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Shear viscosity of a hadron gas and influence of resonance lifetimes on relaxation time
- Source :
- Phys. Rev. C 97, 055204 (2018)
- Publication Year :
- 2017
-
Abstract
- We address a discrepancy between different computations of $\eta/s$ (shear viscosity over entropy density) of hadronic matter. Substantial deviations of this coefficient are found between transport approaches mainly based on resonance propagation with finite lifetime and other (semi-analytical) approaches with energy-dependent cross-sections, where interactions do not introduce a timescale. We provide an independent extraction of this coefficient by using the newly-developed SMASH (Simulating Many Accelerated Strongly interacting Hadrons) transport code, which is an example of a mainly resonance-based approach. We compare the results from SMASH with numerical solutions of the Boltzmann equation for simple systems using the Chapman-Enskog expansion, as well as previous results in the literature. Our conclusion is that the hadron interaction via resonance formation/decay strongly affects the transport properties of the system, resulting in significant differences in $\eta/s$ with respect to other approaches where binary collisions dominate. We argue that the relaxation time of the system ---which characterizes the shear viscosity--- is determined by the interplay between the mean-free time and the lifetime of resonances. We show how an artificial shortening of the resonance lifetimes, or the addition of a background elastic cross section nicely interpolate between the two discrepant results.<br />Comment: 15 pages, 16 figures
- Subjects :
- Nuclear Theory
High Energy Physics - Phenomenology
Subjects
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. C 97, 055204 (2018)
- Publication Type :
- Report
- Accession number :
- edsarx.1709.03826
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevC.97.055204