muoneutriino

The muon neutrino (νμ) is an elementary particle of the lepton family. It is the neutrino associated with the muon, one of the three charged leptons, and it belongs to the second generation of leptons.

As a neutral, spin-1/2 fermion, the muon neutrino carries no electric charge and participates in weak interactions. It has lepton number Lμ = +1, and it couples to the W and Z bosons, but not to photons. It interacts with matter primarily through the weak force, making it difficult to detect compared with particles that participate in electromagnetism or the strong interaction.

The muon neutrino is extremely light, with no precise single mass value assigned because flavor states are superpositions of mass eigenstates. In the standard three-neutrino framework, flavor eigenstates are related to mass eigenstates by the PMNS mixing matrix. Neutrino oscillations—transitions between νμ, νe, and ντ—demonstrate nonzero mass differences among the eigenstates and imply sub-eV scale masses.

Production and detection: νμ is produced in processes such as the decays of pions and kaons (for example, π+ → μ+ νμ) and in muon decay (μ− → e− ν̄e νμ). It is detected via charged-current interactions that yield a muon in the final state, or via neutral-current interactions that leave the neutrino intact.

History: The muon neutrino was identified in 1962 by experiments at Fermilab (and Brookhaven) led by Leon Lederman, Melvin Schwartz, and Jack Steinberger, establishing a distinct neutrino flavor associated with muons.

In research, νμ studies test the structure of the weak interaction, probe neutrino oscillations, and contribute to our understanding of astrophysical and cosmological neutrinos.