hadronspektrum

In particle physics, hadrons are strongly interacting composite particles made of quarks bound by gluons. The hadron spectrum is the set of all possible hadronic states, characterized by mass, spin, parity, flavor, and decay properties. The spectrum includes mesons (quark-antiquark) and baryons (three quarks), and potentially exotic configurations.

The quark model organizes hadrons into multiplets, aided by quantum numbers such as isospin, strangeness, charm, and bottom. Quantum chromodynamics provides the underlying theory, but practical predictions for the spectrum use approaches such as potential models for heavy quarkonia and lattice QCD for all quarks. Regge trajectories relate the spin and mass of families of hadrons.

Experimentally, states appear as resonances in scattering and decay channels. Widths reflect lifetimes. The Particle Data Group maintains a catalog of established states. Light mesons and baryons form densely populated spectra, while heavy quarkonia (charmonium, bottomonium) exhibit cleaner, more regular level structures.

The spectrum includes exotic hadrons, such as tetraquarks, pentaquarks, hybrids, and glueballs, which challenge the simple quark model. Some candidates have been reported in recent experiments (LHCb, Belle, BESIII), but interpretations remain debated. Lattice QCD continues to refine predictions for both conventional and exotic states.

Studying the hadron spectrum tests quantum chromodynamics, informs confinement dynamics, and helps determine quark masses and interactions. Ongoing experiments and computational advances aim to complete the picture of how quarks form the visible matter of the strong interaction.