  We study the system-size dependence of Knudsen number, a measure of degree of
thermalization, for hadron resonance gas that follows the Lattice-QCD equation
of state at zero chemical potential. A comparison between Knudsen numbers for
the AuAu collisions at RHIC and the hadron gas of size similar to the size of
high-multiplicity pp events at LHC, reassures the applicability of
hydrodynamics in interpreting the features of particle production in
high-multiplicity pp events.

High Energy Physics - Phenomenology;High Energy Physics - Experiment;Nuclear Theory