Study of the hadron gas phase using short-lived resonances with ALICE

Abstract

Short-lived hadronic resonances are unique tools for studying the hadron-gas phase that is created in the late stages of relativistic heavy-ion collisions. Measurements of the yield ratios between resonances and the corresponding stable particles are sensitive to the competing rescattering and regeneration effects. These measurements in small collision systems, such as pp and p-Pb, are a powerful method to reveal a possible short-lived hadronic phase. In addition, resonance production in small systems is interesting to study the onset of strangeness enhancement, collective effects,and the hadron production mechanism. On this front, the $\phi$ meson is particularly relevant since its yield is sensitive to different production models: no effect is expected by strange number canonical suppression but its production is expected to be enhanced in the rope-hadronization scenario. In this presentation, recent measurements of hadronic resonances in different collision systems,going from pp to Pb-Pb collisions, are presented. These include transverse momentum spectra,yields, and yield ratios as a function of multiplicity. The presented results are discussed in the context of state-of-the-art phenomenological models of hadron production. The resonance yields measured in Pb-Pb collisions are used as an experimental input in a partial chemical equilibrium-based thermal model to constrain the kinetic freeze-out temperature. This is a novel procedure that is independent of assumptions on the flow velocity profile and the freeze-out hypersurface.