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

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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 at Nakanoshima Center, Osaka University

• 1. Electric Dipole Responses



 Symmetry Energy
 Electric Dipole Polarizability
 Neutron Skin
 Pygmy Dipole Resonance


• 2. Spin-M1 Responses



 Quenching of IS/IV Spin-M1 Strengths


AT et al., PRL107, 062502 (2011)


• C. Iwamoto et al., PRL108, 262501 (2012)

• I. Poltoratska et al., PRC85, 041304 (2012)


AT et al., EPJA50, 28 (2014)
 A.M. Krumbholz et al., PLB744, 7 (2015)


• T. Hashimoto et al., PRC92, 031305(R)(2015)
• H. Matsubara et al., PRL115, 102501 (2015)

RCNP, TU-Darmstadt, Konan, … RCNP, TU-Darmstadt, … Talk by H. Matsubara Zr Isotopes: Talk by C. Iwamoto

33

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

208Pb

RCNP-282 Collaboration

Symmetry Energy of Nuclear EOS


is important in nuclear physics and nuclear-astrophysics

Lattimer et al., Phys. Rep. 442, 109(2007)

Accreting neutron star


X-ray burst Neutron star mass vs radius Neutron star structure Core-collapse supernova Neutron star cooling Nucleosynthesis

http://www.astro.umd.edu/~miller/nstar.html Langanke and Martinez-Pinedo

• Y. Suwa et al., ApJ764, 99 (2013).

Lattimer and Prakash, Science 304, 536 (2004).

Nuclear Equation of State (EOS)


at zero temperature

( ) ( ) ( ) ( ) ( )

r r r r r

p n p n

ρ ρ ρ ρ δ + − =

( ) ( ) ( )

r r r

p n

ρ ρ ρ + = Determination of the symmetry energy parameters
 especially L is becoming important.

( ) ( ) ( )

... , ,

2 +

+ = δ ρ ρ δ ρ S A E A E

( ) ( ) ( )

... 18 3

2 2

+ − + − + = ρ ρ ρ ρ ρ ρ ρ

sym

K L J S

Symmetry energy

S: symmetry energy at the saturation density


L (slope parameter): density dependence EOS for Energy per nucleon : ρ

Saturation Density ~0.16 fm-3

4 star n−

∝ ∝ R P L

(Baryonic Pressure)

Steiner et al., Phys. Rep. 411 325(2005)

核子当たりのエネルギー

Nucleon Density (fm-3) E/A (MeV) E/N (MeV)

Nuclear Equation of State (EOS)

Neutron Matter (δ=1) Neutron matter 
 (δ=1) Nuclear matter (δ=0)

Neutron Density (fm-3)

~J ∝L

Saturation Density ρ0

E A ρ,δ

( ) = E

A ρ,0

( )+ S ρ ( )δ 2 +…

S ρ

( ) = J + L

3ρ0 ρ − ρ0

( )+ Ksym

18ρ0

2 ρ − ρ0

( )

2 +…

: ρ

Saturation Density ~0.16 fm-3

ρ r

( ) = ρn r ( )+ ρ p r ( )

δ r

( ) = δ n r ( )−δ p r ( )

δ n r

( )+δ p r ( )

P.-G. Reinhard and W. Nazarewicz, PRC 81, 051303(R) (2010).

Correlation Between the Dipole Polarizability (αD)
 and L (and the neutron skin thickness)

Strong correlation between the 
 dipole polarizability and the 
 neutron skin of 208Pb

208Pb

• X. Roca-Maza et al., PRC88, 024316(2013)

(αD) ~L

P ! " = α DE ! "

Electric Dipole Polarizability (αD)

Inversely energy weighted sum-rule of B(E1)

α D = !c 2π 2 σ abs

E1

ω 2 dω = 8π 9 dB E1

( )

ω

∫ ∫

α D

Restoring force ← symmetry energy

P ! " = αNE ! "

Requires the B(E1) distribution α: dipole polarizability of an atom

Sn Sp (PDR) GDR g.s.

• scillation of neutron

skin against core?

