Pions

A pion (π meson) is a particle that can be positively charged, negatively charged or neutral.

π⁺ π^- π⁰

The rest mass of a muon μ is less than the rest mass of a pion π which is less than the rest mass of a proton.Pions are produced through the strong interaction. The decay of pions is through the weak interaction.A charged pion can decay into a muon and an antineutrino or a charged pion can decay into an antimuon and a neutrino.

π^-   →   μ^- + anti-ν

π⁺   →   μ⁺ + ν

A π⁰ meson decays into high energy photons.