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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. Motivation Experimental setup Results - Coulomb excitation - Multipole decomposition - Asymmetry

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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 • Motivation • Experimental setup • Results - Coulomb excitation - Multipole decomposition - Asymmetry • Summary and outlook

  2. B(E1) Strength Distribution 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 2

  3. ReminderThe Pygmy Dipole Resonance in 208Pb • Excellent agreement with QPM N. Ryezayeva et al., PRL 89 (2002) 272502 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 3

  4. Structure of Low-energy E1 Modes • Oscillations of neutron skin • Toroidal mode 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 4

  5. Elucidation of the Structure of the Low-Energy Modes • (e,e´) at backward angles - transverse response S-DALINAC,TU Darmstadt • (p,p´) at 0° - longitudinal response (Coulomb excitation) - sensitive to polarization observables RCNP,Osaka University 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 5

  6. Spin M1 Strength in 208Pb • Spin-flip M1 resonance is quenched -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° gselectivity on DL=0 transitions - isovector spin-flip M1 transitions enhanced • Overlap with PDR 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 6

  7. -1 for DS = 1, M1 excitations 3 for DS = 0, E1 excitations Polarized Proton Scattering 300 MeV optimal • spin-isospin excitations • intermediate energy • angular distributions • E1 / M1 separation - selectivity on DL = 0 - Coulomb excitation - measurements at 0° Multipole Decomposition - measurements at finite angles - Coulomb-nuclear interference • polarization observables at 0° • spinflip / non-spinflip separation • high resolution measurements needed 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 7

  8. Cyclotron Facility at RCNP Ring Cyclotron AVF HIPIS 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 8

  9. 0o Setup at RCNP 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 9

  10. Focal Plane Detectors Measured polarization observables: Ay - asymmetry DSS = DNN at 0° - sideway polarization transfer coefficient DLL at 0° - longitudinal polarization transfer coefficient 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 10

  11. Measured Spectrum • mildly under-focusing mode in non-dispersive direction • flat distribution of the background on the Y focal plane • determines shape and magnitude of the background 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 11

  12. Measured SpectrumBackground-Subtracted Spectrum • Pronounced fine structure of the GDR is recognized • Strong Coulomb excitation of the GDR at 0° 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 12

  13. Measured SpectrumLow-Energy Part • All dipole transitions known from (g,g´) are observed 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 13

  14. Coulomb Excitation of E1 Transitions *C.A. Bertulani et al., Comp. Phys. Comm. 152 (2003) 317 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 14

  15. Extracted Transition Strengths 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 15

  16. Spectra at Finite Angles 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 16

  17. Multipole Decomposition • Restrict angular distribution to 2.5° setting • DL = 0 - theoretical ds/dW for IS and IV excitations are similar • DL = 1 - angular distribution averaged over individual levels • DL = 2 - substitute for all DL > 1 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 17

  18. Experimental Asymmetry 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 18

  19. Experimental AsymmetryLow-Energy Part 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 19

  20. Summary and Outlook • First high-resolution zero degree polarized proton scattering experiment on 208Pb performed • Measured observables: ds/dW, Ay, DSS, DLL • Selective Coulomb excitation of 1- states at very forward angles observed • Multipole decomposition analysis • Analysis of the polarization observables • Investigation of the dipole strength in 120Sn 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 20

  21. Pygmy Dipole Resonance in 120SnMeasured Spectra A. M. Heilmann, Poster, HK 67.6 B. Özel et al., PLB, submitted 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 21

  22. Pygmy Dipole Resonance in 120SnMeasured Spectra II 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 22

  23. 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 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, Commerece, USA C. Bertulani IKP, TU Darmstadt O. Burda, A. M. Heilmann Y. Kalmykov, P. von Neumann-Cosel, A. Richter, I. Poltoratska, V. Ponomarev Thank you !! 9/24/2014 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 23

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