# {Measurement of Lifetime and Decay-Width Difference in $B^0_s \to J/\psi \phi$ Decays}

We measure the mean lifetime ${\tau=2/(\Gamma_L+\Gamma_H)}$ and the decay-width difference ${\Delta\Gamma=\Gamma_L-\Gamma_H}$ of the light and heavy mass eigenstates of the ${B_s^0}$ meson, ${B_{sL}^0}$ and ${B_{sH}^0}$, in ${B_s^0\to J/\psi\phi}$ decays using 1.7 fb-1 of data collected with the CDF II detector at the Fermilab Tevatron $p\bar{p}$ collider. Assuming CP conservation, a good approximation for the ${B_s^0}$ system in the standard model, we obtain ${\Delta\Gamma=0.076_{-0.063}^{+0.059}}$(stat)$\pm 0.006$(syst) ps-1 and $\tau=1.52\pm 0.04$(stat)$\pm 0.02$(syst) ps, the most precise measurements to date. Our constraints on the weak phase and ${\Delta\Gamma}$ are consistent with CP conservation.

### Cited Authors

• Aaltonen, ; T, ; others,

• 2008

### Published In

• Phys. Rev. Lett.

• 100 /

• 121803 -

• 18517856