In high energy physics, a particle called lambda has zero charge and may be thought of as a neutron with a strange quark replacing a down quark. One way this particle decays is by conversion into proton and emission of a muon and a muon antineutrino via the weak interaction, despite no leptons being present initially.
How leptons can arise from lambda decay, use your understanding of the quark model of hadrons and the boson model of the weak interaction.