EURORIB'12

Dynamical Dipole and EOS in N/Z asymmetric fusion reactions with stable and unstable beams

25 May 2012, 09:50

20m

Centro Congressi delle Venezie, Hotel Alexander Palace - Abano Terme (Padova) - Italy

Oral Dynamics and Thermodynamics of exotic nuclear systems Dynamics and Thermodynamics of exotic Nuclear Systems

Speaker

Ms Agnese Giaz (MI)

Description

The study of the collective properties of a nuclear system is a powerful tool to understand the structure of the nucleus. A successful technique which has been used in this field is the measurement of the decay of the Giant Dipole Resonance (GDR) which can be used as probe for hot nuclei and, in addition, constitutes a clock for the thermalization process. Using fusion-evaporation reactions, it has been recently possible to study the yield of the high-energy gamma-ray emission from Dynamical Dipole (DD) mechanism which takes place during fusion processes when there is a N/Z asymmetry between projectile and target. A good understanding of the DD is important because this emission depends on several key parameters like the Nuclear Equation of State (EOS) and the in medium N-N cross sections. This is more relevant using exotic systems which have a large N/Z asymmetry. In addition, the DD yield is expected to depend on the energy of the projectile and on the size of the D(0) parameter defined as weighted difference between the projectile and target N/Z asymmetry [5]. By general arguments it is expected an increase of the DD yield with beam energy (the dynamics in the neck region between projectile and target become faster) followed by a decrease of the yield (because of the damping related to fast processes like pre-equilibrium neutron emission). Similarly, it is expected an increase for the DD yield with D(0). In the framework of a molecular dynamics theoretical model (BNV) is it possible to test the sensitivity of the measurable DD total yield for different nuclear EOS [1]. It has been observed and it will be shown that, using stable projectiles and targets in particular experimental conditions, different EOS produce different DD yield and that this difference increase significantly using to exotic beams like 132Sn. It was found that in reactions with a small impact parameters, the DD centroid energy and yield strongly depends on the used EOS. This effect greatly increases with the N/Z asymmetry and predictions will be given for the extreme case 132Sn+58Ni for different beam energies. From the esperimental side, to validate the theoretical predictions of the BNV model, a campaign focused on the measurement of the total DD yield in the mass region A ≈ 132 has been performed at the Laboratori Nazionali di Legnaro using GARFILED-HECTOR arrays (respectively for light charged particles and gamma-rays detection) coupled to phoswich detectors (for the measurement of fusion residues). In this campaign the DD emission in the fusion reaction 16O (Elab=192 MeV) + 116Sn has been measured in function of beam energy (in particular at 8.1 A MeV/A, at 12 A MeV and at 15.6 A MeV) [2]. The measured DD yields and angular distributions will be compared with the theoretical results and with the already existing experimental data in the same mass region [3], [4]. [1] V. Baran et al. Phys. Rev. Lett. 87 (2001) 182501 [2] A. Corsi et al. Phys. Lett. B 679 (2009) 197 [3] D. Pierroutsakou et al. Phys. Rev. C 80 (2009) 024612 [4] B. Martin et al. Phys. Lett. B 664 (2009) 47 [5] C. Simenel et al. Phys. Rev. Lett. 86 (2001) 2971

Presentation materials

Slides

A_Giaz.pdf