First observation of $\hat{I}{›}_b^0\to \hat{I}{\pounds }_c^{(\ast )++}{D}^{(\ast )-}{K}^{-}$ decays

Abstract

The four decays, $\hat{I}{›}_b^0\to \hat{I}{\pounds }_c^{(\ast )++}{D}^{(\ast )-}{K}^{-}$, are observed for the first time using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of $13\mathrm{TeV}$, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$. By considering the $\hat{I}{›}_b^0\to \hat{I}{›}_c^{+}{\overline{D}}^0{K}^{-}$ decay as reference channel, the following branching fraction ratios are measured to be $$\frac{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{++}{\mathrm{D}}^{-}{\mathrm{K}}^{-})}{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{›}_c^{+}{\overline{\mathrm{D}}}^0{\mathrm{K}}^{-})}=0.282\pm 0.016\pm 0.016\pm 0.005,\frac{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{\ast ++}{\mathrm{D}}^{-}{\mathrm{K}}^{-})}{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{++}{\mathrm{D}}^{-}{\mathrm{K}}^{-})}=0.460\pm 0.052\pm 0.028,\frac{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{++}{\mathrm{D}}^{\ast -}{\mathrm{K}}^{-})}{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{++}{\mathrm{D}}^{-}{\mathrm{K}}^{-})}=2.261\pm 0.202\pm 0.129\pm 0.046,\frac{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{\ast ++}{\mathrm{D}}^{\ast -}{\mathrm{K}}^{-})}{\mathcal{B}(\hat{\mathcal{I}}{›}_b^0\to \hat{\mathcal{I}}{\pounds }_c^{++}{\mathrm{D}}^{-}{\mathrm{K}}^{-})}=0.896\pm 0.137\pm 0.066\pm 0.018,$$ where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more data set to become available following the LHCb upgrade.

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-2023-044.html (LHCb public pages)