• scillation between

neutrons and protons

B(E1) 1-

core neutron skin

Low-Lying 
 Dipole Strength

Electric Dipole Response of Nuclei

Sn Sp (γ,xn)

neutron separation energy (p,p’) Low-lying E1
 (PDR)

IVGDR

(γ,γ’) NRF g.s. B(E1)

Electric Dipole Response of Nuclei

Coulomb excitation dominates

Real Photon Measurements, NRF or (γ,xn)

Probing the EM response of the target nucleus

Decay γ or n is detected.

Select q~0 (~0 deg.)

Missing Mass Spectroscopy with Virtual Photon Scattered p is detected.

EM Interaction is well known 
 (model independent)

A γ A * A γ (or xn) detector (or A-x)

A

p p

detector A *

virtual photon

Only the excitation part is probed.
 → total strengths independent of the decay channel

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

Experimental Method

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

RCNP Ring Cyclotron

High quality beams at 100-400 MeV/A

Grand Raiden Spectrometer

Large Angle Spectromete

Dispersion Matching Technique

ΔE=80-120 keV

ΔE=20-30 keV

(3He,t) at 420 MeV
 (p,p’) at 300 MeV

Spectrometers in the 0-deg. experiment setup

Intensity : 1-8 nA As a beam spot monitor in the vertical direction Dispersion Matching

Polarized Proton Beam at 295 MeV

Focal Plane Polarimeter AT et al., NIMA605, 326 (2009)

208Pb target: 5.2 mg/cm2

at RCNP, Osaka

Neglect of data for Θ>4: (p,p´) response too complex Included E1/M1/E2 or E1/M1/E3 (little difference)

B(E1): continuum and GDR region

Method 1: Multipole Decomposition

Grazing Angle = 3.0 deg

ΔS 1 ΔS for for 1 Transfer Spin Total

4 ) 2 ( 3

= =

! " # = + − ≡ Σ

LL SS

D D

spinflip / non-spinflip separation Polarization observables at 0° E1 / spin-M1 decomposition

• T. Suzuki, PTP 103 (2000) 859

E1

spin-M1

model-independent

B(E1): continuum and GDR region

Method 2: Decomposition by Spin Observables

Comparison between the two methods

Total ΔS = 1 ΔS = 0

Excellent agreement between (p,p’) and (γ,γ’) below ~Sn low-lying discrete states

• I. Poltoratska, PhD thesis

GDR region

Distribution of B(E1)

AT et al., PRL107, 062502(2011)

combined data The dipole polarizability of 208Pb has been precisely determined.

E1 Response of 208Pb and αD

Electric Dipole Response of 208Pb

Giant Dipole Resonance Low-lying Dipole Strength
 (Pygmy Dipole Resonance)

0"# 5"# 10"# 15"# 20"# 5" 10" 15" 20"

Excitation Energy (MeV)

Integrated Dipole Polarizability (fm3)

Electric Dipole Response of 208Pb

Giant Dipole Resonance Low-lying Dipole Strength
 (Pygmy Dipole Resonance)

0"# 5"# 10"# 15"# 20"# 5" 10" 15" 20"

Excitation Energy (MeV)

Integrated Dipole Polarizability (fm3)

0.0#$ 5.0#$ 10.0#$ 15.0#$ 20.0#$ 0.0## 20.0## 40.0## 60.0## 80.0## 100.0## 120.0## Dipole'Polarizability'alpha_D'(fm^3)

Excitation'Energy'(MeV)

alpha_D'in'208PbA

DP is saturating at around ~40 MeV.

Dipole Polarizability αD (fm3)

αD in 208Pb

0.0#$ 0.2#$ 0.4#$ 0.6#$ 0.8#$ 1.0#$ 1.2#$ 1.4#$ 1.6#$ 1.8#$ 0.0## 20.0## 40.0## 60.0## 80.0## 100.0## 120.0##

Energy'Weighted'Sum0Rule'(TRK'unit)7

Excitation'Energy'(MeV)

E10EWSR'in'208Pb7

Energy Weighted (TRK) Sum-Rule of 208Pb

Constraints

• X. Roca-Maza et al. PRC88, 024316 (2013)

Δrnp = 0 .165 ± (0 .009)expt 
 ± (0 .013)theor ± (0 .021)est fm for the estimated J=31 ± (2)est

Experimental Value = αD Constraint in the J-L plane

Symmetry Energy Parameters Neutron Skin Thickness

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
 χEFT: Chiral Effective Field Theory


M.B. Tsang et al., PRC86, 015803 (2012)

• I. Tews et al., PRL110, 032504 (2013)

QMC: S. Gandolfi, EPJA50, 10(2014).

