Hadrondominated

Hadrondominated is a term used in theoretical physics to describe a regime in which hadronic degrees of freedom provide the primary description of a system, with quark and gluon (partonic) contributions playing a subleading role. The concept is often invoked when confinement remains effective and the relevant excitations are hadrons, such as in low- to moderate-temperature or low-density settings.

Formal criteria for hadron dominance are model-dependent but generally involve comparing the contributions of hadronic states to observables (such as thermodynamic quantities or reaction rates) against those from partonic degrees of freedom. If the hadronic sector yields the majority of the observable strength across the regime of interest, the system is said to be hadron-dominated.

In practice, the term appears in discussions of hadron resonance gas models, chiral effective theories, and certain lattice QCD analyses near the confinement-deconfinement crossover. It is also used to describe the late-stage evolution of matter created in heavy-ion collisions, where hadronic interactions govern dynamics after the system cools below the deconfinement temperature.

Hadrondominated contrasts with parton-dominated or quark-gluon plasma regimes, where quarks and gluons provide the leading degrees of freedom. The boundary between hadron-dominated and parton-dominated descriptions is not sharp; it depends on the observable, energy scale, and chosen theoretical framework. Limitations include potential ambiguity near crossover regions and the context dependence of the dominance criterion.

See also: Hadron resonance gas model, hadronization, quark-gluon plasma, confinement, effective field theory.