Programme

I.6 -- Invited, IWTCP-2

Date: Tuesday, 29-07-2014

Time: 16h35 - 17h10

Recent achievements in the study of thermal pairing and giant resonances in highly excited nuclei

Nguyen Dinh Dang

1) Theoretical Nuclear Physics Laboratory, Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako city, 351-0198 Saitama, Japan; 2) Institute for Nuclear Science and Technique, Hanoi, Vietnam

Recent experimental and theoretical results are presented, which show the effect of thermal pairing in highly excited nuclei. It is demonstrated that thermal pairing included in the phonon damping model (PDM) [1] is responsible for the nearly constant width of the giant dipole resonance (GDR) at low temperature T < 1 MeV [2]. It is also shown that the enhancement observed in the recent experimentally extracted nuclear level densities in 104Pd at low excitation energy and various angular momenta is the first experimental evidence of the pairing reentrance in a finite (hot rotating) nucleus [3]. In the study of GDR in highly excited nuclei, the phonon damping model (PDM) has been extended to include finite angular momenta. The results of calculations within the PDM are found in excellent agreement with the latest experimental data of GDR in the compound nucleus 88Mo [4]. Finally, an exact expression has been derived to calculate the shear viscosity $\eta$ as a function of T in finite nuclei directly from the GDR width and energy at zero and finite T. Based on this result, the values $\eta$/s of specific shear viscosity in several medium and heavy nuclei were calculated and found to decrease with increasing T to reach $(1.3 - 4) \times \hbar/(4\pi k_B)$ ($k_B$ is the Boltzmann constant) at T = 5 MeV, that is almost the same value obtained for quark-gluon-plasma at T > 170 MeV [5]. References: [1] N. Dinh Dang and A. Arima, Phys. Rev. Lett. 80 (1998) 4145, Nucl. Phys. A 636 (1998) 427. [2] N. Dinh Dang and N. Quang Hung, Phys. Rev. C 86 (2012) 044333; B. Dey et al., Phys. Lett. B 731 (2014) 92. [3] N. Dinh Dang, N. Quang Hung, B.K. Agrawal, V.M. Datar, A. Mitra, and D.R. Chakrabarty, in preparation. [4] N. Dinh Dang, M. Ciemala, M. Kmiecik, and A. Maj, Phys. Rev. C 87 (2013) 054313. [5] N. Dinh Dang, Phys. Rev. C 84 (2011) 034309.

Presenter: Nguyen Dinh Dang