SFB 634

*Supported by the DFG within SFB 634 and 446 JAP 113/267/0-2

Complete dipole response in 208Pb from high-resolution polarized proton scattering at 0°*

Iryna PoltoratskaInstitut für Kernphysik,

Technische Universität Darmstadt

Motivation

Experimental setup

Results

- Coulomb excitation

- Multipole decomposition

- Asymmetry

Summary and outlook

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B(E1) Strength Distribution

04/21/23 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 3

ReminderThe Pygmy Dipole Resonance in 208Pb

Excellent agreement with QPM

N. Ryezayeva et al., PRL 89 (2002) 272502

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Structure of Low-energy E1 Modes

Oscillations of neutron skin Toroidal mode

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Elucidation of the Structure of the Low-Energy Modes

(e,e´) at backward angles - transverse response S-DALINAC, TU Darmstadt

(p,p´) at 0° - longitudinal response (Coulomb excitation) - sensitive to polarization observables RCNP, Osaka University

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Spin M1 Strength in 208Pb

Spin-flip M1 resonance is quenched - 208Pb as a test case

Problem studied in the 80’s but: - large experimental uncertainties

- improved model calculations

new experimental access by (p,p´) - intermediate energy region optimal for spin-isospin excitations

- at 0° selectivity on L=0 transitions

- isovector spin-flip M1 transitions enhanced

Overlap with PDR

04/21/23 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 7

Polarized Proton Scattering

intermediate energy

spinflip / non-spinflip separation

300 MeV optimal

angular distributions

high resolution measurements needed

- selectivity on L = 0 - Coulomb excitation

- Coulomb-nuclear interference

E1 / M1 separation

spin-isospin excitations

Multipole Decomposition

polarization observables at 0°

- measurements at 0°

- measurements at finite angles

LLNNSS DDD-1 for S = 1, M1 excitations

3 for S = 0, E1 excitations

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Cyclotron Facility at RCNP

AVF

HIPIS

Ring Cyclotron

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0o Setup at RCNP

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Focal Plane Detectors

Measured polarization observables:Ay - asymmetryDSS = DNN at 0° - sideway polarization transfer coefficientDLL at 0° - longitudinal polarization transfer coefficient

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Measured Spectrum

mildly under-focusing mode in non-dispersive direction flat distribution of the background on the Y focal plane determines shape and magnitude of the background

04/21/23 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 12

Measured SpectrumBackground-Subtracted Spectrum

Pronounced fine structure of the GDR is recognized Strong Coulomb excitation of the GDR at 0°

04/21/23 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 13

All dipole transitions known from (,´) are observed

Measured SpectrumLow-Energy Part

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Coulomb Excitation of E1 Transitions

*C.A. Bertulani et al., Comp. Phys. Comm. 152 (2003) 317

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Extracted Transition Strengths

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Spectra at Finite Angles

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Multipole Decomposition

Restrict angular distribution to 2.5° setting

L = 0

- theoretical d/d for IS and IV excitations are similar

L = 1

- angular distribution averaged over individual levels

L = 2

- substitute for all L > 1

J DWBAJ

data d

da

d

d )()(

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Experimental Asymmetry

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Experimental AsymmetryLow-Energy Part

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Summary and Outlook

First high-resolution zero degree polarized proton scattering

experiment on 208Pb performed Measured observables: d/d, Ay, DSS, DLL

Selective Coulomb excitation of 1- states at very forward angles

observed

Multipole decomposition analysis Analysis of the polarization observables Investigation of the dipole strength in 120Sn

04/21/23 | TU Darmstadt | Institut für Kernphysik | Iryna Poltoratska | 21

Pygmy Dipole Resonance in 120SnMeasured Spectra

B. Özel et al., PLB, submittedA. M. Heilmann, Poster, HK 67.6

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Pygmy Dipole Resonance in 120SnMeasured Spectra II

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Dep. of Phys., Osaka UniversityY. Fujita

Dep. of Phys., Kyoto UniversityH. Sakaguchi, J. Zenihiro

CNS, Univ. of TokyoY. Sasamoto

IFIC-CSIC, ValenciaB. Rubio

Univ. of WitwatersrandJ. Carter

GSI, DarmstadtB. Özel

RCNP, Osaka UniversityT. Adachi, H. Fujita, K. Hatanaka, M. Kato,

H. Matsubara, M. Okamura, Y. Sakemi,Y. Shimizu,Y. Tameshige, A. Tamii,

M. Yosoi

iThembaLABsR. Neveling, F.D. Smit

Texas A&M University, Commerece, USAC. Bertulani

IKP, TU DarmstadtO. Burda, A. M. Heilmann

Y. Kalmykov, P. von Neumann-Cosel, A. Richter, I. Poltoratska, V. Ponomarev

EPPS0 Collaborators

Thank you !!