QMC

Constraints on J and L

AT et al., EPJA50, 28 (2014).

C.J. Horowitz et al., JPG41, 093001 (2014)

Neutron Skin Thickness of 208Pb

• X. Roca-Maza et al., PRC88, 024316(2013)

ΔRnp = 0 .165 ± (0 .009)expt ± (0 .013)theor ± (0 .021)est fm for the estimated J=31 ± (2)est

Dipole Polarizability of 120Sn

(γ, n) (p, p’) (γ, xn) (γ, xn) αD (fm3)

1.12 ± 0.07

135 MeV

Total: αD = 8.93 ± 0.36 fm3

7.00 ± 0.29 0.82 ± 0.12

• T. Hashimoto et al., PRC92, 031305(R)(2015).

Constraints on J-L and n-skin thickness from DP Data

• T. Hashimoto et al., PRC92, 031305(R)(2015).

AT et al., PRL107, 062502 (2011). D.M. Rossi et al., PRL111, 242503 (2013). Data

• X. Roca-Maza et al., submitted to PRC

208Pb: 120Sn: 68Ni:

RCNP RCNP GSI

68Ni 120Sn

PDR in 120Sn

A.M. Krumbholtz et al., PLB744, 7(2015)

(γ,γ’): B. Özel-Tashenov, et al., 
 PRC90, 024304(2014)

The observed strength by (γ,γ’) is significantly smaller than the present (p,p’) data.

Work In Progress

• Measurements on 112Sn, 124Sn and on 92Zr, 94Zr, 96Zr, have been

done in May-June, 2015.


• Data analyses on 48Ca, 90Zr, 96Mo, and 154Sm

Zr isotopes: presentation by C. Iwamoto on Thursday

CAGRA+GR Campaign Exp. in 2016

• Study on PDR by (p, p’γ) and (α,α’γ)*1


isospin/surface property, transition density ang. dep.

• (6Li,6Li’γ) for IV spin-flip inelastic excitation*2

CAGRA(Clover Ge Array)

for γ-coincidence measurements

*1 A. Bracco, F. Crespi, V. Derya, M.N. Harakeh, T. Hashimoto, C. Iwamoto, A. Maj, P. von Neumann-Cosel, 


• N. Pietralla, D. Savran, A. Tamii, V. Werner, and A. Zilges et al.


*2 S. Noji, R.G.T. Zegers et al.,

Plan in the Next Year

• E. Ideguchi and M. Carpenter

CAGRA+GR Campaign Exp. in 2016

E441 5.0 days (6Li,6Li'γ) for IV spin-flip inelastic excitation E450 25.0 days (p,p'γ) and (α,α'γ) for PDR E454 6.0 days (p,p'γ) at 300 MeV and (α,α'γ) for PDR Total 36.0 days.

(p,p'γ) and (α,α’γ) for PDR in


64Ni, 90,94Zr, 120,124Sn, 206,208Pb

PDR like transition density GDR like transition densities

Estimated size of the statistical uncertainties

208Pb(p,p’) at Ep=80 MeV

dσ/dΩ (mb/sr)

θcm (deg)

n p Transition densities by QPM P.-G. Reinhard and W. Nazarewicz PRC87, 014324 (2013)

Plan in the Next Year

(γ, n) (p, p’) (γ, xn) (γ, xn)

Conclusion

• Electric dipole response of 208Pb and 120Sn: 


Measured precisely by proton inelastic scattering. IV properties of the effective interaction:

• Constraints on the symmetry energy
• Neutron skin thickness, pygmy dipole excitations

Isotope dependence on Sn and Zr have been measured.

• T. Hashimoto et al., to be published in PRC.