  Spin-parity analyses of the $\omega\pi$ system in the reaction $\gamma p \to
(\omega\pi) p$ for photon laboratory energies from 20 to 70 GeV have shown that
production of the $J^P=1^+$ $b_1(1235)$ meson dominates, with a $J^P=1^-$
background at the level of 20%. Using vector-meson dominance arguments, this
background is shown to be consistent with the data on $e^+e^- \to \omega\pi$.
The energy dependence of the data imply that the mechanism is a combination of
Reggeon and Pomeron exchange. Assuming that the latter is relevant only for the
$J^P = 1^-$ component and extrapolating to W=200 GeV, it is argued that this
accounts for most of the preliminary $\omega\pi$ signal observed by the H1
Collaboration in the same reaction. A residual peak can be ascribed to the
$b_1(1235)$, which requires a quark spin-flip from Pomeron exchange. Precisely
the same mechanism occurs in the reaction $\pi p \to a_1(1260) p$.

High Energy Physics - Phenomenology