B flavour tagging using charm decays at the LHCb experiment

An algorithm is described for tagging the flavour content at production of neutral B mesons in the LHCb experiment. The algorithm exploits the correlation of the flavour of a B meson with the charge of a reconstructed secondary charm hadron from the decay of the other b hadron produced in the proton-proton collision. Charm hadron candidates are identified in a number of fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is calibrated on the self-tagged decay modes B ⁺ → J/ψK ⁺ and B ⁰ → J/ψK ^∗0 using 3:0fb. ^-1 of data collected by the LHCb experiment at pp centre-of-mass energies of 7TeV and 8TeV. Its tagging power on these samples of B → J/ψX decays is (0:30±0:01±0:01)%.