Using Double Tagging to measure the Performance of the Same Side Kaon Tagger in Data

This note describes a method for the measurement of the wrong-tag fraction of the Same Side Kaon tagger, $\omega_{ss}$ in data using the Double Tagging procedure. The importance of such a measurement is explained and the method of Double Tagging described. This measurement was carried out using samples from reconstructed $Bs -> Ds\pi$ and $Bs -> Ds\mu\nu$ decays. The impact of background in both decay channels on the measurement of $\omega_{ss}$ was also studied. A general way of handling tagger correlations is presented. Finally, the Double Tagging measurement and the correlation investigation are performed on the present Monte Carlo data and the results presented. Results show that with 2fb-1 of data, the Double Tagging procedure can be used to measure the SS Kaon wrong-tag fraction to a statistical accuracy of 3.6% and 1.2% for the $Bs -> Ds\pi$ and $Bs -> Ds\mu\nu$ channels respectively.