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RIKEN Seminar, September 8th, 2011 1 Complete Electric Dipole Response and Neutron Skin in 208 Pb A. Tamii Research Center for Nuclear Physics, Osaka University.

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Presentation on theme: "RIKEN Seminar, September 8th, 2011 1 Complete Electric Dipole Response and Neutron Skin in 208 Pb A. Tamii Research Center for Nuclear Physics, Osaka University."— Presentation transcript:

1 RIKEN Seminar, September 8th, Complete Electric Dipole Response and Neutron Skin in 208 Pb A. Tamii Research Center for Nuclear Physics, Osaka University

2 RIKEN Seminar, September 8th, 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

3 RIKEN Seminar, September 8th, 2011 SnSn SpSp Illustrative View of E1 Response Particle ( neutron ) separation energy 0 PDR GDR g.s. oscillation of neutron skin against core? oscillation between neutrons and protons E1 1 - core neutron skin symmetry energy

4 RIKEN Seminar, September 8th, 2011 Electric Pygmy Dipole Resonance (PDR) PDR: resonance-like structure, typically close to neutron threshold Strength related to neutron excess measure of neutron skin symmetry energy Strength distribution around neutron threshold relevant for nucleosynthesis (r-process) Dipole oscillation between an isospin-saturated core and a neutron (proton) skin?

5 RIKEN Seminar, September 8th, 2011 LAND exp. at GSI dissociation c.s.photo-nuclear c.s. P. Adrich et al., PRL95, (2005) Sn Isotopes

6 RIKEN Seminar, September 8th, Ni O. Wieland et al. PRL102, (2009)

7 RIKEN Seminar, September 8th, 2011 Dipole oscillation between an isospin-saturated core and a neutron (proton) skin? Pigmy Dipole Resonance T. Aumann et al., NPA805, 198c(2008).

8 RIKEN Seminar, September 8th, 2011 J. Zenihiro et al., PRC82, (2010).

9 RIKEN Seminar, September 8th, 2011 J. Zenihiro et al., PRC82, (2010).

10 RIKEN Seminar, September 8th, 2011 SnSn SpSp Illustrative View of E1 Response Particle ( neutron ) separation energy 0 PDR GDR g.s. oscillation of neutron skin against core? oscillation between neutrons and protons E1 1 - core neutron skin symmetry energy

11 RIKEN Seminar, September 8th, 2011 P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, (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 RIKEN Seminar, September 8th, 2011 SnSn SpSp ( ,  ’) ( ,n) Giant Resonances and Continuum Discrete States Illustrative View of E1 Response Particle ( neutron ) separation energy (e,e’), (p,p’) 0 PDR GDR g.s. (Coulomb Excitation) (Coulomb Dissociation) ← Unstable nuclei

13 RIKEN Seminar, September 8th, 2011 SnSn SpSp ( ,  ’) ( ,n) GR and Continuum (Main Strength) Discrete (Small Strength) Illustrative View of E1 Response Particle ( neutron ) separation energy (e,e’), (p,p’) 0 PDR GDR g.s. 208 Pb( ,  ) M1 strength measured by R.M. Laszewski et al, PRL61(1988)1710

14 RIKEN Seminar, September 8th, 2011 p q,q, A A* p’ Coulomb (or Strong) Interaction detector beam  A A* Excited State Target Nucleus real photon Probing EM response of the target nucleus Decay products and/or  -rays are measured. Select a low momentum transfer (q~0) kinematical condition, i.e. at zero degrees Excited State Target Nucleus detector Missing Mass Spectroscopy: Insensitive to the decay channel. Total strengths are measured.

