Particles	Mass (MeV/c²)	Charge	Decays	Structure
Photon [2] [9]	0	0	Stable
Electron [2] [10]	0.511	−e	Stable
Positron [2] [10]	0.511	+e	Stable
μ ± leptons	106.6	±e	μ± → e± ν^e ν^μ [2] [17]
π ± mesons	139.6	±e	π± → μ± ν^μ [2] [17] [18]
π0 mesons	135.0	0	π0 → γ [2] [17]
Neutrinos [2] [13] [17]	Sum 0.00032	0	Stable
τ- leptons	1777	−e	τ- → (a) π- π0 ν^τ; (b) π- ν^τ; (c) π- 2π0ν^τ; et al. [3] [18]
Up quark	139.6	+e	π+ → μ+ ν^μ [2] [3] [17] [18]
Down quark	139.6	−e	π- → μ- ν^μ [2] [3] [17] [18]
Strange quark	95 ± 5	0	π0 → γ [2] [3] [17]