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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,g) rates in the non-equilibrium canonical model Nuclei photodisintegration Statistical model of compound nuclear reaction : Hauser-Feshbach Tn Sn+En (Z,A) + n Tg = TE1(E) r(E) dE Sn (Z,A+1) Photon transmission coefficient sensitive to : Tg the E1 strength distribution TE1(E) the level density r(E)

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**Why using microscopic calculations ?**

Phenomenologic Fast and simple to use Extrapolations ? No feedback about nuclear structure 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 E1 E1

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**Impact on astrophysical predictions**

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

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

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**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 : e[r,k] Since Year ~ 2000 Skyrme functionnal ρ=<ψ+(r)ψ(r)> : particle density κ=<ψ(r)ψ(r)> : pairing density HF RPA E (MeV) r (fm-3) E. Khan, N. Sandulescu, Nguyen Van Giai, M. Grasso PRC66 (2002)

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**Comparison with experiment**

GDR centroids (cf experiment #1) SLy4 rms on GDR centroids : SIII keV SGII 573 keV SLy4 457 keV MSk7 564 keV 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 (48 spherical nuclei)

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**Low energy section of EURISOL : masses, b decay, ...**

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

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**(n,g) rates QRPA/Hybrid Discrepancy pheno/micro QRPA/QRPA**

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

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**Are Ultra-High Energy Cosmic Rays**

made of nuclei ? GRB990123 The Pierre Auger collaboration

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**Ultra High energy Cosmic Rays**

E= eV GZK Ankle ~ E-3 Redressed spectrum (x E3)

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**Composition, acceleration & propagation**

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

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**= * Propagation of UHECR Photodisintegration rate (~1h-1)**

2.7 K Cosmic Microwave Background Photodisintegration cross section g=2.1010 GDR 56Fe : 1021 eV * Photons density Lorentz boosted 10 100 0.1 1 10 100 1000 = E (MeV) E (MeV) Photodisintegration rate (~1h-1)

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**Photodisintegration (I)**

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

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**Photodisintegration (II)**

55 54 53 52 51 50 49 48 47 45 44 43 41 40 38 39 37 36 34 35 30 26 22 18 15 14 13 11 9 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 35 36 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 13 12 11 10 : PSB path Z=8 Z=14 Z=18 Z=22 Z=26 Z N A Photodisintegration (II)

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**Usefull for many other applications**

Experiment #3 E1 strength for A<56 nuclei close to the valley of stability Very High intensity : 109 pps for 37,39Ar UHECR campain ? Usefull for many other applications

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**Impact on astroparticle propagation**

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

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**Interpretation of the ankle**

Protons only : b=2.6 Protons & Nuclei : b=2.3 Needs for a galactic CR : Ankle is the galactic/extra-galactic transition 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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**not only a toy for theoreticians**

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

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The inner crust ~ r0 ~ 0.5 r0 Wigner-Seitz cells

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**Supergiant resonances**

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

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**Experiment #4 on the most neutron-rich Sn available (138Sn)**

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 (138Sn)

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**Giant pairing vibrations**

2n transfer GPV : high energy mode never observed Khan PRC69(2004)014314

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**Experiment #5 208Pb(12Be,10Be) at ~ 10 MeV/u**

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

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3) Surprise

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

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

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**PRELIMINARY Charlotte Monrozeau PhD thesis**

56Ni excitation energy spectrum PRELIMINARY E* (MeV) N (/500 keV) 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, b 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 nuclei drip-line nuclei Fermi gas

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**Microscopic models improvements**

Neutron average pairing field 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 124Sn Dn (MeV) Pairing phase transition T (MeV)

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**Comparison with the data**

Monte-Carlo using a extragalactic source with energy distribution ~ E-b CMB : *Protons : p 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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**Next Magnetic field effect on the propagation of UHECR**

Nuclei in the acceleration process Comparison with the AUGER data

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**Low and high density WS cells**

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

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**Specific heat of collective modes**

1800Sn Entropy : Scoll=SQRPA-SHFB L=

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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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**The QRPA residual interaction**

Skyrme force and surface pairing interaction SLy4 force h EQP < 60 MeV

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