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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. - PowerPoint PPT Presentation
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RIKEN Seminar, September 8th, 2011
1
Complete Electric Dipole Responseand Neutron Skin in 208Pb
A. TamiiResearch Center for Nuclear Physics, Osaka University
RIKEN Seminar, September 8th, 2011
2
Collaborators RCNP, Osaka UniversityA. Tamii, H. Matsubara, H. Fujita, K. Hatanaka,
H. Sakaguchi Y. Tameshige, M. Yosoi and J. Zenihiro
Dep. of Phys., Osaka UniversityY. Fujita
Dep. of Phys., Kyoto UniversityT. Kawabata
CNS, Univ. of TokyoK. Nakanishi,
Y. Shimizu and Y. Sasamoto
CYRIC, Tohoku UniversityM. Itoh and Y. Sakemi
Dep. of Phys., Kyushu UniversityM. Dozono
Dep. of Phys., Niigata UniversityY. Shimbara
IKP, TU-DarmstadtP. von Neumann-Cosel, A-M. Heilmann,
Y. Kalmykov, I. Poltoratska, V.Yu. Ponomarev,
A. Richter and J. Wambach
KVI, Univ. of GroningenT. Adachi and L.A. Popescu
IFIC-CSIC, Univ. of ValenciaB. Rubio and A.B. Perez-Cerdan
Sch. of Science Univ. of WitwatersrandJ. Carter and H. Fujita
iThemba LABSF.D. Smit
Texas A&M CommerceC.A. Bertulani
GSIE. Litivinova
RIKEN Seminar, September 8th, 2011
Sn Sp
Illustrative View of E1 ResponseParticle ( neutron ( separation energy
0
PDR GDRg.s.
oscillation of neutron skin against core?
oscillation between neutrons and protons
E1
1-
core neutron skin
symmetry energy
RIKEN Seminar, September 8th, 2011
Electric Pygmy Dipole Resonance (PDR)
PDR: resonance-like structure, typically close to neutron threshold
Strength related to neutron excessmeasure 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?
RIKEN Seminar, September 8th, 2011
LAND exp. at GSI
dissociation c.s. photo-nuclear c.s.
P. Adrich et al., PRL95, 132501(2005)
Sn Isotopes
RIKEN Seminar, September 8th, 2011
68NiO. Wieland et al. PRL102, 092502(2009)
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).
RIKEN Seminar, September 8th, 2011
J. Zenihiro et al., PRC82, 044611 (2010).
RIKEN Seminar, September 8th, 2011
J. Zenihiro et al., PRC82, 044611 (2010).
RIKEN Seminar, September 8th, 2011
Sn Sp
Illustrative View of E1 ResponseParticle ( neutron ( separation energy
0
PDR GDRg.s.
oscillation of neutron skin against core?
oscillation between neutrons and protons
E1
1-
core neutron skin
symmetry energy
RIKEN Seminar, September 8th, 2011
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.
RIKEN Seminar, September 8th, 2011
Sn Sp
(,’)
(,n)
Giant Resonances and ContinuumDiscrete States
Illustrative View of E1 ResponseParticle ( neutron ( separation energy
(e,e’), (p,p’)
0
PDR GDRg.s.
(Coulomb Excitation) (Coulomb Dissociation) ← Unstable nuclei
RIKEN Seminar, September 8th, 2011
Sn Sp
(,’)
(,n)
GR and Continuum (Main Strength)Discrete (Small Strength)
Illustrative View of E1 ResponseParticle ( neutron ( separation energy
(e,e’), (p,p’)
0
PDR GDRg.s.
208Pb(,)M1 strength measured by
R.M. Laszewski et al, PRL61(1988)1710
RIKEN Seminar, September 8th, 2011
p
q,
A A*
p’
Coulomb (or Strong) Interaction
detector
beam
A A*
Excited StateTarget 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 StateTarget Nucleus
detector
detector
Missing Mass Spectroscopy: Insensitive to the decay channel. Total strengths are measured.
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
RIKEN Seminar, September 8th, 2011
Experimental Method
High-Resolution (p,p’) measurement at close to zero degrees
AT et al.,
RIKEN Seminar, September 8th, 2011
High-resolution Spectrometer
Grand Raiden
High-resolution WS beam-line(dispersion matching)
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
RIKEN Seminar, September 8th, 2011
2006-Oct 2008-Nov
Spin Precession in the Spectrometer
bp
g )12
( p: precession angle with respect to the beam directionb: bending angle of the beamg: Lande’s g-factor: gamma in special relativity
162b 180b
RIKEN Seminar, September 8th, 2011
RIKEN Seminar, September 8th, 2011
RIKEN Seminar, September 8th, 2011
I. Poltoratska, PhD thesis
RIKEN Seminar, September 8th, 2011
I. Poltoratska, PhD thesis
RIKEN Seminar, September 8th, 2011
E1/M1 Decomposition by Spin Observables
LLNNSS DDD
spinflip / non-spinflip separation*
(model-independent)
Polarization observables at 0°
-1 for S = 1, M1 excitations
3 for S = 0, E1 excitations
0ΔS
1ΔS
for
for
0
1TransferSpinTotal
4
)2(3
LLSS DD
E1 and M1 cross sections can be decomposed
T. Suzuki, PTP 103 (2000) 859
At 0° DSS = DNN
RIKEN Seminar, September 8th, 2011
RIKEN Seminar, September 8th, 2011
RIKEN Seminar, September 8th, 2011
S
(p,p’) this work
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
Preliminary
ΔS=0 (~E1)
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)
RIKEN Seminar, September 8th, 2011
Comparison of Both Methods
Total
S = 1
S = 0
RIKEN Seminar, September 8th, 2011
I. Poltoratska, PhD thesis
RIKEN Seminar, September 8th, 2011
I. Poltoratska, PhD thesis
RIKEN Seminar, September 8th, 2011
E1 Response in 208Pb
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
This Exp.
RIKEN Seminar, September 8th, 2011
I. Poltoratska, PhD thesis
Relativistic Quasiparticle Time Blocking Approximation
Quasiparticle Phonon Model
up to 130 MeV20.1+-0.6 fm3/e2
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, 051303(R) (2010).
- SV-min parameters were determined to reproduce binding energies, diffraction radii, surface thickness, r.m.s. radii, pairing gap, and ls-splitting.
RIKEN Seminar, September 8th, 2011
AT, I. Poltoratsuka, et al., PRL107, 062502(2011)
[8] P.-G. Reinhard and W. Nazarewicz, PRC81, 051303(R) (2010).
0.156+0.025-0.021 fm
20.1+-0.6 fm3/e2
RIKEN Seminar, September 8th, 2011
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.
RIKEN Seminar, September 8th, 2011
J. Zenihiro et al., PRC82, 044611 (2010).
proton elastic scattering 0.211+0.054-0.063 fm
0.156+0.025-0.021 fm
(p,p’) with EDF SkM*
Antiproton Atoms0.18+-0.02 fm
PREX 0.34+0.15-0.17 fm
J. Zenihiro et al., PRC82, 044611 (2010).
RIKEN Seminar, September 8th, 2011
spin-M1 Strength Distribution in 208Pb
RIKEN Seminar, September 8th, 2011
M. Sasano et al., PRC79, 024602(2009).
mb/sr9.1208ˆGT A
2Nmb/sr/72.0208ˆ A
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.
RIKEN Seminar, September 8th, 2011
RIKEN Seminar, September 8th, 2011
Preliminary
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 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
RIKEN Seminar, September 8th, 2011
END