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

## TL;DR

This paper reports the first observation of the decay $B^+ o D^{*-}K^+ o ext{pi}^+ ext{pi}^- ext{pi}^+$, measuring its branching ratio relative to a similar decay, using LHCb data at 7 and 8 TeV.

## Contribution

The paper presents the first observation of the $B^+ o D^{*-}K^+ ext{pi}^+$ decay and measures its branching fraction ratio using proton-proton collision data.

## Key findings

- First observation of the decay $B^+ o D^{*-}K^+ ext{pi}^+$.
- Measured branching fraction ratio: (6.39 ± 0.27 ± 0.48) × 10^{-2}.
- Data collected at 7 and 8 TeV with 3 fb^{-1} luminosity.

## Abstract

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 centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3~{\rm fb}^{-1}$. A clear signal is observed, and the ratio of its branching fraction to that of the $B^+ \to D^{*-}\pi^+\pi^+$ normalisation channel is measured to be \begin{equation*} \frac{\mathcal{B}(B^+ \to D^{*-}K^+\pi^+)}{\mathcal{B}(B^+ \to D^{*-}\pi^+\pi^+)} = \left( 6.39 \pm 0.27 \pm 0.48 \right) \times 10^{-2} \, , \end{equation*} where the first uncertainty is statistical and the second is systematic. This is the first observation of the $B^+ \to D^{*-}K^+\pi^+$ decay.