Finite size effect on thermodynamics of hadron gas in high-multiplicity events of proton-proton collisions at the LHC

Multiple Reflection Expansion (MRE) formalism has been applied to hadron resonance gas (HRG) model to study the finite-size effect on thermodynamics of small systems of hadron gas at the chemical freeze-out temperature in high-multiplicity events of proton-proton (pp) colisions at the LHC. Comparison with larger systems of heavy-ion (AA) collisions helps in undersanding the usefulness of the effect on small systems. Thermodynamic properties of these systems at the chemical freeze-out, with and without system-size effect, are contrasted with those for infinite hadronic phase of strongly interacting matter at ideal thermodynamic limit, as provided by LQCD calculations. On introduction of finite size effect, the small hadronic systems produced in high-multiplicity pp events, unlike those in AA collisions, remain away from ideal thermodynamic limit. Knudsen number estimations validate the findings.