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Complete dipole response in 208 Pb from high-resolution polarized proton scattering at 0°*

Complete dipole response in 208 Pb from high-resolution polarized proton scattering at 0°*. Iryna Poltoratska Institut für Kernphysik, Technische Universität Darmstadt. Complete dipole strength: what can be learned? Polarized protons scattering at RCNP Results Summary and outlook.

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Complete dipole response in 208 Pb from high-resolution polarized proton scattering at 0°*

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  1. Complete dipole response in 208Pb from high-resolution polarized proton scattering at 0°* Iryna Poltoratska Institut für Kernphysik, Technische Universität Darmstadt • Complete dipole strength: what can be learned? • Polarized protons scattering at RCNP • Results • Summary and outlook

  2. Complete dipole strength: what can be learned? • Spinflip M1 strength • Electric pygmy dipole resonance (PDR) • Dipole polarizability • Characteristic scales of the GDR fine structure • 1- states level density from the fine structure of the GDR • Photon strength function Test of microscopic models Measure of neutron skin and symmetry energy Dominant damping mechanism Test of the Axel-Brink hypothesis | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  3. Spinflip M1 Strength • Isovector part: analog of GT modes with T = T0 • Spinflip M1 resonance is quenched • in fp-shell nuclei similar to GT strength • in heavy nuclei – little data →208Pb as a test case • Problem studied in the 80’s but: • large experimental uncertainties • improved model calculations • new experimental access by (p,p´) • intermediate energy region optimal for spin-isospin excitations • at 0° →selectivity on DL=0 transitions • isovector spinflip M1 transitions enhanced | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  4. Electric Pygmy Dipole Resonance (PDR) • PDR: resonance-like structure, typically close to neutron threshold • Strength related to neutron excess • measure of neutron skin • measure of the density dependence of the asymmetry energy • Strength distribution around neutron threshold relevant for nucleosynthesis (r-process) | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  5. Nuclear Dipole Polarizability • Static nuclear dipole polarizability P.G. Reinhard, W. Nazarewicz, PRC 81 (2010) 051303 (R) J. Piekarewicz, arXiv:1012.1803v1 [nucl-th] 8 Dec 2010 • → measure of the neutron skin PDR strength ? Polarizability Neutron skin EoS of neutron-rich matter | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  6. Photon Strength Function (PSF) • Describes the (average) energy distribution of photon emission from highly-excited states or cross section for photon absorption (principle of detailed balance) Average decay width from level i to g.s. | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  7. Axel-Brink Hypothesis • Strength: • depends only on Eg • is independent of the initial state structure: excitation energy (T), Jp,… • Same PSF holds for absorption and gamma emission | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  8. Experimental Discrepances in PSF ? Ann-Cecilie Larsen, Workshop on Gamma Strength and Level Density, Dresden-Rossendorf, August 2010 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  9. Problems G. Rusev et al., PRC 79 (2009) 061302 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  10. Problems (continued) • (g,xn) reactions provide information only above threshold • Decay reactions • normalization at the Snenergy • Level densities needed • Consistent measurements below and above • the threshold needed | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  11. Complete E1 and M1 Strength Distributions • Polarizedprotonscatteringat0o • intermediate energy: 300 MeV optimal forspin/isospin excitations • Coulomb excitationof1-states • high resolution: ΔE = 25 keV (FWHM) • angular distributions: E1 / M1separation • polarizationobservables: spinflip / non-spinflipseparation • 208Pb as a referencecase | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  12. 0o Setup at RCNP Measured observables: ds/dW - angular distributions 0° Q  10° Ay - asymmetry DSS at 0° - sideways polarization observables DLL at 0° - longitudinal polarization observables | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  13. Measured SpectrumBackground-Subtracted Spectrum • Pronounced fine structure of the GDR is recognized • Strong Coulomb excitation of the GDR at 0° | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  14. Measured Spectrum: Low-Energy Part • All dipole transitions known from (g,g´) are observed | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  15. Coulomb Exitations of 1- States | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  16. E1/M1 Decomposition by Spin Observables Poster J. Simonis, HK 33.4 T. Suzuki, Prog.Theo.Phys. 103 (2000) 859 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  17. Decomposition into Spinflip / Non-Spinflip Cross Sections | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  18. Multipole Decomposition of Angular Distributions | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  19. Multipole Decomposition of Angular Distributions | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  20. Comparison of Both Methods I Total DS = 1 DS = 0 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  21. B(E1) Strength: Low-Energy Region Ec = 7.30 MeV Ec = 7.43 MeV • Extracted assuming semiclassical Coulomb excitation | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  22. B(E1) Strength: GDR | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  23. E1 Response in 208Pb: Experiment vs. Theory V.Yu. Ponomarev 3p – 3h for Ex ≤ 10 2p – 2h for GDR Priv. com. E. Litvinova et al., 1p - 1h  phonon PRC 78 (2008) 014312, PRC 79 (2009) 054312 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  24. 0–8.2 MeV 8.2–19 MeV Dipole Polarizability of 208Pb aD (fm3 / e2) Present averaged 0.82 15.7 16.52 2.34 20.1 22.44 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  25. Polarizability as a Measure of the Neutron Skin rskin = 0.155(23) fm * P.G. Reinhard and W. Nazarewicz PRC 81 (2010) 051303 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  26. Extraction of level density • Determinedfromfluctuationanalysisofthefinestructureofthe GDR S. Müller, F. Beck, D. Meuer, and A. Richter, Phys. Lett. 113B (1982) 362 P.G. Hansen, B. Jonson, and A. Richter, Nucl. Phys. A518 (1990) 13 • Depends on thebackground form: • frommultipoledecompositionanalysis • fromdiscretewavelettransform Y. Kalmykov et al., Phys. Rev. Lett. 96 (2006) 012502 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  27. 1- States Level Density in 208Pb | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  28. Photon Strength Function in 208Pb *N.U.H. Syed et al., PRC 79 (2009) 024316 | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  29. Summary and Outlook • Polarized intermediate energy proton scattering at 0°: a new tool to extract complete dipole responce in nuclei • Spinflip / non-spinflip cross section separation • B(E1) strength • Dipole polarizability • Level Densities of 1- states • Photon Strength Function • Extraction of the Bs(M1) strength distribution • Investigation of the dipole strength in 120Sn → Talk A. M. Heilmann HK 50.4 • and 154Sm | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

  30. EPPS0 Collaborators Dep. of Phys., Osaka University Y. Fujita Dep. of Phys., Kyoto University H. Sakaguchi, J. Zenihiro CNS, Univ. of Tokyo Y. Sasamoto IFIC-CSIC, Valencia B. Rubio Univ. of Witwatersrand J. Carter GSI, Darmstadt B. Özel, E. Litvinova • RCNP, Osaka University • T. Adachi, H. Fujita, K. Hatanaka, M. Kato, H. Matsubara, M. Okamura, Y. Sakemi, • Y. Shimizu,Y. Tameshige, A. Tamii, • M. Yosoi • iThembaLABs • R. Neveling, F.D. Smit • Texas A&M University, Commerce, USA • C. Bertulani • IKP, TU Darmstadt • M. Heilmann, Y. Kalmykov, • P. von Neumann-Cosel, • I. Poltoratska, V. Ponomarev, A. Richter, Thank you !! | Institut für Kernphysik | TU Darmstadt | Iryna Poltoratska | Münster 2011

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