  A measurement of the Lambda_b lifetime and mass in the decay channel Lambda_b
-> J/psi(mu^+ mu^-) Lambda^0(p pi^-) is presented. The analysis uses a signal
sample of about 2200 Lambda_b and anti-Lambda_b decays that are reconstructed
in 4.9 fb^-1 of ATLAS pp collision data collected in 2011 at the LHC
center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum
likelihood fit is used to extract the Lambda_b lifetime and mass. They are
measured to be tau(Lambda_b) = 1.449 +/- 0.036(stat) +/- 0.017(syst) ps and
m(Lambda_b) = 5619.7 +/- 0.7(stat) +/- 1.1(syst) MeV.
