1.0% decrease in the number of events. Taking a conservative estimate of the systematic error due to the background shape we arrive at $\pm$5.5%.

The $\omega\pi^-$ System
------------------------

For all subsequent discussions we add the $D^o$ and $D^+$ final states together. We select sample of $\omega$’s in the $\pi^+\pi^-\pi^o$ mass window of 782$\pm$20 MeV using only combinations having $r<0.7$ in the Dalitz plot.

In Fig. \[m\_omega\_pi\] we show the $\omega\pi^-$ mass spectrum in the left-side plot. The solid histogram shows events from the lower $M_B$ sideband region (5.203 - 5.257 GeV) suitably normalized. The dotted histogram shows the background estimate from the $\Delta E$ sidebands, again normalized. In the signal distribution there is a wide structure around 1.4 GeV, that is inconsistent with background. We re-determine the $\omega\pi^-$ mass distribution by fitting the $M_B$ distribution in bins of $\omega\pi^-$ mass, and this is shown on the right-side. Fitting to a Breit-Wigner function, we find a peak value of 1415$\pm$43 MeV and a width of 419$\pm$110 MeV. It should be kept in mind that this particular signal shape is assumed to be correct. Other resonant or non-resonant contributions could affect the mass and width.

This structure appears identical to the one 