Atsushi Tamii Research Center for Nuclear Physics (RCNP) Osaka - PowerPoint PPT Presentation

Electric Dipole Response of Nuclei 
 Studied by Proton Inelastic Scattering Atsushi Tamii Research Center for Nuclear Physics (RCNP) 
 Osaka University, Japan photos 
 in Osaka U. 
 2015.10.31 High Resolution Spectroscopy and Tensor Interactions 
 November 16-19, 2015 � 1 at Nakanoshima Center, Osaka University


 
 1. Electric Dipole Responses 
 RCNP, TU-Darmstadt, Konan, … AT et al., PRL 107 , 062502 (2011) 
 C. Iwamoto et al., PRL 108 , 262501 (2012) 
 Symmetry Energy 
 I. Poltoratska et al., PRC 85 , 041304 (2012) 
 AT et al., EPJA 50 , 28 (2014) 
 Electric Dipole Polarizability 
 A.M. Krumbholz et al., PLB 744 , 7 (2015) 
 Neutron Skin 
 T. Hashimoto et al ., PRC 92 , 031305(R)(2015) Pygmy Dipole Resonance 
 Zr Isotopes: Talk by C. Iwamoto RCNP, TU-Darmstadt, … 2. Spin-M1 Responses 
 H. Matsubara et al., PRL 115 , 102501 (2015) Quenching of IS/IV Spin-M1 Strengths 
 Talk by H. Matsubara

RCNP-282 Collaboration 208 Pb 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 IKP, TU-Darmstadt Y. Fujita P. von Neumann-Cosel , A-M. Heilmann, 
 � Y. Kalmykov, I. Poltoratska , V.Yu. Ponomarev, 
 Dep. of Phys., Kyoto University A. Richter and J. Wambach 
 T. Kawabata � KVI, Univ. of Groningen CNS, Univ. of Tokyo T. Adachi and L.A. Popescu K. Nakanishi, 
 IFIC-CSIC, Univ. of Valencia Y. Shimizu and Y. Sasamoto B. Rubio and A.B. Perez-Cerdan � Sch. of Science Univ. of Witwatersrand CYRIC, Tohoku University J. Carter and H. Fujita M. Itoh and Y. Sakemi iThemba LABS � F.D. Smit Dep. of Phys., Kyushu University Texas A&M Commerce M. Dozono C.A. Bertulani Dep. of Phys., Niigata University GSI Y. Shimbara E. Litivinova 33

Symmetry Energy of Nuclear EOS 
 is important in nuclear physics and nuclear-astrophysics Neutron star mass vs radius Core-collapse supernova Y. Suwa et al., ApJ764, 99 (2013). Nucleosynthesis Lattimer et al., Phys. Rep. 442, 109(2007) Langanke and Martinez-Pinedo Neutron star structure Neutron star cooling A ccreting neutron star 
 X-ray burst http://www.astro.umd.edu/~miller/nstar.html Lattimer and Prakash, Science 304, 536 (2004).

Nuclear Equation of State (EOS) 
 at zero temperature ( ) ( ) ( ) r r r ρ = ρ + ρ n p EOS for Energy per nucleon ( ) r ( ) r E E ρ − ρ n p 2 + ( ) r ( ) ( ) ( ) δ = , , 0 S ... ρ δ = ρ + ρ δ ( ) ( ) r r ρ + ρ A A n p : Symmetry energy ρ Saturation Density ~0.16 fm -3 0 K L sym 2 ( ) ( ) ( ) S J ... ρ = + ρ − ρ + ρ − ρ + 0 0 2 3 18 ρ ρ 0 0 S: symmetry energy at the saturation density 
 L (slope parameter): density dependence 4 L P R ∝ ∝ Determination of the symmetry energy parameters 
 n − star especially L is becoming important. (Baryonic Pressure)

