The
down quark or
d quark (symbol: d) is the second-lightest of all
quarks, a type of
elementary particle, and a major constituent of
matter. Together with the
up quark, it 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 . Like all
quarks, the down quark is an
elementary fermion with
spin-, and experiences all four
fundamental interactions:
gravitation,
electromagnetism,
weak interactions, and
strong interactions. The
antiparticle of the down quark is the
down antiquark (sometimes called
antidown quark or simply
antidown), which differs from it only in that some of its properties have
equal magnitude but opposite sign.