The reaction ${\pi }^{+}p\to {\pi }^{+}p\omega$ has been studied at 3.7 $\frac{\mathrm{GeV}}{c}$ using data from the LRL 72-in. hydrogen bubble chamber. An analysis of the $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ Dalitz plot for ∼ 4000 $\omega$ events yields no evidence for ${\pi }^{+}{\pi }^{-}{\pi }^0$ states with isospin $I\ne 0$ at the level of ${10}^{-3\mathrm{}}$ in intensity relative to the $I=0\mathrm{}$ intensity. A similar analysis of ∼ 500 $\omega$ events produced in a kinematical region of known $\rho -\omega$ coherence yields no evidence for ${\rho }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays with $I\ne 0$ at the 1% level in intensity relative to the ${\rho }^0\to {\pi }^{+}{\pi }^{-}$ mode. A significantly nonzero value of the charge asymmetry $\alpha =\frac{(N_{+}-N_{-})}{(N_{+}+N_{-})}$ is observed (0.179 ± 0.051) for $\omega$ events produced opposite a ${\Delta }^{++}$ (1236) in the narrow $t^{\prime }=|t-t_{min}|$ range [0.08 - 0.20 ${\left(\frac{\mathrm{GeV}}{c}\right)}^2$]. We discuss four possible origins for the observed interfering amplitude, whose quantum assignments may be deduced as $I^G=1^{-}$, $J^{\mathrm{PC}}=1^{-+}$: (1) $C$ violation in $\omega$ decay (which may be ruled out), (2) $C$ violation in ${\rho }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay, (3) a miscellaneous coherent background amplitude with these quantum numbers, and (4) a possible exotic resonant state with these quantum numbers.

Close

PrevNext

View figure in article