Observation of the $B^{+}\to {D^{*}}^{-}{K}^{+}{\pi }^{+}$ decay

The $B^{+}\to {D^{*}}^{-}{K}^{+}{\pi }^{+}$ decay potentially provides an excellent way to investigate charm meson spectroscopy. The decay is searched for in a sample of proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$. A clear signal is observed, and the ratio of its branching fraction to that of the $B^{+}\to D^{*-}{\pi }^{+}{\pi }^{+}$ normalization channel is measured to be $\mathcal{B}(B^{+}\to D^{*-}{K}^{+}{\pi }^{+})/\mathcal{B}(B^{+}\to D^{*-}{\pi }^{+}{\pi }^{+})=(6.39\pm 0.27\pm 0.48)\times {10}^{-2},$ where the first uncertainty is statistical and the second is systematic. This is the first observation of the $B^{+}\to {D^{*}}^{-}{K}^{+}{\pi }^{+}$ decay.

Figure 1

Leading diagram for $B^{+}\to D^{*-}{K}^{+}{\pi }^{+}$ and $D^{*-}{\pi }^{+}{\pi }^{+}$ decays, where the $D^{*-}{\pi }^{+}$ system is produced through the decay of an excited charm state denoted ${\overline{D}}^{**0}$.

Figure 2

Fits to $B$ candidate mass distributions for (left) $D^{*-}{K}^{+}{\pi }^{+}$ and (right) $D^{*-}{\pi }^{+}{\pi }^{+}$ samples with (top) linear and (bottom) logarithmic $y$-axis scales. The individual components are (solid blue) total fit function, (dashed green) signal shape, (long-dashed violet) combinatorial background, (dot dashed red) partially reconstructed background and (double-dot dashed orange) $D^{*-}{\pi }^{+}{\pi }^{+}$ to $D^{*-}{K}^{+}{\pi }^{+}$ cross-feed.

Figure 3

Background-subtracted [36] and efficiency-corrected $m(D^{*-}{\pi }^{+})$ distribution from $B^{+}\to D^{*-}{K}^{+}{\pi }^{+}$ decays. The grey dashed line illustrates a phase-space distribution, normalized to the same number of weighted candidates.