Optimization and calibration of the same-side kaon tagging algorithm using hadronic $B_{s}^{0}$ decays in 2011 data

We report on the optimization and calibration of the same-side kaon tagging algorithm using the decay $B_{s}^{0} \rightarrow D_{s}^{- \pi^{+}}$ with 1.0~$\mathrm{fb}^{-1}$ of data from the LHCb 2011 physics run. After a data-driven optimization and calibration, we measured an effective tagging efficiency for the same-side tagger of $(1.5\pm0.4)%$ using event-by-event predicted mistag for $B_{s}^{0} \rightarrow D_{s}^{- \pi^{+}}$ decays. For the combination of same-side kaon and opposite-side taggers the corresponding effective tagging efficiency is $(3.8\pm0.7)%$ using event-by-event predicted mistag in this channel.