Vector meson

The vector mesons contrast with the pseudovector mesons, which also have a total spin 1 but instead have even parity. The vector and pseudovector mesons are also dissimilar in that the spectroscopy of vector mesons tends to show nearly pure states of constituent quark flavors, whereas pseudovector mesons and scalar mesons tend to be expressed as composites of mixed states.

Uniquely pure flavor states

Since the development of the quark model by Murray Gell-Mann (and also independently by George Zweig), the vector mesons have demonstrated the spectroscopy of pure states. The fact that the I = 1 rho meson (ρ) and I = 0 omega meson (ω) have nearly equal mass centered on 770–780 MeV/c², while the phi meson (φ) has a higher mass around 1020 MeV/c², indicates that the light-quark vector mesons appear in nearly pure states, with the φ meson having a nearly 100 percent amplitude of hidden strangeness.

These nearly pure states characteristic of the vector mesons are not at all evident in the pseudoscalar meson or scalar meson multiplets, and may be only slightly realized among the tensor meson and pseudovector meson multiplets. This fact makes the vector mesons an excellent probe of the quark flavor content of other types of mesons, measured through the respective decay rates of non-vector mesons into the different types of vector mesons. Such experiments are very revealing for theorists who seek to determine the flavor content of mixed state mesons.