Thermal pairing and giant dipole resonance in highly excited nuclei

Abstract

Recent results are reported showing the effects of thermal pairing in highly excited nuclei. It is demonstrated that thermal pairing included in the phonon damping model (PDM) is responsible for the nearly constant width of the giant dipole resonance (GDR) at low temperature $T<$ 1 MeV. It is also shown that the enhancement observed in the recent experimentally extracted nuclear level densities in ${}^{104}$Pd at low excitation energy and various angular momenta is the first experimental evidence of the pairing reentrance in finite (hot rotating) nuclei. In the study of GDR in highly excited nuclei, the PDM has been extended to include finite angular momentum. The results of calculations within the PDM are found in excellent agreement with the latest experimental data of GDR in the compound nucleus ${}^{88}$Mo. Finally, an exact expression is 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 $(1.3-4)\times \hslash /(4\pi k_B)$ at $T=$ 5 MeV, that is almost the same value obtained for quark-gluon-plasma at $T>$ 170 MeV.

arXiv comment6 pages, 4 figures, invited lecture at the 11th Spring Seminar on Nuclear Physics, Ischia May 12 - 16, 2014

References in corpus (11)

• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Compilation of Giant Electric Dipole Resonances Built on Excited States
• Pairing effect on the giant dipole resonance width at low temperature
• Probing the critical behavior in the evolution of GDR width at very low temperatures in A~100 mass region
• The shear viscosity to entropy density ratio in finite nuclei
• Shear-Viscosity to Entropy-Density Ratio from Giant Dipole Resonances in Hot Nuclei
• Pairing reentrance in hot rotating nuclei
• Pairing in hot rotating nuclei
• Giant dipole resonance in ${}^{201}$Tl at low temperature
• Damping of giant dipole resonance in hot rotating nuclei
• Giant dipole resonance in ${}^{88}$Mo from phonon damping model's strength functions averaged over temperature and angular momentum distributions