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 = 1). Compare to a vector meson, which has a total spin 1 and odd parity.

The known pseudovector, or axial vector, mesons fall into two different classes; those with J = 1, and those with J = 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.