GeVscale

GeVscale refers to energy regimes characteristic of roughly 1 GeV to a few tens of GeV, where hadrons are the primary degrees of freedom and quantum chromodynamics (QCD) is strongly coupled. The GeVscale is contrasted with higher-energy regimes where perturbative QCD is applicable and with lower-energy regimes where certain effective theories become dominant.

GeVscale phenomena include the light hadron spectrum, resonance structures, and hadronic decays, as well as the production of heavier hadrons near their thresholds. Experimental programs operate in this range through electron-positron colliders at a few GeV, fixed-target experiments, and studies of kaons, pions, and nucleon form factors.

Theoretical tools commonly used at the GeVscale include lattice QCD, which computes hadron masses, decay constants and matrix elements from first principles; chiral perturbation theory for interactions of pions, kaons and nucleons at energies around or below 1 GeV; and phenomenological models or QCD sum rules. Observables typical of GeVscale physics include hadron masses and widths, decay constants such as f_pi, form factors, and low-energy scattering amplitudes.

GeVscale physics provides a bridge between nonperturbative dynamics at low energies and the perturbative regime at higher energies, and it is essential for precision tests of the Standard Model, including hadronic contributions to the muon anomalous magnetic moment and other electroweak observables that involve hadronic corrections.