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Complete Electric Dipole Response and Neutron Skin in 208 Pb

Complete Electric Dipole Response and Neutron Skin in 208 Pb. A. Tamii Research Center for Nuclear Physics, Osaka University. Collaborators. RCNP, Osaka University A. Tamii , H. Matsubara, H. Fujita, K. Hatanaka, H. Sakaguchi Y. Tameshige, M. Yosoi and J. Zenihiro.

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Complete Electric Dipole Response and Neutron Skin in 208 Pb

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  1. Complete Electric Dipole Responseand Neutron Skin in 208Pb A. Tamii Research Center for Nuclear Physics, Osaka University

  2. Collaborators RCNP, Osaka University A. Tamii, H. Matsubara, H. Fujita, K. Hatanaka, H. Sakaguchi Y. Tameshige, M. Yosoi and J. Zenihiro Dep. of Phys., Osaka University Y. Fujita Dep. of Phys., Kyoto University T. Kawabata CNS, Univ. of Tokyo K. Nakanishi, Y. Shimizu and Y. Sasamoto CYRIC, Tohoku University M. Itoh and Y. Sakemi Dep. of Phys., Kyushu University M. Dozono Dep. of Phys., Niigata University Y. Shimbara IKP, TU-Darmstadt P. von Neumann-Cosel, A-M. Heilmann, Y. Kalmykov, I. Poltoratska, V.Yu. Ponomarev,A. Richter and J. Wambach KVI, Univ. of Groningen T. Adachi and L.A. Popescu IFIC-CSIC, Univ. of Valencia B. Rubio and A.B. Perez-Cerdan Sch. of Science Univ. of Witwatersrand J. Carter and H. Fujita iThemba LABS F.D. Smit Texas A&M Commerce C.A. Bertulani GSI E. Litivinova 2

  3. Illustrative View of E1 Response Particle （neutron） separation energy E1 1- oscillation between neutrons and protons oscillation of neutron skin against core? symmetry energy core neutron skin GDR PDR g.s. 0 Sn Sp

  4. Electric Pygmy Dipole Resonance (PDR) • PDR: resonance-like structure, typically close to neutron threshold • Strength related to neutron excess • measure of neutron skinsymmetry energy • Strength distribution around neutron threshold relevant fornucleosynthesis (r-process) Dipole oscillation between an isospin-saturated core and a neutron (proton) skin?

  5. Sn Isotopes LAND exp. at GSI dissociation c.s. photo-nuclearc.s. P. Adrich et al., PRL95, 132501(2005)

  6. 68Ni O. Wieland et al. PRL102, 092502(2009)

  7. Pigmy Dipole Resonance Dipole oscillation between an isospin-saturated core and a neutron (proton) skin? T. Aumann et al., NPA805, 198c(2008).

  8. J. Zenihiro et al., PRC82, 044611 (2010).

  9. J. Zenihiro et al., PRC82, 044611 (2010).

  10. Illustrative View of E1 Response Particle （neutron） separation energy E1 1- oscillation between neutrons and protons oscillation of neutron skin against core? symmetry energy core neutron skin GDR PDR g.s. 0 Sn Sp

  11. P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, 051303(R) (2010). Self-consistent mean field theory in the energy density functional theory formulationn with SV-min interaction.- SV-min parameters were determined to reproduce binding energies, r.m.s. radii, pairing gap, ls-splitting, surface thickness, etc.

  12. Illustrative View of E1 Response Particle （neutron） separation energy Giant Resonances and Continuum Discrete States (Coulomb Dissociation) (Coulomb Excitation) ← Unstable nuclei (g,n) (g,g’) (e,e’), (p,p’) GDR PDR g.s. 0 Sn Sp

  13. M1 strength measured by 208Pb(g,g) R.M. Laszewski et al, PRL61(1988)1710 Illustrative View of E1 Response Particle （neutron） separation energy GR and Continuum(Main Strength) Discrete (Small Strength) (g,n) (g,g’) (e,e’), (p,p’) GDR PDR g.s. 0 Sn Sp

  14. Probing EM response of the target nucleus g detector real photon detector A* A Decay products and/or g-rays are measured. Excited State Target Nucleus Missing Mass Spectroscopy:Insensitive to the decay channel. Total strengths are measured. detector p’ Select a low momentum transfer (q~0) kinematical condition,i.e. at zero degrees beam p Coulomb (or Strong) Interaction q,w A* A Excited State Target Nucleus

  15. Proton Inelastic Scattering Missing Mass Measurement - independent to the decay property of the excited states and decay threshold.- no feeding from upper excited states- measure of the total (not partial) width At 0 deg, E1 excitation in dominated by Coulomb interaction and M1 by nuclear interaction High-resolution (~20keV). High and uniform detection efficiency. Single shot measurement in an excitation energy region of 5-25MeV. Uncertainty from reaction mechanism. Nuclear interaction and coulomb interaction. Polarization transfer and angular distribution of the C.S. can be used for E1/M1 decomposition.

