Shear viscosity of a pion gas resulting from ρππ and σππ interactions

Abstract

We have evaluated the shear viscosity of pion gas with vanishing chemical potential taking into account its scattering with the low mass resonances σ and ρ during propagation in the medium. The thermal width (or collisional rate) of pions is calculated from πσ and πρ loop diagrams using effective interactions in the real-time formulation of finite temperature field theory. A very small value of shear viscosity by entropy density ratio (η/s), close to the quantum bound, is obtained which approximately matches the range of values of η/s used by Niemi et al. [H. Niemi, G. S. Denicol, P. Huovinen, E. Molnár, and D. H. Rischke, Phys. Rev. Lett. 106, 212302 (2011)PRLTAO0031-900710.1103/PhysRevLett.106.212302; Phys. Rev. C 86, 014909 (2012)PRVCAN0556-281310.1103/PhysRevC.86.014909] to fit the elliptic flow data from the Relativistic Heavy Ion Collider. © 2014 American Physical Society.