Short-Lived Resonances as Probes of the Medium Produced in Heavy-Ion Collisions

Hadronic resonances play an important role in the study of the physics of heavy-ion collisions. In these proceedings, we discuss how the resonances can probe the reaction dynamics, the strangeness production and the properties of the hadronic phase in heavy-ion collisions at center-of-mass energies of sNN = 4–11 GeV. The resonance properties predicted by the general-purpose event generators are found to be very sensitive to the properties and space-time evolution of the medium produced in heavy-ion collisions.

Energy and multiplicity dependence of hadronic resonance production with ALICE at the LHC

The study of hadronic resonances plays an important role both in pp and in heavy-ion collisions. Since the lifetimes of short-lived resonances are comparable with the lifetime of the fireball formed in heavy-ion collisions, regeneration and re-scattering effects can modify the measured yields, especially at low transverse momentum. Measurements in pp collisions at different energies constitute a baseline for studies in heavy-ion collisions and provide constraints for tuning QCD-inspired event generators. Furthermore, high multiplicity pp collisions, where the density and the volume of the system are expected to be larger compared to minimum bias pp collisions, can help in the search for the onset of collective phenomena. Here we present recent results on short-lived hadronic resonances obtained by the ALICE experiment at LHC energies in different collision systems (pp, p–Pb and Pb–Pb) including new results obtained in Xe–Xe collisions. The ALICE results on transverse momentum spectra, yields and their ratios to long-lived particles will be discussed.

Hadronic footprint of GeV-mass dark matter

GeV-scale dark matter is an increasingly attractive target for direct detection, indirect detection, and collider searches. Its annihilation into hadronic final states produces a challenging zoo of light hadronic resonances. We update Herwig7 to study the photon and positron spectra from annihilation through a vector mediator. It covers dark matter masses between 250 MeV and 5 GeV and includes an error estimate.

High energy hadron production as self-organized criticality

In high energy nuclear collisions, production rates of light nuclei as well as those of hadrons and hadronic resonances agree with the predictions of an ideal gas at a temperature [Formula: see text][Formula: see text]MeV. In an equilibrium hadronic medium of this temperature, light nuclei cannot survive. We propose that the observed behavior is due to an evolution in global non-equilibrium, leading to self-organized criticality. At the confinement point, the initial quark-gluon medium becomes quenched by the vacuum, breaking up into all allowed free hadronic and nuclear mass states without formation of any subsequent thermal hadronic medium.