Baryon number

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Flavour in particle physics
Flavour quantum numbers
Isospin: I or I3 Charm: C Strangeness: S Topness: T Bottomness: B′
Related quantum numbers
Baryon number: B Lepton number: L Weak isospin: T or T3 Electric charge: Q X-charge: X
Combinations
Hypercharge: Y Y = (B + S + C + B′ + T) Y = 2 (Q − I3) Weak hypercharge: YW YW = 2 (Q − T3) X + 2YW = 5 (B − L)
Flavour mixing
CKM matrix PMNS matrix Flavour complementarity
v t e

In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as

where ${\displaystyle n_{\rm {q}}}$ is the number of quarks, and ${\displaystyle n_{\rm {\overline {q}}}}$ 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.