Search for the doubly charmed baryon $\it{\Xi}_{cc}^{+}$ in the $\it{\Xi}_{c}^{+} \pi^{-} \pi^{+}$ final state

TL;DR

This paper reports a search for the doubly charmed baryon $ ext{ extit{Xi}}_{cc}^{+}$ in proton-proton collisions using LHCb data, setting upper limits on its production and combining results with previous searches, but finds no definitive signal.

Contribution

It provides the first combined analysis of multiple decay modes of $ ext{ extit{Xi}}_{cc}^{+}$, setting new upper limits and exploring its potential mass and lifetime.

Findings

No significant signal observed in the mass range 3.4-3.8 GeV/c^2.

Upper limits set on production cross-section ratios for various hypotheses.

Combined analysis yields a maximum local significance of 4.0 sigma, with a global significance of 2.9 sigma.

Abstract

A search for the doubly charmed baryon $\it{\Xi}_{cc}^{+}$ is performed in the $\it{\Xi}_{c}^{+} \pi^{-} \pi^{+}$ invariant-mass spectrum, where the $\it{\Xi}_{c}^{+}$ baryon is reconstructed in the $p K^{-} \pi^{+}$ final state. The study uses proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of 13$\mathrm{\,Te\kern -0.1em V}$, corresponding to a total integrated luminosity of 5.4$\,\mathrm{fb}^{-1}$. No significant signal is observed in the invariant-mass range of 3.4$-$3.8$\mathrm{\,Ge\kern -0.1em V}/c^2$. Upper limits are set on the ratio of branching fractions multiplied by the production cross-section with respect to the $\it{\Xi}_{cc}^{++} \rightarrow (\it{\Xi}_{c}^{+} \rightarrow p K^{-} \pi^{+}) \pi^{+}$ decay for different $\it{\Xi}_{cc}^{+}$ mass and lifetime hypotheses in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 2.5 to 25$\mathrm{\,Ge\kern -0.1em V}/c$. The results from this search are combined with a previously published search for the $\it{\Xi}_{cc}^{+} \rightarrow \it{\Lambda}_{c}^{+} K^{-} \pi^{+}$ decay mode, yielding a maximum local significance of 4.0 standard deviations around the mass of 3620$\mathrm{\,Me\kern -0.1em V}/c^2$, including systematic uncertainties. Taking into account the look-elsewhere effect in the 3.5$-$3.7$\mathrm{\,Ge\kern -0.1em V}/c^2$ mass window, the combined global significance is 2.9 standard deviations including systematic uncertainties.