Precise measurement of the B hadron lifetime play an important role in non-perturbative aspect of QCD. My talk is based on the measurement done by CMS with the Run1 data. In neutral Bs meson, we observe a sizeable mass difference due to its particle and antiparticle oscillation. Precise measurement of the mixing phase and dgamma can give a signature of beyond Standard model of physics.
In this talk, I will present the published results on the dgamma  measurement at CMS experiment using Run1 data.