Measurement of the B_c Meson Lifetime Using B_c ->J/Psi e nu
  We present a measurement of the B_c+ meson lifetime in the semileptonic decay mode Bc+ ->J/Psi e+ nu using the CDF II detector at the Fermilab Tevatron Collider. From a sample of about 360pb-1 p-pbar collisions at sqrt(s)=1.96TeV, we reconstruct J/Psi e+ pairs with invariant mass in the kinematically allowed range 4<M(J/Psi e)<6GeV/c^2. A fit to the decay-length distribution of 238 signal events yields a measured Bc mesion lifetime 0.463 (+0.073,-0.065)+-0.036 ps. 
CDF Collaboration: A. Abulencia, et al