Measurement of the $\Lambda^0_b$ Lifetime in $\Lambda^0_b \to J/\psi \Lambda^0$ in $p\bar{p}$ Collisions at $\sqrt{s}$ = 1.96 TeV

We report a measurement of the $\lambdab$ lifetime in the exclusive decay $\lambdabjpsilm$ in $p \overline{p}$ collisions at $\sqrt{s} = 1.96~{\rm TeV}$ using an integrated luminosity of 1.0 ${\rm fb}^{-1}$ of data collected by the CDF II detector at the Fermilab Tevatron. Using fully reconstructed decays, we measure $\tau(\lambdab) = 1.593 ~^{+0.083}_{-0.078} ~({\rm stat.}) \pm 0.033~{\rm (syst.)~ps}$. This is the single most precise measurement of $\tau(\lambdab)$ and is 3.2 $\sigma$ higher than the current world average.