Search results
Results From The WOW.Com Content Network
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.
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.
A proton, the only baryon stable in isolation, has two up quarks and one down quark, confined via the exchange of gluons.. Baryons are composite particles made of three quarks, as opposed to mesons, which are composite particles made of an equal number of quarks and antiquarks.
mesons (b and c). The π − meson interacts with a nucleus in the emulsion at B. The π ± mesons have a mass of 139.6 MeV/c 2 and a mean lifetime of 2.6033 × 10 −8 s. They decay due to the weak interaction. The primary decay mode of a pion, with a branching fraction of 0.999877, is a leptonic decay into a muon and a muon neutrino:
Baryons, alongside mesons, are hadrons, composite particles composed of quarks. Quarks have baryon numbers of B = 1 / 3 and antiquarks have baryon numbers of B = − 1 / 3 . The term "baryon" usually refers to triquarks—baryons made of three quarks (B = 1 / 3 + 1 / 3 + 1 / 3 = 1).
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 ground state hybrid mesons 0 −+, 1 −+, 1 −−, and 2 −+ all lie a little below 2 GeV/c 2. The hybrid with exotic quantum numbers 1 −+ is at 1.9 ± 0.2 GeV/ c 2 . The best lattice computations to date are made in the quenched approximation , which neglects virtual quarks loops.