First observation of the doubly charmed baryon decay $Ξ_{cc}^{++}\rightarrow Ξ_{c}^{+}π^{+}$

Abstract

The doubly charmed baryon decay $Ξ_{cc}^{++} \rightarrow Ξ_{c}^{+} π^{+}$ is observed for the first time, with a statistical significance of $5.9σ$, confirming a recent observation of the baryon in the $Λ_c^{+} K^{-} π^{+} π^{+}$ final state. The data sample used corresponds to an integrated luminosity of $1.7\,\mathrm{fb}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of $13\mathrm{\,Te\kern -0.1em V}$. The $Ξ_{cc}^{++}$ mass is measured to be \begin{equation}\nonumber 3620.6\pm 1.5~(\text{stat})\pm 0.4~(\text{syst}) \pm 0.3~(Ξ_{c}^{+})~\text{MeV}/\it{c}^{2}, \end{equation} and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be \begin{equation}\nonumber \frac{\mathcal{B} (Ξ_{cc}^{++} \rightarrow Ξ_{c}^{+} π^{+}) \times \mathcal{B}(Ξ_{c}^{+} \rightarrow pK^{-}π^{+})} {\mathcal{B} (Ξ_{cc}^{++} \rightarrow Λ_c^{+} K^{-} π^{+} π^{+}) \times \mathcal{B}(Λ_c^{+} \rightarrow pK^{-}π^{+})} = 0.035\pm 0.009~(\text{stat}) \pm 0.003~(\text{syst}). \end{equation}

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-026.html