First observation of $\overline{B}\to D^{\left(*\right)}{\rho }^{\prime -},$ ${\rho }^{\prime -}\to \omega {\pi }^{-}$

We report on the observation of $\overline{B}\to D^{*}{\pi }^{+}{\pi }^{-}{\pi }^{-}{\pi }^0$ decays. The branching ratios for $D^{*+}$ and $D^{*0}$ are $(1.72\mathrm{}\pm 0.14\pm 0.24)\%$ and $(1.80\mathrm{}\pm 0.24\pm 0.27)\%,$ respectively. Each final state has a $D^{*}\omega {\pi }^{-}$ component, with branching ratios $(0.29\mathrm{}\pm 0.03\pm 0.04)\%$ and $(0.45\mathrm{}\pm 0.10\pm 0.07)\%$ for the $D^{*+}$ and $D^{*0}$ modes, respectively. We also observe $\overline{B}\to D\omega {\pi }^{-}$ decays. The branching ratios for $D^{+}$ and $D^0$ are $(0.28\mathrm{}\pm 0.05\pm 0.04)\%$ and $(0.41\mathrm{}\pm 0.07\pm 0.06)\%,$ respectively. A spin parity analysis of the $\omega {\pi }^{-}$ system in the $D\omega {\pi }^{-}$ final state shows a preference for a wide $1^{-}$ resonance. A fit to the $\omega {\pi }^{-}$ mass spectrum finds a central mass of $(1349\mathrm{}\pm {25}_{-5}^{+10\mathrm{}})$ MeV and width of $(547\mathrm{}\pm {86}_{-45}^{+46\mathrm{}})$ MeV. We identify this object as the $\rho \mathrm{}\left(1450\right)\mathrm{}$ or the ${\rho }^{\prime }.$