Measurement of the B̄s0 effective lifetime in the J/ψf <inf>0</inf>(980) final state

The effective lifetime of the B̄s0 meson in the decay mode B̄s0→J/ψf ₀(980) is measured using 1.0fb ^-1 of data collected in pp collisions at √s=7TeV with the LHCb detector. The result is 1.700±0.040±0.026ps, where the first uncertainty is statistical and the second systematic. As the final state is CP-odd, and CP violation in this mode is measured to be small, the lifetime measurement can be translated into a measurement of the decay width of the heavy B̄s0 mass eigenstate, Γ _H=0.588±0.014±0.009ps ^-1.