Orateur
Description
The pygmy dipole resonance (PDR) is a low-energy dipole excitation commonly interpreted as the oscillation of a neutron skin against a core symmetric in number of protons and neutrons. Despite extensive experimental and theoretical efforts [1,2] the properties of the PDR remain an active field of investigation. Beyond its fundamental interest, the study of the PDR has been and still is of great interest since it allows to constrain the symmetry energy, an important ingredient of the equation of state of nuclear matter that describes the matter within neutron stars [3]. It may also have important implications for the r-process, through its potential impact on neutron-capture rates [4].
However, a fully consistent picture of the PDR has yet to emerge. In this context, we have started in 2022 an experimental program exploiting a novel probe: the neutron inelastic scattering reaction (n,n’). As a first step, we studied the PDR in 140Ce using the (n,n’) reaction. This experiment was made possible thanks to the high-intensity proton beam of the new accelerator SPIRAL2 at GANIL and the NFS (Neutron For Science) facility [5]. The experimental setup consisting of the new generation multi-detectors PARIS [6], for the detection of gammas coming from the de-excitation of the PDR, and MONSTER [7], for the detection of scattered neutrons, was used. The experimental results obtained for 140Ce will be presented and discussed [8,9,10]. Finally the perspectives of this experimental program will be outlined, focusing in particular on our recently accepted experiment dedicated to the study of the PDR in 88Sr.
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[2] A. Bracco, E.G. Lanza, A. Tamii, Prog. Part. Nucl. Phys. 106, 360-433 (2019)
[3] A. Carbone et al., Phys. Rev. C 81, 041301(R) (2010)
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[5] X. Ledoux et al., Eur. Phys. J. A. 57, 257 (2021)
[6] F. Camera, A. Maj. PARIS White Book (2021)
[7] T. Martinez et al., Nucl. Data Sheets 120, 78-80 (2014)
[8] M. Vandebrouck et al., Il Nuovo Cimento 47, 19 (2024)
[9] P. Miriot-Jaubert et al., Acta Phys. Pol. B Proc. Suppl. 18, 2-A35 (2025)
[10] P. Miriot-Jaubert et al., Eur. Phys. J. A. 62, 175 (2026)