The
up quark or
u quark (symbol:
u) is the lightest of all
quarks, a type of
elementary particle, and a major constituent of
matter. It, along with the
down quark, forms the
neutrons (one up quark, two down quarks) and
protons (two up quarks, one down quark) of
atomic nuclei. It is part of the
first generation of matter, has an
electric charge of +
e and a bare mass of 1.8–. Like all
quarks, the up quark is an
elementary fermion with
spin-, and experiences all four
fundamental interactions:
gravitation,
electromagnetism,
weak interactions, and
strong interactions. The
antiparticle of the up quark is the
up antiquark (sometimes called
antiup quark or simply
antiup), which differs from it only in that some of its properties have
equal magnitude but opposite sign.