First observation of the $\mathit{\Lambda}_b^{0}\!\rightarrow\mathit{\Lambda}_{c}^{+}D_{s}^{-}K^{+}K^{-}$ decay and search for pentaquarks in the $\mathit{\Lambda}_{c}^{+}D_{s}^{-}$ system

TL;DR

This paper reports the first observation of a specific decay mode of the Lambda_b^0 baryon, measures its branching ratio, and searches for exotic pentaquark states in the decay products, setting upper limits on their production.

Contribution

The study provides the first observation of the Lambda_b^0 to Lambda_c^+ D_s^- K^+ K^- decay and sets constraints on hidden-charm pentaquarks with strangeness in the Lambda_c^+ D_s^- system.

Findings

First observation of the decay mode with a measured branching ratio

No evidence found for the pentaquarks, upper limits set

Quantitative constraints on pentaquark production ratios

Abstract

The $\mathit{\Lambda}_b^{0}\!\rightarrow\mathit{\Lambda}_{c}^{+}D_{s}^{-}K^{+}K^{-}$ decay is observed for the first time using the data sample from proton-proton collisions recorded at a center-of-mass energy of $13\,\text{TeV}$ with the LHCb detector, corresponding to an integrated luminosity of $6\,\text{fb}^{-1}$. The ratio of branching fraction to that of $\mathit{\Lambda}_b^{0} \!\rightarrow\mathit{\Lambda}_{c}^{+}D_{s}^{-}$ decays is measured as $0.0141 \pm 0.0019 \pm 0.0012$, where the first uncertainty is statistical and the second systematic. A search for hidden-charm pentaquarks with strangeness is performed in the $\mathit{\Lambda}_{c}^{+}D_{s}^{-}$ system. No evidence is found, and upper limits on the production ratio of $P_{c\bar{c}s}(4338)^0$ and $P_{c\bar{c}s}(4459)^0$ pentaquarks relative to the $\mathit{\Lambda}_{c}^{+}D_{s}^{-}$ final state are set at the $95\%$ confidence level as $0.12$ and $0.20$, respectively.