leptonic

Leptonic is an adjective relating to leptons, a family of elementary particles in the Standard Model. Leptons include three charged particles—the electron, muon, and tau—and their corresponding neutrinos (electron neutrino, muon neutrino, and tau neutrino). They are fermions with half-integer spin and do not participate in strong interactions. Charged leptons carry electric charge and interact electromagnetically and through the weak force; neutrinos interact only via the weak interaction (and gravity).

Leptons come in three generations. Neutrinos have very small masses and can change flavor as they propagate, a phenomenon known as neutrino oscillation. This behavior indicates physics beyond a strictly massless neutrino picture. In general, leptons are produced and interact through electromagnetic and weak processes, while neutrinos interact only weakly, making them challenging to detect directly.

Leptonic processes describe interactions or decays that involve leptons. Classic examples include muon decay (mu -> e + nu_e + anti-nu_mu) and W boson decays to a charged lepton and its neutrino. In high-energy experiments, final states containing leptons are referred to as leptonic channels or leptonic events, because leptons offer relatively clean experimental signatures compared with hadronic final states. Leptonic decays also occur in mesons, such as B mesons decaying to a lepton and a neutrino (for example, B -> tau nu or D_s -> mu nu), which provide important tests of the Standard Model and its extensions.