Measurement of the $bar{B}_s^0to D_s^-D_s^+$ and $bar{B}_s^0to D^-D_s^+$ effective lifetimes

The first measurement of the effective lifetime of the $bar{B}_s^0$ meson in the decay $bar{B}_s^0to D_s^-D_s^+$ is reported using a proton-proton collision dataset, corresponding to an integrated luminosity of 3 fb$^{-1}$, collected by the LHCb experiment. The measured value of the $bar{B}_s^0to D_s^-D_s^+$ effective lifetime is $1.379pm0.026pm0.017$ ps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light $bar{B}_s^0$ mass eigenstate of Gamma_L$=0.725pm0.014pm0.009$ ps$^{-1}$. The $bar{B}_s^0$ lifetime is also measured using the flavor-specific $bar{B}_s^0to D^-D_s^+$ decay to be $1.52pm0.15pm0.01 {rm ps}$.