1-5 July 2019
Africa/Johannesburg timezone
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Nature of the Pygmy Dipole Resonance: A multi-messenger approach

Not scheduled
15m
Invited Talk

Speaker

Dr Deniz Savran (GSI)

Description

Beside the Giant Dipole Resonance (GDR), many nuclei show the feature of additional low-lying electric dipole (E1) strength below and around the particle separation energies, which is usually denoted as Pygmy Dipole Resonance (PDR) [1]. The existence of the PDR in nearly every studied nucleus and the smooth variation of its properties lead to the assumption that the PDR is a newly discovered collective mode. While some of the gross characteristics are reproduced by different theoretical model descriptions, its detailed structure and the degree of collectivity are a matter of ongoing discussions.
Most of the so far available experimental data has been obtained in photon induced reactions or coulomb excitation [1]. Photon-induced reactions alone are, however, not sensitive to the structure of the E1 excitations. We have therefore started a campaign to provide additional experimental data using complementary probes or observables. For the semi-magic nucleus 140Ce we have combined the results from experiments using the (g,g’), (a,ag’) at E = 134 MeV and (p,pg’) at E = 80 MeV reactions, the letter one is the first time this reaction has been used at this energy to investigate the PDR [2]. In addition, recently the decay properties of the PDR in 140Ce have been determined for the first time with high precision using the novel gamma3 setup at HIgS [3]. For each experimental reaction and observable corresponding calculations have been performed within the Quasi-particle Phonon Model (QPM), i.e. all observables are compared simultaneously based on the same wave functions. This multi-messenger investigation provides a comprehensive test of the quality of the theoretical model [2]. The results for 140Ce and an outlook to further investigations will be presented.

  1. D. Savran, T. Aumann, A. Zilges, Prog. Part. Nucl. Phys., 70, 210 (2013).
  2. D. Savran et al., Phys. Lett B 786 (2018) 16
  3. B. Löher et al., Phys. Lett. B 756 (2016) 72

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