The η/s\eta /s of the LQCD-EoS complied hadron gas of different sizes approach common minimum near the crossover temperature

We study the temperature dependence of the ratio of the shear viscosity to entropy density for the LQCD-contrasted hadron resonance gas of different finite system-sizes, which may represent the final state hadronic matter, formed in systems of ultra-relativistic collisions. The transport coefficient reaches the lowest common value, for the systems of different sizes of thermalized hadron gas, near the critical temperature $T_{c}$ of the QCD crossover.Comment: 6 pages 6 figures. To appear in EPJ

Indication of transverse radial flow in high-multiplicity proton-proton collisions at the Large Hadron Collider

We analyze the measured spectra of $\pi^\pm$, $K^\pm$, $p$($\bar p$) in $pp$ collisions at $\sqrt {s}$ = 0.9, 2.76 and 7 TeV, in the light of blast-wave model to extract the transverse radial flow velocity and kinetic temperature at freeze-out for the system formed in $pp$ collisions. The dependency of the blast-wave parameters on average charged particle multiplicity of event sample or the `centrality' of collisions has been studied and compared with results of similar analysis in nucleus-nucleus ($AA$) and proton-nucleus ($pA$) collisions. We analyze the spectra of $K_{s}^0$, $\Lambda$($\bar \Lambda$) and $\Xi^-$ also to see the dependence of blast-wave description on the species of produced particles. Within the framework of the blast-wave model, the study reveals indication of collective behavior for high-multiplicity events in $pp$ collisions at LHC. Strong transverse radial flow in high multiplicity $pp$ collisions and its comparison with that in $pA$ and $AA$ collisions match with predictions from a very recent theoretical work [Shuryak and Zahed 2013 arXiv:1301.4470] that addresses the conditions for applicability of hydrodynamics in $pp$ and $pA$ collisions.Comment: 14 pages 8 figure