Search for the doubly heavy $$ {\Xi}_{bc}^0 $$ baryon via decays to D0pK−

A search for the doubly heavy $ {\Xi}_{bc}^0 $ baryon using its decay to the D$^{0}$pK$^{–}$ final state is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb$^{−1}$. No significant signal is found in the invariant mass range from 6.7 to 7.2 GeV/c$^{2}$. Upper limits are set at 95% credibility level on the ratio of the $ {\Xi}_{bc}^0 $ production cross-section times its branching fraction to D$^{0}$pK$^{−}$ relative to that of the $ {\Lambda}_b^0\to {D}^0{pK}^{-} $ decay. The limits are set as a function of the $ {\Xi}_{bc}^0 $ mass and lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and in the transverse momentum region from 5 to 25 GeV/c. Upper limits range from 1.7 × 10$^{−2}$ to 3.0 × 10$^{−1}$ for the considered $ {\Xi}_{bc}^0 $ mass and lifetime hypotheses.[graphic not available: see fulltext]