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Giant resonances, exotic modes & astrophysics

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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Giant resonances, exotic modes & astrophysics

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  1. 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

  2. 1) The dipole strength

  3. 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 0 (Z,A+1) • Photon transmission • coefficient sensitive to : Tg • the E1 strength distribution TE1(E) • the level density r(E)

  4. Lorentzian (Hybrid) Microscopic 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 E1 E1

  5. 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

  6. Experiment #1 • Systematics E1 strength measurements for neutron rich unstable nuclei • below Sn • Relativistic Coulomb excitation : AGATA 70Ni High Z 70-100 MeV/u

  7. RPA HF 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 E (MeV) r (fm-3) E. Khan, N. Sandulescu, Nguyen Van Giai, M. Grasso PRC66 (2002) 024309

  8. Comparison with experiment GDR centroids (cf experiment #1) SLy4 rms on GDR centroids : SIII 2267 keV SGII573 keV SLy4457 keV MSk7564 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)

  9. 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, ...

  10. (n,g) rates QRPA/Hybrid Discrepancy pheno/micro QRPA/QRPA Agreement HF+BCS QRPA / HFB QRPA T=1.5 109 K Deviation up to a factor 10 S. Goriely, E. Khan, M. Samyn, NPA739 (2004) 331

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

  12. Ultra High energy Cosmic Rays E=1018-21 eV GZK Ankle ~ E-3 Redressed spectrum (x E3)

  13. 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, …)

  14. Propagation of UHECR 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)

  15. 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)

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

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

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

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

  20. 2) Exotic modes

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

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

  23. L=2 QRPA HFB 71% EWSR Supergiant resonances L=1 ~ Excitations of drip-line nuclei immersed in neutron gas E. Khan, N. Sandulescu, Nguyen Van Giai, PRC71 (2005 042801

  24. 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 (138Sn)

  25. Giant pairing vibrations 22O+2n • 2n transfer • GPV : high energy mode • never observed Khan PRC69(2004)014314

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

  27. 3) Surprise

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

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

  30. 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 nucleiexotic nuclei drip-line nuclei Fermi gas

  31. 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)

  32. 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

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

  34. 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 rat the border of the WS cell N. Sandulescu PRC 69 (2004) 045802

  35. L=0 4 Specific heat of collective modes 1800Sn Entropy : Scoll=SQRPA-SHFB

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

  37. GRB GANIL Accelerators of the Universe

  38. The QRPA residual interaction Skyrme force and surface pairing interaction h SLy4 force EQP < 60 MeV

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