Pseudovector meson
Encyclopedia
In high energy physics, a pseudovector meson or axial vector meson is a meson
Meson
In particle physics, mesons are subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometer: 10−15 m, which is about the size of a proton...

 with total spin 1 and even parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...

 (usually noted as JP=1+). Compare to a vector meson
Vector meson
In high energy physics, a vector meson is a meson with total spin 1 and odd parity . Compare to a pseudovector meson, which has a total spin 1 and even parity....

, which has a total spin 1 and odd parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...

.

The known pseudovector, or axial vector, mesons fall into two different classes; those with JPC=1+-, and those with JPC=1++. The first group have no spin excitation, but do have L=1. The latter group have both S=1 and L=1, with L and S coupling to J=1. The difference between the two groups gives them slightly different masses from the spin-orbit coupling rule. The h and b mesons are in the first group, and should have heavier masses according to the spin-orbit mass splitting; in practice, however, they do not appear to follow this rule in nature, as evidenced by the f and a mesons being heavier. There are considerable experimental uncertainties in pseudovector meson masses which will require additional experimental data to clarify.

The 1++ multiplet of light mesons may show similar behavior to that of the 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 cause generally reduced meson masses. Further experimentation is required in order to clarify the observed situation.

Pseudovector, or axial vector, mesons in the 1+- channel may most readily be seen in proton-antiproton annihilation and pion
Pion
In particle physics, a pion is any of three subatomic particles: , , and . Pions are the lightest mesons and they play an important role in explaining the low-energy properties of the strong nuclear force....

-nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

scattering. The mesons in the 1++ channel are normally seen in proton-proton and pion-nucleon scattering.

Examples

  • 1+- candidates: h1(1170), b1(1235), h1(1380)
  • 1++ candidates: f1(1285), a1(1260), f1(1420)
  • stranged candidates: K1(1270), K1(1400)
  • heavy candidates: hc, chic1
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