Measurement of the effective $B_s^0 \rightarrow K^{+}K^{-}$ Lifetime

Measurements of the $B_s^0 \rightarrow K^{+}K^{-}$ lifetime are presented using data collected by LHCb during 2010. The $B_s^0 \rightarrow K^{+}K^{-}$ lifetime can be used to put constraints on new physics contributions to the $B_s^0$ mixing phase and the width difference $\Delta \Gamma_s$ between light and heavy states in the $B_s^0$ system. Two independent lifetime fitting methods are used. One analysis makes a direct measurement of the lifetime, using a data driven approach to correct for the proper time bias introduced by the selection procedure. A complementary analysis cancels this proper time bias by making a measurement of the $B_s^0 \rightarrow K^{+}K^{-}$ lifetime relative to the better constrained $B^0$ lifetime. The results of the two measurements are in good agreement. The $B_s^0 \rightarrow K^{+}K^{-}$ lifetime is measured as $\tau_{B^0_s}$ = 1.440 $\pm$ 0.096 (stat) $\pm$ 0.010 (syst)ps