Study of $B^{0} \rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+}$ and $B^{0} \rightarrow D^{*-}K^{+}\pi^{-}\pi^{+}$ decays

Using proton-proton collision data collected by the LHCb experiment at $\sqrt{s} =$ 7 TeV, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, the ratio of branching fractions of the $B^{0}\rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+}$ decay relative to the $B^{0} \rightarrow D^{*-}\pi^{+}$ decay is measured to be \begin{equation*} \frac{\mathcal{B}(B^{0}\rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+})}{\mathcal{B}(B^{0} \rightarrow D^{*-}\pi^{+})} = 2.64 \pm 0.04\,(\text{stat.}) \pm 0.13\,(\text{syst.})\, . \label{eq:CF_BF_ratio_result} \end{equation*} The Cabibbo-suppressed decay $B^{0}\rightarrow D^{*-}K^{+}\pi^{-}\pi^{+}$ is observed for the first time and the measured ratio of branching fractions is \begin{equation*} \frac{\mathcal{B}(B^{0}\rightarrow D^{*-}K^{+}\pi^{-}\pi^{+})}{\mathcal{B}(B^{0} \rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+})} = (6.47 \pm 0.37\,(\text{stat.}) \pm 0.35\,(\text{syst.})) \times 10^{-2} \label{eq:CS_BF_ratio_result}\, . \end{equation*} A search for orbital excitations of charm mesons contributing to the $B^{0}\rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+}$ final state is also performed, and the first observation of the $B^{0}\rightarrow \bar{D}_{1}(2420)^{0}\pi^{+}\pi^{-}$ decay is reported with the ratio of branching fractions \begin{equation*} \frac{\mathcal{B}(B^{0}\rightarrow (\bar{D}_{1}(2420)^{0} \to D^{*-} \pi^{+}) \pi^{-}\pi^{+})}{\mathcal{B}(B^{0} \rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+})} = (2.04 \pm 0.42\,(\text{stat.}) \pm 0.22\,(\text{syst.})) \times 10^{-2}\, , \end{equation*} where the numerator represents a product of the branching fractions $\mathcal{B}(B^{0}\rightarrow \bar{D}_{1}(2420)^{0} \pi^{-} \pi^{+})$ and $\mathcal{B}(\bar{D}_{1}(2420)^{0} \to D^{*-} \pi^{+})$.