  16. Experimental MethodHigh-Resolution (p,p’) measurement at close to zero degrees AT et al., NIM A605, 326 (2009)

  17. High-resolution WS beam-line(dispersion matching) High-resolution Spectrometer Grand Raiden

  18. Spectrometers in the 0-deg. experiment setup As a beam spot monitor in the vertical direction Focal Plane Polarimeter Transport : Dispersive mode Intensity : 3 ~ 8 nA Polarized Proton Beam at 295 MeV

  19. Spin Precession in the Spectrometer qp: precession angle with respect to the beam directionqb: bending angle of the beamg: Lande’s g-factorg: gamma in special relativity 2006-Oct 2008-Nov

  20. I. Poltoratska, PhD thesis

  21. I. Poltoratska, PhD thesis

  22. E1/M1 Decomposition by Spin Observables Polarization observables at 0° spinflip / non-spinflip separation* (model-independent) -1 for DS = 1, M1 excitations 3 for DS = 0, E1 excitations E1 and M1 cross sections can be decomposed At 0° DSS = DNN T. Suzuki, PTP 103 (2000) 859

  23. Preliminary (DS=0) (p,p’) this work ΔS=0 (~E1) J. Enders et al., NPA724(2003)243N. Ryezayeva et al.,PRL27(2002)272502A. Veyssiere et al., NPA159(1970)561Z.W.Bell et al., PRC25(1982)791

  24. Multipole Decomposition • Neglect of data for Q>4: (p,p´) response too complex • Included E1/M1/E2 or E1/M1/E3 (little difference)

  25. Comparison of Both Methods Total DS = 1 DS = 0

  26. I. Poltoratska, PhD thesis

  27. I. Poltoratska, PhD thesis

  28. E1 Response in 208Pb This Exp. Quasiparticle Phonon Model3 phonons up to 8.2 MeV2 phonons in the GDR regionV.Yu. Ponomarev Relativistic Quasiparticle Time-Blocking Approximation2QP×1 phononE. Litvinova et al., PRC 78 (2008) 014312, PRC 79 (2009) 054312

  29. up to 130 MeV20.1+-0.6 fm3/e2 Quasiparticle Phonon Model Relativistic Quasiparticle Time Blocking Approximation I. Poltoratska, PhD thesis

  30. P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, 051303(R) (2010). Self-Consistent Mean Field Theory (Nuclear) Energy Density Functional Theory Skyrm Force: SV-min - SV-min parameters were determined to reproduce binding energies, diffraction radii, surface thickness, r.m.s. radii, pairing gap, and ls-splitting.

  31. 20.1+-0.6 fm3/e2 0.156+0.025-0.021 fm [8] P.-G. Reinhard and W. Nazarewicz, PRC81, 051303(R) (2010). AT, I. Poltoratsuka, et al., PRL107, 062502(2011)

  32. P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, 051303(R) (2010). Self-consistent mean field theory in the energy density functional theory formulationn with SV-min interaction.- SV-min parameters were determined to reproduce binding energies, r.m.s. radii, pairing gap, ls-splitting, surface thickness, etc.

  33. (p,p’) with EDF SkM* J. Zenihiro et al., PRC82, 044611 (2010). 0.156+0.025-0.021 fm PREX 0.34+0.15-0.17 fm proton elastic scattering 0.211+0.054-0.063 fm J. Zenihiro et al., PRC82, 044611 (2010). Antiproton Atoms0.18+-0.02 fm

  34. spin-M1 Strength Distribution in 208Pb

  35. Extraction of spin-M1 strengh (B(s)) After making extrapolation to q=0, with a help of DWBA calc. M. Sasano et al., PRC79, 024602(2009). Gamow-Teller unit cross section of (p,n) reactions at 297 MeV, extrapolated to A=208: Converted to B(s) unit cross section of (p,p’) reactions for A=208.

  36. Preliminary

  37. Summary • High-resolution (p,p’) measurement (inc. pol-transfer data) at forward angles has been applied for extracting E1 response in 208Pb. • Special interest is placed on the E1/spin-M1 strength distribution in the region of neutron separation energy. • Agreement on E1/spin-M1 decomposition is quite satisfactory between the two methods using spin-transfer and multipole-decomposition. • The overall E1 response in 208Pb has been accurately determined. • The electric-dipole polarizability of 208Pb has been determined as 20.1+-0.6 fm3/e2. The polarizability is discussed to be sensitive to the neutron skin and nuclear symmetry energy. • Refering a self consistent mean field calculation by P.-G. Reinhard and W. Nazarewicz, the polarizability corresponds to the neutron-skin thickness of 0.156+0.025-0.021 fm, although the number is model-dependent. • With independent determination of the neutron-skin thickness, the electric dipole polarizability will much constrain the model parameters. PDR strength is also discussed to be sensitive to the neutron skin thickness. • 120Sn, 154Sm (dcs and spin), 88Mo, 90Zr, 92Mo (dcs) : under analysis

  38. END

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