Search for the doubly charmed baryon $\hat{I}{ž}_{cc}^{+}$ in the $\hat{I}{ž}_c^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}$ final state

Abstract

A search for the doubly charmed baryon $\hat{I}{ž}_{cc}^{+}$ is performed in the $\hat{I}{ž}_c^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}$ invariant-mass spectrum, where the $\hat{I}{ž}_c^{+}$ baryon is reconstructed in the $p{K}^{-}\ddot{I}{€}^{+}$ final state. The study uses proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of 13$\mathrm{Te}\mathrm{V}$, 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}\mathrm{V}/c^2$. Upper limits are set on the ratio of branching fractions multiplied by the production cross-section with respect to the $\hat{I}{ž}_{cc}^{++}\to (\hat{I}{ž}_c^{+}\to p{K}^{-}\ddot{I}{€}^{+})\ddot{I}{€}^{+}$ decay for different $\hat{I}{ž}_{cc}^{+}$ mass and lifetime hypotheses in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 2.5 to 25$\mathrm{Ge}\mathrm{V}/c$. The results from this search are combined with a previously published search for the $\hat{I}{ž}_{cc}^{+}\to \hat{I}{›}_c^{+}{K}^{-}\ddot{I}{€}^{+}$ decay mode, yielding a maximum local significance of 4.0 standard deviations around the mass of 3620$\mathrm{Me}\mathrm{V}/c^2$, including systematic uncertainties. Taking into account the look-elsewhere effect in the 3.5$-$3.7$\mathrm{Ge}\mathrm{V}/c^2$ mass window, the combined global significance is 2.9 standard deviations including systematic uncertainties.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-019.html (LHCb public pages)