First observation of the rare $B^{+}\to D^{+} K^{+} \pi^{-}$ decay

TL;DR

This paper reports the first observation of the rare decay $B^{+} o D^{+} K^{+} \pi^{-}$ with a significant signal, measures its branching fraction, and investigates possible intermediate resonant contributions, setting upper limits where no signals are found.

Contribution

The paper provides the first experimental observation and measurement of the branching fraction for the decay $B^{+} o D^{+} K^{+} \pi^{-}$ and searches for related quasi-two-body decays.

Findings

Decay observed with 8 sigma significance

Branching fraction measured as (5.31 ± 0.90 ± 0.48 ± 0.35)×10^{-6}

No significant signals for intermediate resonances

Abstract

The $B^{+}\to D^{+} K^{+} \pi^{-}$ decay is observed in a data sample corresponding to $3.0\,{\rm fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is $8\,\sigma$ and the branching fraction is measured to be ${\cal B}\left(B^{+}\to D^{+} K^{+} \pi^{-}\right) = (5.31 \pm 0.90 \pm 0.48 \pm 0.35)\times 10^{-6}$, where the uncertainties are statistical, systematic and due to the normalisation mode $B^{+}\to D^{-} K^{+} \pi^{+}$, respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from $B^{+}\to D^{*}_{2}(2460)^{0}K^{+}$ and $B^{+}\to D^{+} K^{*}(892)^{0}$ decays. No significant signals are observed and upper limits are set on their branching fractions.