Spin-parity analysis of theBmeson

We have done a $J^P$ analysis of the low-mass ${\pi }^{+}\omega$ system, using the reaction ${\pi }^{+}p\to {\pi }^{+}\omega p$ at 7.1 GeV/c. We find that the $B$ resonance cannot be $J^P=0^{-}$ and must belong to the unnatural-parity series ($1^{+}$, $2^{-}$, $3^{+}$,...), regardless of the amount of interference between the $B$ and the background. If we assume that the $B$ does not interfere with the background, we find that all $J^P$ states for the resonance are rejected except for $1^{+}$. Even if interference effects are allowed in the analysis, a good fit with reasonable parameters is obtained only with the $1^{+}$ hypothesis for the $B$ meson. In an appendix, we give relevant theoretical formulas appropriate for a $\pi \omega$ system with any number of spin-parity states and arbitrary degrees of interference among them.