核子当たりのエネルギー Nuclear Equation of State (EOS) Steiner et al., Phys. Rep. 411 325(2005) Neutron Matter ( δ =1) ∝ L E/N (MeV) E/A (MeV) Neutron matter 
 ( δ =1) ~J Nuclear matter ( δ =0) Neutron Density (fm -3 ) Nucleon Density (fm -3 ) ( ) δ 2 + … E ) = E ( ( ) + S ρ Saturation Density ρ 0 A ρ , δ A ρ ,0 ( ) = ρ n r ( ) + ρ p r ( ) ρ r ( ) − δ p r ( ) ( ) = δ n r 2 + … δ r ) + K sym ( ) = J + L ( ( ) ( ) + δ p r ( ) S ρ ρ − ρ 0 2 ρ − ρ 0 δ n r 3 ρ 0 18 ρ 0 : ρ Saturation Density ~0.16 fm -3 0

Correlation Between the Dipole Polarizability ( α D ) 
 and L (and the neutron skin thickness) P.-G. Reinhard and W. Nazarewicz, PRC 81, 051303(R) (2010). Strong correlation between the 
 dipole polarizability and the 
 neutron skin of 208 Pb ~L ! " ! " ( α D ) = α D E P X. Roca-Maza et al ., PRC 88 , 024316(2013) 208 Pb

Electric Dipole Polarizability ( α D ) α D ! " ! " = α NE P Restoring force ← symmetry energy α : dipole polarizability of an atom Inversely energy weighted sum-rule of B(E1) ( ) σ abs ω 2 d ω = 8 π α D = ! c E 1 dB E 1 ∫ ∫ Requires the B ( E1 ) 2 π 2 ω distribution 9

Electric Dipole Response of Nuclei oscillation between oscillation of neutron B ( E1 ) neutrons and protons skin against core? 1 - Low-Lying 
 core Dipole Strength neutron skin (PDR) GDR g.s. 0 S n S p

Electric Dipole Response of Nuclei neutron separation energy NRF B(E1) ( γ ,xn) ( γ , γ ’) (p,p’) Low-lying E1 
 IVGDR ( PDR) 0 g.s. S n S p

Probing the EM response of the target nucleus Real Photon Measurements, NRF or ( γ ,xn) detector Decay γ or n is detected. γ γ ( or xn ) A A * A ( or A- x ) Missing Mass Spectroscopy with Virtual Photon Only the excitation part is probed. 
 Scattered p is detected. → total strengths independent of the decay channel detector p Select q ~0 (~0 deg.) p Coulomb excitation dominates virtual photon EM Interaction is well known 
 * A A (model independent)

Experimental Method High-resolution measurements of proton inelastic scattering 
 at zero degrees and forward angles

Research Center for Nuclear Physics (RCNP), Osaka University Polarized p beam at 295 MeV High-resolution 
 WS beam-line 
 (dispersion matching) High-resolution Spectrometer Grand Raiden

RCNP Ring Cyclotron High quality beams at 100-400 MeV/A

Large Angle Spectromete Grand Raiden Spectrometer

Δ E=20-30 keV ( 3 He,t) at 420 MeV 
 (p,p’) at 300 MeV Dispersion Matching Technique Δ E=80-120 keV

Spectrometers in the 0-deg. experiment setup at RCNP, Osaka AT et al., NIMA605, 326 (2009) As a beam spot monitor in the vertical direction Focal Plane Polarimeter 208 Pb target: 5.2 mg/cm 2 Dispersion Matching Intensity : 1-8 nA Polarized Proton Beam at 295 MeV

B(E1): continuum and GDR region Method 1: Multipole Decomposition Neglect of data for Θ >4: (p,p´) response too complex Included E1/M1/E2 or E1/M1/E3 (little difference) Grazing Angle = 3.0 deg

B(E1): continuum and GDR region Method 2: Decomposition by Spin Observables Polarization observables at 0° spinflip / non-spinflip separation model-independent E1 / spin-M1 decomposition T. Suzuki, PTP 103 (2000) 859 3 ( 2 D D ) spin- M1 1 for Δ S 1 − + # = SS LL Total Spin Transfer Σ ≡ = " 4 0 for Δ S 0 E1 = !

