Measurement of the Lambda(B) lifetime in the decay mode Lambda(b) decaying to Jpsi-Lambda

This thesis describes a measurement of the Λ_B(5624) lifetime in the exclusive decay mode Λ_b → J/ψΛ, with J/ψ → μ +μ− and Λ → p +π−. This is the first measurement of the Λ _B lifetime in a mode where the Λ_B is fully reconstructed. As a control sample, we use the decay mode B0 → J/ψ$K0s$, with J/ψ → μ+μ − and $K0s$ → π+π−.; We obtain 46 ± 9 Λ_B and 256 ± 15 B0 candidate decays in 65 pb −1 of pp¯ collision data collected by the CDF II experiment at Fermilab. We obtain the value tLB =1.25±0.26stat.± 0.14syst.ps. ...