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Giant resonances, exotic modes & astrophysics 1) The dipole strength : r-process Ultra-High Energy Cosmic Rays 2) Exotic modes : SuperGiant Resonances Giant Pairing Vibrations 3) Surprise ? E. Khan

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1) The dipole strength

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The role of dipole strength in nuclei (de)-excitation r-process : (n, ) rates in the non-equilibrium canonical model Nuclei photodisintegration Statistical model of compound nuclear reaction : Hauser-Feshbach Photon transmission coefficient sensitive to : SnSn TnTn (Z,A) + n (Z,A+1) T T E1 (E) (E) dE 0 S n +E n TT the E1 strength distribution T E1 (E) the level density (E)

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Why using microscopic calculations ? Microscopic Efforts consuming ? More suited to extrapolate far from stability : neutron skin Characterize the n-n interaction on the whole nuclear chart Test the model validity on a large scale Lorentzian (Hybrid)Microscopic Phenomenologic Fast and simple to use Extrapolations ? No feedback about nuclear structure E1

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Impact on astrophysical predictions Effect of the Pygmy Resonance Maxwellian averaged (n, ) rates r-abundance distributions S. Goriely, PLB436 (1998) 10 GDR+PR GDR

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Systematics E1 strength measurements for neutron rich unstable nuclei below S n Relativistic Coulomb excitation : AGATA MeV/u 70 Ni High Z Experiment #1

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HF RPA Meanwhile : microscopic prediction of the E1 strength Collective excitation in superfluid system QRPA in linear response : small amplitude limit of the perturbed TD-HFB equations harmonic oscillations Connected to the Density Functional Theory : Since Year ~ 2000 Skyrme functionnal ρ= : particle density κ= : pairing density E. Khan, N. Sandulescu, Nguyen Van Giai, M. Grasso PRC66 (2002) E (MeV) (fm -3 )

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Comparison with experiment GDR centroids (cf experiment #1) rms on GDR centroids : SIII 2267 keV SGII573 keV SLy4457 keV MSk7564 keV SLy4 (48 spherical nuclei) BSk7 : rms on 2135 masses : 676 keV rms on 48 GDR centroids : 485 keV interactions developed with both ground and excited states features on a large scale

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Experiment #2 Low energy section of EURISOL : masses, decay,... Inputs : E1, level densities, masses, optical model potential Validity : high level density S n not too small Direct captures are not negligible for neutron-rich nuclei

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(n, ) rates Deviation up to a factor 10 QRPA/Hybrid QRPA/QRPA T= K Discrepancy pheno/micro Agreement HF+BCS QRPA / HFB QRPA S. Goriely, E. Khan, M. Samyn, NPA739 (2004) 331

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Are Ultra-High Energy Cosmic Rays made of nuclei ? The Pierre Auger collaboration GRB990123

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Ultra High energy Cosmic Rays E= eV Ankle GZK Redressed spectrum (x E 3 ) ~ E -3

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Composition, acceleration & propagation Open question ! Extra-galactic particles : protons nuclei ( 56 Fe, …) ? Open question ! Gamma Ray Bursts, Active Galaxy Nucleus ? N(E)~E - Quantitative answers Interaction with the 2.7 K Cosmic microwave background Extra-galactic Magnetic fields Comparison with the measured spectrum on Earth (AUGER, …) COMPOSITION : ACCELERATION : PROPAGATION :

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Propagation of UHECR 2.7 K Cosmic Microwave Background Photons density E (MeV) = Lorentz boosted * E (MeV) Photodisintegration cross section GDR = Photodisintegration rate (~1h -1 ) Fe : eV

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Photodisintegration (I) Pheno. and microscopic models to predict the GDR strength Photodisintegration calculated within Hauser-Feshbach formalism 55 Mn ( ,1nx) 51 V ( ,1nx) Full network with beta decay rate (~ r-process)

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: PSB path Z=8 Z=14 Z=18 Z=22 Z=26 Z N A Photodisintegration (II)

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Experiment #3 UHECR campain ? Usefull for many other applications E1 strength for A<56 nuclei close to the valley of stability Very High intensity : 10 9 pps for 37,39 Ar

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Impact on astroparticle propagation Source : 56 Fe E. Khan, S. Goriely, D. Allard, E. Parizot, et al, Astr. Phys. 23 (2005) 191

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Needs for a galactic CR : Ankle is the galactic/extra-galactic transition Protons only : =2.6 Protons & Nuclei : =2.3 Interpretation of the ankle D. Allard, E. Parizot, A.V. Olinto, E. Khan, S. Goriely, A&A 443 (2005) 29

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2) Exotic modes

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SuperGiant Resonances in neutron stars Nuclear matter : not only a toy for theoreticians

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The inner crust Wigner-Seitz cells ~ ~ 0.5

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Supergiant resonances L=1 L=2 71% EWSR QRPA HFB E. Khan, N. Sandulescu, Nguyen Van Giai, PRC71 ( ~ Excitations of drip-line nuclei immersed in neutron gas

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Experiment #4 Specific heat : spectroscopy of drip-line nuclei drives the excitation spectrum of the Wigner-Seitz cells (low-lying states) Coulex or integrated (p,p’) on the most neutron-rich Sn available ( 138 Sn)

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Giant pairing vibrations Khan PRC69(2004) n transfer GPV : high energy mode never observed 22 O+2n

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Experiment #5 Exotic nuclei : Q value matched for high energy states Search for the GPV 208 Pb ( 12 Be, 10 Be) at ~ 10 MeV/u

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3) Surprise

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GMR in unstable nuclei MAYA active target 56 Ni(d,d’) at 50 MeV/u (GANIL)

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PRELIMINARY E* (MeV) N (/500 keV) 56 Ni excitation energy spectrum Charlotte Monrozeau PhD thesis

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Outlook Dipole modes plays a crucial role in nuclei de-excitation Microscopic treatment necessary to draw conclusions on r-process abundances Nature of UHECR Needs for Masses, decay Systematic E1 data Low lying states close to the drip-line 2 neutron transfer reactions with exotic nuclei Collective excitations in stable nuclei exotic nucleidrip-line nuclei Fermi gas

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Finite temperature effects HFB+QRPA Future : - microscopic treatment of the width - better treatment for odd nuclei - microscopic treatment of the deformation - phonon coupling calculations - drip-line nuclei : coupling between continuum and pairing effects : exact continuum calculations Microscopic models improvements Neutron average pairing field Pairing phase transition T (MeV) n (MeV) 124 Sn

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Comparison with the data Monte-Carlo using a extragalactic source with energy distribution ~ E - CMB : *Protons : photoproduction and e+-e- pairs production *Nuclei : photodisintegration and e+-e- production Infra Red background Non-negligible effect with the forthcoming AUGER data

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Magnetic field effect on the propagation of UHECR Nuclei in the acceleration process Comparison with the AUGER data Next

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Low and high density WS cells Skyrme-HFB calculations with density dependent pairing interaction Non-zero value of at the border of the WS cell Size of the WS cells : 1800 Sn : 28 fm 982 Ge : 14 fm N. Sandulescu PRC 69 (2004)

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1800 Sn Specific heat of collective modes L=0 4 Entropy : S coll =S QRPA -S HFB

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Température dans les noyaux Transition de phase superfluide Noyaux exotiques chauds : pairing+continuum+température E. Khan, Nguyen Van Giai, M. Grasso NPA731(2004)311

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Accelerators of the Universe GRB GANIL

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SLy4 force The QRPA residual interaction Skyrme force and surface pairing interaction E QP < 60 MeV

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