15 RIKEN Seminar, September 8th, 2011 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. Proton Inelastic Scattering

16 RIKEN Seminar, September 8th, 2011 Experimental Method High-Resolution (p,p’) measurement at close to zero degrees AT et al., 

17 RIKEN Seminar, September 8th, 2011 High-resolution Spectrometer Grand Raiden High-resolution WS beam-line (dispersion matching)

18 RIKEN Seminar, September 8th, 2011 Spectrometers in the 0-deg. experiment setup Intensity : 3 ~ 8 nA As a beam spot monitor in the vertical direction Transport : Dispersive mode Polarized Proton Beam at 295 MeV Focal Plane Polarimeter

19 RIKEN Seminar, September 8th, Oct2008-Nov Spin Precession in the Spectrometer  p : precession angle with respect to the beam direction  b : bending angle of the beam g: Lande’s g-factor  : gamma in special relativity

20 RIKEN Seminar, September 8th, 2011

21

22 I. Poltoratska, PhD thesis

23 RIKEN Seminar, September 8th, 2011 I. Poltoratska, PhD thesis

24 RIKEN Seminar, September 8th, 2011 E1/M1 Decomposition by Spin Observables spinflip / non-spinflip separation* (model-independent) Polarization observables at 0° -1 for  S = 1, M1 excitations 3 for  S = 0, E1 excitations E1 and M1 cross sections can be decomposed T. Suzuki, PTP 103 (2000) 859 At 0° D SS = D NN

25 RIKEN Seminar, September 8th, 2011

26

27  S  (p,p’) this work J. Enders et al., NPA724(2003)243 N. Ryezayeva et al.,  PRL27(2002) A. Veyssiere et al., NPA159(1970)561 Z.W.Bell et al., PRC25(1982)791 Preliminary ΔS=0 (~E1)

28 RIKEN Seminar, September 8th, 2011 Multipole Decomposition Neglect of data for  >4: (p,p´) response too complex Included E1/M1/E2 or E1/M1/E3 (little difference)

29 RIKEN Seminar, September 8th, 2011 Comparison of Both Methods Total  S = 1  S = 0

30 RIKEN Seminar, September 8th, 2011 I. Poltoratska, PhD thesis

31 RIKEN Seminar, September 8th, 2011 I. Poltoratska, PhD thesis

32 RIKEN Seminar, September 8th, 2011 E1 Response in 208 Pb Quasiparticle Phonon Model 3 phonons up to 8.2 MeV 2 phonons in the GDR region V.Yu. Ponomarev Relativistic Quasiparticle Time-Blocking Approximation 2QP×1 phonon E. Litvinova et al., PRC 78 (2008) , PRC 79 (2009) This Exp.

33 RIKEN Seminar, September 8th, 2011 I. Poltoratska, PhD thesis Relativistic Quasiparticle Time Blocking Approximation Quasiparticle Phonon Model up to 130 MeV fm 3 /e 2

34 RIKEN Seminar, September 8th, 2011 Self-Consistent Mean Field Theory (Nuclear) Energy Density Functional Theory Skyrm Force: SV-min P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, (R) (2010). - SV-min parameters were determined to reproduce binding energies, diffraction radii, surface thickness, r.m.s. radii, pairing gap, and ls-splitting.

35 RIKEN Seminar, September 8th, 2011 AT, I. Poltoratsuka, et al., PRL107, (2011) [8] P.-G. Reinhard and W. Nazarewicz, PRC81, (R) (2010) fm fm 3 /e 2

36 RIKEN Seminar, September 8th, 2011 P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, (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.

37 RIKEN Seminar, September 8th, 2011 J. Zenihiro et al., PRC82, (2010). proton elastic scattering fm fm (p,p’) with EDF SkM* Antiproton Atoms fm PREX fm J. Zenihiro et al., PRC82, (2010).

38 RIKEN Seminar, September 8th, 2011 spin-M1 Strength Distribution in 208 Pb

39 RIKEN Seminar, September 8th, 2011 M. Sasano et al., PRC79, (2009). Gamow-Teller unit cross section of (p,n) reactions at 297 MeV, extrapolated to A=208: Converted to B(  ) unit cross section of (p,p’) reactions for A=208. Extraction of spin-M1 strengh (  After making extrapolation to q=0, with a help of DWBA calc.

40 RIKEN Seminar, September 8th, 2011

41 Preliminary

42 RIKEN Seminar, September 8th, 2011 Summary High-resolution (p,p’) measurement (inc. pol-transfer data) at forward angles has been applied for extracting E1 response in 208 Pb. 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 fm 3 /e 2. 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 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. 120 Sn, 154 Sm (dcs and spin), 88 Mo, 90 Zr, 92 Mo (dcs) : under analysis

43 RIKEN Seminar, September 8th, 2011 END


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