Coalescence Models for Hadron Formation from Quark-Gluon Plasma

Abstract

We review hadron formation from a deconfined quark gluon plasma (QGP) via coalescence or recombination of quarks and gluons. We discuss the abundant experimental evidence for coalescence from the Relativistic Heavy Ion Collider (RHIC) and compare the various coalescence models advocated in the literature. We comment on the underlying assumptions and remaining challenges as well as the merits of the models. We conclude with a discussion of some recent developments in the field.

Soft Particle Production, Flow and Correlations in Heavy Ion Collisions at the LHC

“…In these models, hadrons are formed assuming that the partons from the QGP recombine with each other or with partons from hard processes to form bound states. [32]. This mechanism is expected to dominate at intermediate p T , and would lead to an enhanced production of baryons due to the steeply falling parton spectrum.…”

Strange hadrons and resonances at LHC energies with the ALICE detector

“…The peak is shifted towards high transverse momentum going from peripheral to central collisions. One possible explanation of the so-called "baryon anomaly", alredy observed at RHIC energies, is the recombination of quarks (coalescence) as an additional hadronization mechanism [11] in presence of a deconfined medium. In general, the interplay of effects as flow, recombination and fragmentation has to be taken into account when modeling the intermediate p T region in ultrarelativistic heavy-ion collisions.…”

Strangeness production as a function of charged particle multiplicity in proton–proton collisions

“…Heavy-ion experiments at RHIC and LHC have been exploited to investigate strangeness production at higher collision energies, revealing several features, such as the baryon/meson anomaly and lower enhancement at higher energy, which have been triggering further theoretical investigations (for a complete review see [3]). Quark coalescence has been used to explain the intermediate-p T baryon/meson enhancement [4], while statistical hadronization models succeeded in describing hadron yields [5] using a grand-canonical approach. In the statistical model, strangeness production in small systems is affected by "canonical suppression", resulting in decreased production rates compared to those measured in larger systems.…”