Measurement of the lifetime difference between B-s mass eigenstates

We present measurements of the lifetimes and polarization amplitudes for Bs0→J/ψφ and Bd0→J/ψK*0 decays. Lifetimes of the heavy and light mass eigenstates in the Bs0 system are separately measured for the first time by determining the relative contributions of amplitudes with definite CP as a function of the decay time. Using 203±15 Bs0 decays we obtain τL=(1.05-0.13+0.16±0.02) ps and τH=(2.07-0.46+0.58±0.03) ps. Expressed in terms of the difference ΔΓs and average Γs, of the decay rates of the two eigenstates, the results are ΔΓs/Γs=(65-33+25±1)% and ΔΓs=(0.47-0.24+0.19±0.01) ps-1.