Search for the doubly heavy baryons ${\Omega }_{bc}^0$ and ${\Xi }_{bc}^0$ decaying to ${\Lambda }_c^{+}{\pi }^{-}$ and ${\Xi }_c^{+}{\pi }^{-}$

The first search for the doubly heavy ${\Omega }_{bc}^0$ baryon and a search for ${\Xi }_{bc}^0$ baryon are performed using $pp$ collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of $13TeV$, corresponding to an integrated luminosity of 5.2$f{b}^{-1}$. The baryons are reconstructed via their decays to ${\Lambda }_c^{+}{\pi }^{-}$ and ${\Xi }_c^{+}{\pi }^{-}$. No significant excess is found for invariant masses between 6700 and 7300$MeV\mathrm{/}{c}^2$, in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20$GeV\mathrm{/}c$. Upper limits are set on the ratio of the ${\Omega }_{bc}^0$ and ${\Xi }_{bc}^0$ production cross-section times the branching fraction to ${\Lambda }_c^{+}{\pi }^{-}$ (${\Xi }_c^{+}{\pi }^{-}$) relative to that of the ${\Lambda }_b^0$ (${\Xi }_b^0$) baryon, for different lifetime hypotheses, at $95\mathrm{\%}$ confidence level. The upper limits range from $0.5\times {10}^{-4}$ to $2.5\times {10}^{-4}$ for the ${\Omega }_{bc}^0\to {\Lambda }_c^{+}{\pi }^{-}$ (${\Xi }_{bc}^0\to {\Lambda }_c^{+}{\pi }^{-}$) decay, and from $1.4\times {10}^{-3}$ to $6.9\times {10}^{-3}$ for the ${\Omega }_{bc}^0\to {\Xi }_c^{+}{\pi }^{-}$ (${\Xi }_{bc}^0\to {\Xi }_c^{+}{\pi }^{-}$) decay, depending on the considered mass and lifetime of the ${\Omega }_{bc}^0$ (${\Xi }_{bc}^0$) baryon.