Comparison between the two methods Total Δ S = 1 Δ S = 0

Distribution of B(E1) I. Poltoratska, PhD thesis low-lying discrete states GDR region Excellent agreement between (p,p’) and ( γ , γ ’) below ~ S n

E1 Response of 208 Pb and α D combined data The dipole polarizability of 208 Pb has been precisely determined. AT et al., PRL107, 062502(2011)

Electric Dipole Response of 208 Pb Low-lying Dipole Strength 
 Giant Dipole Resonance (Pygmy Dipole Resonance) Dipole Polarizability (fm 3 ) 20"# 15"# 10"# 5"# Integrated 0"# 5" 10" 15" 20" Excitation Energy (MeV)

Electric Dipole Response of 208 Pb Low-lying Dipole Strength 
 Giant Dipole Resonance (Pygmy Dipole Resonance) alpha_D'in'208PbA α D in 208 Pb Dipole'Polarizability'alpha_D'(fm^3) � Dipole Polarizability α D (fm 3 ) 20.0#$ Dipole Polarizability (fm 3 ) 20"# DP is saturating at around ~40 MeV. 15.0#$ 15"# 10"# 10.0#$ 5"# Integrated 5.0#$ 0"# 5" 10" 15" 20" 0.0#$ 0.0## 20.0## 40.0## 60.0## 80.0## 100.0## 120.0## Excitation Energy (MeV) Excitation'Energy'(MeV) �

Energy Weighted (TRK) Sum-Rule of 208 Pb E10EWSR'in'208Pb 7 1.8#$ Energy'Weighted'Sum0Rule'(TRK'unit) 7 1.6#$ 1.4#$ 1.2#$ 1.0#$ 0.8#$ 0.6#$ 0.4#$ 0.2#$ 0.0#$ 0.0## 20.0## 40.0## 60.0## 80.0## 100.0## 120.0## Excitation'Energy'(MeV) �

Constraints X. Roca-Maza et al . PRC88, 024316 (2013) Symmetry Energy Parameters Neutron Skin Thickness Δ r np = 0 .165 ± (0 .009) expt 
 Experimental Value = α D ± (0 .013) theor ± (0 .021) est fm Constraint in the J - L plane for the estimated J =31 ± (2) est

Constraints on J and L AT et al., EPJA 50 , 28 (2014). M.B. Tsang et al. , PRC 86 , 015803 (2012) C.J. Horowitz et al., JPG41, 093001 (2014) DP: Dipole Polarizability 
 HIC: Heavy Ion Collision 
 PDR: Pygmy Dipole Resonance 
 IAS: Isobaric Analogue State 
 FRDM: Finite Range Droplet 
 Model (nuclear mass analysis) 
 n-star: Neutron Star Observation 
 χ EFT: Chiral Effective Field Theory 
 QMC: S. Gandolfi, EPJA50, 10(2014). QMC I. Tews et al., PRL110, 032504 (2013)

Neutron Skin Thickness of 208 Pb Δ R np = 0 .165 ± (0 .009) expt ± (0 .013) theor ± (0 .021) est fm for the estimated J =31 ± (2) est X. Roca-Maza et al ., PRC 88 , 024316(2013)

Dipole Polarizability of 120 Sn T. Hashimoto et al ., PRC 92 , 031305(R)(2015). (p, p’) ( γ , n) ( γ , xn) ( γ , xn) 135 MeV α D (fm 3 ) 1.12 ± 0.07 7.00 ± 0.29 0.82 ± 0.12 Total: α D = 8.93 ± 0.36 fm 3

Constraints on J-L and n-skin thickness from DP Data X. Roca-Maza et al., submitted to PRC Data 208 Pb: AT et al ., PRL 107 , 062502 (2011). RCNP 120 Sn: T. Hashimoto et al ., PRC 92 , 031305(R)(2015). RCNP 68 Ni: D.M. Rossi et al ., PRL 111 , 242503 (2013). GSI 120 Sn 68 Ni