Search For Ξ_bc⁰ And Ω_bc⁰ Baryons Using Λ_c⁺π^-and Ξ_c⁺π^-Decay Modes In LHCb

A search for the doubly heavy baryons(?)bc0 and Ωbc0 is performed with the decay modes of(?)bc0(Ωbc0)→∧c+π-and(?)bc0(Ωbc0)→(?)c+π-using the proton-proton colli-sion data collected by the LHCb detector in 2016,2017,and 2018,corresponding to 5.8 fb-1 of integrated luminosity.In this analysis,the selection is developed with a blinded procedure.(?)bc0(Ωbc0)candidate is required to be in the signal region,where the reconstructed(?)bc0(Ωbc0)invariant mass between[6700,7200]MeV/c2.The background events are selected from the far upper side-band(SB)[7500,9000]MeV/c2 and the lower side-band[6000,6500]MeV/c2 of the data events,which is far from the(?)bc0(Ωbc0)signal region.We used the lower and upper side-band of signal candidates to study the offline se-lection,multi-variables selection(MVA)and background analysis.The ∧b0→∧c+π-((?)b0→(?)c+π-)decay is chosen as control channel.The signal yields of control chan-nels are determined by fitting the invariant mass distribution after event selections.We use Monte Carlo events to study efficiency and systematic uncertainties,includ-ing the geometrical acceptance of detector and generator level cuts efficiency,the combined reconstruction and selection efficiency,the trigger efficiency,and the PID efficiency for final state hadrons,the track efficiency and the MC-Match efficiency.These efficiencies are used to calculate the total efficiencies and efficiency ratios of signal to control channels.As there is no signal access in our data,upper limit on the branching fraction(BR)ratio relative to its control channel is estimated using the CLs method at 95%CL.