Measurement of the Λb0 lifetime in Λb0 → Λc+ π- decays at the Collider Detector at Fermilab

The lifetime of the Λb0 baryon (consisting of u, d and b quarks) is the theoretically most interesting of all b-hadron lifetimes. The lifetime of Λb0 probes our understanding of how baryons with one heavy quark are put together and how they decay. Experimentally however, measurements of the Λb0 lifetime have either lacked precision or have been inconsistent with one another. This thesis describes the measurement of Λb0 lifetime in proton-antiproton collisions with center of mass energy of 1.96 TeV at Fermilab's Tevatron collider. Using 1070 ± 60pb-1 of data collected by the Collider Detector at Fermilab (CDF), a clean sample of about 3,000 fully-reconstructed Λb0 → Λc+π- decays (with Λc+ subsequently decaying via Λc+ → p+ K- π+) is used to extract the lifetime of the Λb0 baryon, which is found to be cτ(Λb0) = 422.8 ± 13.8(stat) ± 8.8(syst)(micro)m. This is the most precise measurement of its kind, and is even better than the current world average. It also settles the recent controversy regarding the apparent inconsistency between CDF's other measurement and the rest of the world.