Evidence for a quadruple kinetic freeze-out scenario in small and large systems

In this study, we propose a novel quadruple kinetic freeze-out scenario observed in both high-energy heavy-ion and proton–proton collisions, wherein different categories of produced particles decouple from the system at distinct stages. Specifically, non-strange hadrons, singly-strange hadrons, multi-strange hadrons, and light nuclei such as deuterons ( d ), tritons ( t ), and helions ( ³He 3 H e ) each exhibit unique freeze-out behavior. The analysis is performed using the Boltzmann-Gibbs Blast-Wave (BGBW) model applied to transverse momentum spectra across multiple centrality classes. Within each species group, the kinetic freeze-out temperature ( T₀ T 0 ) and average transverse flow velocity ( β T ⟨ β T ⟩ ) are reported to be constant, while the transverse flow profile varies. The extracted parameters show a clear centrality dependence: T₀ T 0 decreases and β T ⟨ β T ⟩ increases with increasing collision centrality. Moreover, the results reveal a systematic increase in kinetic freeze-out temperature and a simultaneous decrease in transverse flow velocity from non-strange to strange, multi-strange, and composite particle species, highlighting the compositional dependence of freeze-out dynamics. These findings provide strong evidence for an Extended Freeze-Out Hierarchy, offering new insights into the sequential decoupling dynamics and collective evolution of hadronic and composite matter in high-energy collisions.