Experimental Determination of $\eta$/$s$ for Finite Nuclear Matter

Abstract

We present, for the first time, simultaneous determination of shear viscosity ($\eta$) and entropy density ($s$) and thus, $\eta /s$ for equilibrated nuclear systems from $A$ $\sim$ 30 to $A$ $\sim$ 208 at different temperatures. At finite temperature, $\eta$ is estimated by utilizing the $\gamma$ decay of the isovector giant dipole resonance populated via fusion evaporation reaction, while $s$ is evaluated from the nuclear level density parameter ($a$) and nuclear temperature ($T$), determined precisely by the simultaneous measurements of the evaporated neutron energy spectra and the compound nuclear angular momenta. The transport parameter $\eta$ and the thermodynamic parameter $s$ both increase with temperature resulting in a mild decrease of $\eta$/$s$ with temperature. The extracted $\eta$/$s$ is also found to be independent of the neutron-proton asymmetry at a given temperature. Interestingly, the measured $\eta$/$s$ values are comparable to that of the high-temperature quark-gluon plasma, pointing towards the fact that strong fluidity may be the universal feature of the strong interaction of many-body quantum systems.

arXiv commentAccepted for publication in Physical Review Letters, 6 pages, 4 figures

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• Phenomenological bound on the viscosity of the hadron resonance gas
• Mean free path and shear viscosity in central ${}^{129}$Xe+${}^{119}$Sn collisions below 100 MeV/nucleon
• Temperature dependence of nuclear fission time in heavy-ion fusion-fission reactions
• Green-Kubo formula for Boltzmann and Fermi-Dirac statistics
• Viscosity calculations from Hadron Resonance Gas model: Finite size effect
• Temperature and density effects on the two-nucleon momentum correlation function from excited single nuclei
• Estimation of transport coefficients of dense hadronic and quark matter
• First-Order Viscous Relativistic Hydrodynamics on the Two-Sphere