Classify particles and calculate charges of baryons, mesons and antiparticles.
Method and worked examples
The Standard Model describes quarks, leptons and interaction-carrying bosons. Electrons, muons, taus and their neutrinos are leptons and do not participate in the strong interaction. Quarks do participate in it. Up, charm and top quarks have charge +⅔e; down, strange and bottom have −⅓e. Antiquarks have opposite charge. Ordinary baryons contain three quarks; ordinary mesons contain a quark and an antiquark.
Photons mediate electromagnetic interactions, gluons the strong interaction, and W and Z bosons the weak interaction. The Higgs is a scalar boson associated with the Higgs field. Gravity lies outside the established Standard Model; the proposed graviton is unobserved. Antiparticles have the same rest mass and opposite signed charges where nonzero. Quarks are not observed in isolation. Add constituent charges algebraically; neutral neutrinos remain leptons.
Example 1
Find the charge of a proton with quark content uud.