Quantum number relating the quantity of quarks and antiquarks in a system
In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as
where
is the number of
quarks, and
is the number of
antiquarks.
Baryons (three quarks) have a baryon number of +1,
mesons (one quark, one antiquark) have a baryon number of 0, and antibaryons (three antiquarks) have a baryon number of −1.
Exotic hadrons like
pentaquarks (four quarks, one antiquark) and
tetraquarks (two quarks, two antiquarks) are also classified as baryons and mesons depending on their baryon number.