Observation of $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ decays

TL;DR

This paper reports the first observation of specific $ ext{Lambda}_b^0$ baryon decays into multihadron final states, measuring their branching ratios with data from the LHCb detector at CERN.

Contribution

The study provides the first measurements of branching fractions for $ ext{Lambda}_b^0$ decays into $D^+ p \pi^-\pi^-$ and $D^{*+} p \pi^-\pi^-$, using a normalization channel and detailed ratio calculations.

Findings

First observation of the decay modes.

Branching ratio for $ ext{Lambda}_b^0 o D^+ p \pi^-\pi^-$ is (5.35 ± 0.21 ± 0.16)%.

Branching ratio for $ ext{Lambda}_b^0 o D^{*+} p \pi^-\pi^-$ relative to $ ext{Lambda}_b^0 o D^+ p \pi^-\pi^-$ is (61.3 ± 4.3 ± 4.0)%.

Abstract

The multihadron decays $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ are observed in data corresponding to an integrated luminosity of 3fb$^{-1}$, collected in proton-proton collisions at centre-of-mass energies of 7 and 8TeV by the LHCb detector. Using the~decay $\Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^-$ as a normalisation channel, the ratio of branching fractions is measured to be $$ \frac { {\mathcal{B}} ( \Lambda_b^0\rightarrow D^+ p \pi^-\pi^- ) } { {\mathcal{B}} ( \Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^- ) } \times \frac { {\mathcal{B}} ( D^+ \rightarrow K^-\pi^+\pi^+) } { {\mathcal{B}} ( \Lambda_c^+ \rightarrow p K^-\pi^+ ) } = ( 5.35 \pm 0.21 \pm 0.16 ) \% \,, $$ where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ decays is found to be $$ \frac{ {\mathcal{B}} ( \Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^- )} { {\mathcal{B}} ( \Lambda_b^0\rightarrow D^{+} p \pi^-\pi^- )} \times ( {\mathcal{B}}( D^{*+} \rightarrow \pi^0 ) + {\mathcal{B}}( D^{*+} \rightarrow \gamma )) = ( 61.3 \pm 4.3 \pm 4.0 ) \% \,. $$