Utilizing hadronic resonances to probe the onset of QGP effects

The scientific programs of both RHIC and the LHC have shown substantial experimental evidence of a strongly interacting medium in heavy-ion (AA) collisions, commonly referred to as the quark-gluon plasma (QGP). However, measurements in high-multiplicity proton-proton (pp) and proton-lead (p-Pb) collisions have revealed that phenomena traditionally associated with the QGP can be observed in smaller collision systems. The concept of the formation of a strongly interacting medium in these smaller collision systems challenges current theoretical frameworks, thereby also complicating the interpretation of these observations in heavy-ion collisions.

Measurements of short-lived, hadronic resonances can give insight into the relative prevalence of either more traditional QCD-inspired or QGP/AA-like paradigms in the continuous crossover from small-to-large collision systems. For example, the phi meson is a strongly decaying s-sbar resonance, which puts constraints on hadronization mechanisms during the early stages of the collision. In string-like QCD-inspired models, quantum numbers are conserved microscopically. In this context, while the phi meson itself is strangeness neutral, it has to produce a significant amount of associated strangeness in near-phase space to conserve strangeness. This is in stark contrast to QGP-like models, where the phi meson is produced already strangeness neutrally through statistical/thermal means. Therefore, the effective strangeness of the phi meson is model-dependent, even though the meson itself is always strangeness-neutral.

Furthermore, contrasting the lifetime and production of various resonances with different lifetimes an excellent probe of the hadronic phase produced in QGP(-like) paradigms, and potential rescattering effects.

This talk will showcase a wide range of multi-differential measurements on hadronic resonance production, both from experiments in the LHC and RHIC and over small-and-large collision systems, to understand where and how QCD-like or QGP-like paradigms are prominent. The measurements will be compared to several general-purpose Monte Carlo generators, encompassing a wide range of both e+e--like and AA-like phenomenologies.