nonhadronic

Nonhadronic is a term used in physics to describe processes, interactions, or states that do not involve hadrons in the initial or final state, or that proceed without the strong interaction playing a significant role. Hadrons are particles such as protons, neutrons, and mesons, which are bound by the strong force. By contrast, nonhadronic processes are typically governed by electromagnetic or weak interactions, or involve particles that are not hadrons, such as leptons, photons, and gauge bosons.

In particle physics, nonhadronic processes include electron-positron annihilation into lepton pairs (for example, muon or electron-positron final states), neutrino or antineutrino scattering mediated by the weak force, and photon- or electroweak-boson production without resulting in hadronic final states. Nonhadronic decays of hadrons can also occur when the decay products are leptons or photons rather than other hadrons.

Experimentally, distinguishing hadronic from nonhadronic events helps in event selection and analysis, since hadronic channels often involve strong-interaction effects and higher multiplicities, while nonhadronic channels may provide cleaner signatures but may have smaller cross sections. In broader contexts, the term may refer to matter or processes that do not involve hadrons, such as leptonic matter or photon-dominated phenomena, though its use is most common in particle- and nuclear-physics discussions.

See also: hadron, lepton, electromagnetic interaction, weak interaction, particle decay.