Lightest up-type quark; along with the down quark, a constituent of nucleons (proton = uud, neutron = udd). Spin-½, colour-charged fermion; confined inside hadrons by QCD.
Lightest up-type quark; along with the down quark, a constituent of nucleons (proton = uud, neutron = udd). Spin-½, colour-charged fermion; confined inside hadrons by QCD.