Pseudovector meson

In high energy physics, a pseudovector meson or axial vector meson is a meson with total spin 1 and even parity (+) (usually noted as J^P = 1⁺ ).

Compare to a vector meson, which has a total spin 1 and odd parity (that is, J^P = 1⁻ ).

Charge parity (C) in addition to spatial parity (P)

The known pseudovector mesons fall into two different classes, all have even spatial parity ( P = "+" ), but they differ in another kind of parity called charge parity (C) which can be either even (+) or odd (−). The two types of pseudovector meson are:

those with odd charge parity J^PC = 1⁺⁻
those with even charge parity J^PC = 1⁺⁺

The 1⁺⁻ group has no intrinsic spin excitation ( S = 0 ), but do gain spin from angular momentum ( L = 1 ) of the orbits of the two constituent quarks around their mutual center. The second group (1⁺⁺) have both intrinsic spin S = 1 , and L = 1 , with L and S coupling to J = 1 .

Pseudovector, or axial vector, mesons in the 1⁺⁻ category are most readily be seen in proton‑antiproton annihilation and pion‑nucleon scattering. The mesons in the 1⁺⁺ category are normally seen in proton-proton and pion-nucleon scattering.

Discrepant mass estimates

The difference between the two groups gives them slightly different masses, from the spin‑orbit coupling rule. Theoretically, the h and b mesons are in the 1⁺⁻ group, and should have heavier masses, according to the spin-orbit mass splitting. However, the measured masses of the mesons do not appear to follow the rule, as evidenced by the f and a mesons being heavier. There are considerable uncertainties in experimental measurement of pseudovector mesons; more experimental data will be needed to confirm and accurately determine the discrepancy between theory and measurement.

The 1⁺⁺ multiplet of light mesons may show similar behavior to that of other vector mesons, in that the mixing of light quarks with strange quarks appears to be small for this quantum number. The 1⁺⁻ multiplet, on the other hand, may be affected by other factors that generally reduce meson masses. Again, further experimentation is required in order to solidify the observations.

Examples

rho meson
kaon-star meson
omega meson
1⁺⁻ candidates: h₁(1170), b₁(1235), h₁(1380)
1⁺⁺ candidates: f₁(1285), a₁(1260), f₁(1420)
strange candidates: K₁(1270), K₁(1400)
heavy candidates: h_c, χ_c1

Quarks	Up (quark antiquark) Down (quark antiquark) Charm (quark antiquark) Strange (quark antiquark) Top (quark antiquark) Bottom (quark antiquark)
Leptons	Electron Positron Muon Antimuon Tau Antitau Neutrino Electron neutrino Electron antineutrino Muon neutrino Muon antineutrino Tau neutrino Tau antineutrino

Bosons

Gauge	Photon Gluon W and Z bosons
Scalar	Higgs boson

Ghost fields

Faddeev–Popov ghosts

Hypothetical

Superpartners

Gauginos	Gluino Gravitino Photino
Others	Axino Chargino Higgsino Neutralino Sfermion (Stop squark)

Others

Composite

Hadrons

Baryons	Nucleon Proton Antiproton Neutron Antineutron Delta baryon Lambda baryon Sigma baryon Xi baryon Omega baryon
Mesons	Pion Rho meson Eta and eta prime mesons Bottom eta meson Phi meson J/psi meson Omega meson Upsilon meson Kaon B meson D meson Quarkonium
Exotic hadrons	Tetraquark (Double-charm tetraquark) Pentaquark