we allow the shape, $p_2$, to vary (the normalization, $p_1$, was already allowed to vary). This results in 3.8% increase in the number of events. Finally, we choose a different background function $$back'(r)=p_1 r\sqrt{1-r^2}\left(1+p_2 r + p_3 r^2 +p_4 r^3 
\right)~~~,$$ and repeat the fitting procedure. This results in a 3.7% decrease in the number of events. Taking a conservative estimate of the systematic error due to the background shape we arrive at $\pm$3.8%. We use the current particle data group values for the relevant $D^{*+}$ and $D^o$ branching ratios of (68.3$\pm$1.4)% ($D^{*+}\to\pi^+ D^o$) and (3.85$\pm$0.09)% ($D^o\to K^-\pi^+$), respectively [@PDG]. The relative errors, 2.0% for the $D^{*+}$ branching ratio and 2.3% for the $D^o$ are added in quadrature to the other sources of systematic error, yielding a total systematic error of 10%.

We wish to search for narrow structures. However, we cannot fit the $B$ mass spectrum in small $(4\pi)^-$ mass intervals due to a lack of statistics. Thus we plot the $(4\pi)^-$ mass for events in the $M_B$ peak for the $D^o\to K^-\pi^+$ mode and the sum of all three modes in Fig. \[m4pi\_c\_all\]. We also plot two background samples: events at lower $M_B$ (5.203 - 5.257 GeV) and 