca, 70,72 Ni, 1,132 Sn 8 large LaBr 3 (Milano) ε=1-2%@ 10 MeV Evolution of PYGMY strength along isotopic chains Analysis DALI NaI ε=4%@ 10 MeV Ca Ni Ongoing Experimental Campaign (A. Bracco, F. Camera, F. Crespi, O. Wieland, )

25 Selected Recent Highlights of γ spectroscopy DIPOLE Proton number Z 8 16 O Neutron SKIN OSCILLATION Excitations Pygmy Resonances 48 Ca Sn 78 Ni Sn 8 Pb 126 Shape Coexistence Ni - isotopes Couplings Particle-Phonon 133 Sb = 132 Sn + 1 proton Neutron number N

26 Couplings between Particle and Collective Degrees of Freedom In NUCLEI Particle-Phonon Couplings PHONONS = Vibrations of MAGIC Core 133 Sb = 132 Sn + 1 proton 133 Sb 132 Sn (phonon) In CONDENSED MATTER Electron-Phonon Couplings Phonons and Plasmons 132 Sn Key Ingredient for: - Anharmonicity of vibrational spectra - Damping of Giant Resonances à emergence of COMPLEX excitations Key Ingredient for: - Electromagnetic Response - Superconductivity in Metal Clusters, Fullerenes, Common many-body diagrammatic techniques Different energy scales

27 Particle-Phonon Couplings around EXOTIC and Doubly Magic 132 Sn Neutron-induced FISSION n U n Pu n Pu n U Proton number Z Ni 133 Sb 132 Sn 132 Sn r-process Sb: 132 Sn + 1 π One-valence Proton nucleus Neutron number N

28 The γ-spectroscopy ILL-Reactor (Grenoble) 12-13: 100 days, 95% DATA taking 10 EXOGAM 6 Ge GASP 58 MW MOST INTENSE Con@nuum neutron source In pile Φ n = n cm -2 s -1 Dedicated ballis@c neutron guide highly collimated beam (1 cm 2 ) cold neutrons (mev) Φ n = n cm -2 s -1

29 Fission Data 133 Sb = 132 Sn + 1 proton LifeRme measurements with fast scinrlltors B(M1) [W.u.] 15/2 + à 13/ /2 + à 11/ !! < ps 31(8) ps 17µs Nature of the States is COMPLEX and DIVERSE Interpretation NOT Doable by SHELL Model: Too LARGE space à AlternaRve Approach

30 The New HYBRID Model (G. Colò, P.F. Bortignon - Milano) CORE ExcitaRons (Phonons-RPA) + single parrcle (Hartree Fock) 133 Sb: 132 Sn + 1π Coupling Matrix Elements between SINGLE PARTICLE and CORE excitations consistently calculated RPA (Skyrme X) Hartree Fock (Skyrme X) Phonons and less collective excitations Coupling NO FREE PARAMETERS - Same SkX Interaction G. Colò, P.F. Bortignon, G. Bocchi, Phys. Rev. C 95, (17)

31 The New HYBRID Model (G. Colò, P.F. Bortignon - Milano) CORE ExcitaRons (Phonons-RPA) + single parrcle (Hartree Fock) 133 Sb: 132 Sn + 1π o o GOOD Reproduction of Exp. MIXED States based on Collective and Non-Collective Excitations of 132 Sn CORE B(M1) from lifetimes STARTING POINT for extended investigation in MEDIUM/HEAVY Nuclei NOT possible with SHELL MODEL!!! G. Bocchi, S. Leoni, B. Fornal et al., Phys. Lett. B 760, 273 (16) See POSTER S. Bottoni 16 HIGHLIGHT Institut Laue-Langevin (ILL)

32 OUTLOOK: pinning down the NATURE of the nuclear force Major problem in Nuclear Physics: detail composition of the nuclear force is NOT known!!! Bare N-N interaction can be derived from QCD QCD In HEAVY-Systems: Effective N-N Interaction Corrections are needed due to the presence of other Nucleons LIGHT systems ONLY (up to C, O, Ne, ) can be computed by ab-initio calculations: à they are sensitive to details of the N-N interaction (2 body and 3 body terms) τ (2+) 0.25 ps 0.08 ps 2 body 3 body 16 C AGATA exp. in GANIL - in 10 days: 18 O (141 MeV) U (10 mg/cm 2 ) γ-spectroscopy of n-rich B-C-O-F nuclei High Precision Lifetimes measurements τ = 100 fs 10 s ps

33 Conclusions o NUCLEAR STRUCTURE PHYSICS aims at a unified description of > 7000 Nuclei in the Universe less than half are known... very high discovery potential!!! o Several BASIC questions to be answered Microscopic Origin of shapes and deformations Nature of Resonance Excitations neutron skins Emergence of complex excitations particle-phonon couplings Outlook: sensitivity to details of nuclear force o Strong Interdiciplinarity Astrophysics o State-of-the-Art SETUP: AGATA, large volume scintillators, o A Major Challenge for THEORY ** Thank You for the Attention **