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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.
Because quarks have a spin 1 / 2 , the difference in quark number between mesons and baryons results in conventional two-quark mesons being bosons, whereas baryons are fermions. Each type of meson has a corresponding antiparticle (antimeson) in which quarks are replaced by their corresponding antiquarks and vice versa.
Mesons named with the letter "f" are scalar mesons (as opposed to a pseudo-scalar meson), and mesons named with the letter "a" are axial-vector mesons (as opposed to an ordinary vector meson) a.k.a. an isoscalar vector meson, while the letters "b" and "h" refer to axial-vector mesons with positive parity, negative C-parity, and quantum numbers I G of 1 + and 0 − respectively.
Baryons and mesons are both hadrons, which are particles composed solely of quarks or both quarks and antiquarks. The term baryon is derived from the Greek "βαρύς" ( barys ), meaning "heavy", because, at the time of their naming, it was believed that baryons were characterized by having greater masses than other particles that were classed ...
Mesons are hadrons with zero baryon number. If the quark–antiquark pair are in an orbital angular momentum L state, and have spin S, then | L − S | ≤ J ≤ L + S, where S = 0 or 1, P = (−1) L+1, where the 1 in the exponent arises from the intrinsic parity of the quark–antiquark pair. C = (−1) L+S for mesons which have no flavor.
The baryon number of all mesons is, indeed, zero. The square roots in the quark content are just normalization factors . MuDavid ( talk ) 14:58, 8 June 2010 (UTC) [ reply ]
Kaon; Composition: K + u s. K 0 d s. K − s u: Statistics: Bosonic: Family: Mesons: Interactions: Strong, weak, electromagnetic, gravitational: Symbol: K + K 0 K −: Antiparticle: K + K −. K 0 K 0. K − K +: Discovered: 1947 (Clifford Butler and George Rochester at Department of Physics and Astronomy, University of Manchester)
Significantly, the X and Y bosons couple quarks (constituents of protons and others) to leptons (such as positrons), allowing violation of the conservation of baryon number thus permitting proton decay. However, the Hyper-Kamiokande has put a lower bound on the proton's half-life as around 10 34 years. [2]