SFB 634 *Supported by the DFG within SFB 634 and 446 JAP 113/267/0-2 Complete dipole response in 208 Pb from high-resolution polarized proton scattering at 0°* Iryna Poltoratska Institut für Kernphysik, Technische Universität Darmstadt Motivation Experimental setup Results - Coulomb excitation - Multipole decomposition - Asymmetry Summary and outlook
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Complete dipole response in 208 Pb from high-resolution polarized proton scattering at 0°*
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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
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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
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Measured SpectrumBackground-Subtracted Spectrum
Pronounced fine structure of the GDR is recognized Strong Coulomb excitation of the GDR at 0°
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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
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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