Measurement Of The Lambda0b Lifetime In Lambda0b 2lambda Cpi Decays At The Collider Detector At Fermilab

Measurement of the [Lambda]0b Lifetime in [Lambda]0b 2![Lambda]+c[pi]- Decays at the Collider Detector at Fermilab

The lifetime of the [Lambda]0b baryon (consisting of u, d and b quarks) is the theoretically most interesting of all b-hadron lifetimes. The lifetime of [Lambda]0b probes our understanding of how baryons with one heavy quark are put together and how they decay. Experimentally however, measurements of the [Lambda]0b lifetime have either lacked precision or have been inconsistent with one another. This thesis describes the measurement of [Lambda]0b 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 [Lambda]0b →[Lambda]c+[pi]- decays (with [Lambda]+c subsequently decaying via [Lambda]+c → p+ K- [pi]+) is used to extract the lifetime of the [Lambda]0b baryon, which is found to be c[tau]([Lambda]0b) = 422.8 ± 13.8(stat) ± 8.8(syst)[mu]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.

Measurement of the $\Lambda^0_b$ Lifetime in the Exclusive Decay $\Lambda^0_b \rightarrow J/\psi \Lambda^0$ with the \D0~detector

In this work we report a measurement of the [Lambda]0b baryon lifetime using the exclusive decay [Lambda]0b→ J/ [Psi][Lambda]0. The B0 meson lifetime is also measured in the topologically similar channel B0→ J/ K0S , which provides a crosscheck of the measurement procedure, and allows a direct determination of the ratio of the [Lambda]0b and the B0 lifetimes. The data used in this analysis were collected with the DØ detector during the complete Run II of the Fermilab Tevatron Collider, from 2002 to 2011, and correspond to an integrated luminosity of 10.4 fb-1 of proton-antiproton collisions at a center of mass energy √s = 1.96 TeV. We obtain [tau] ([Lambda]0b ) = 1.303 ± 0.075 (stat.) ± 0.035 (syst.) ps, [tau] (B0) = 1.508±0.025 (stat.)±0.043 (syst.) ps and [tau] ([Lambda]0b )/[tau] (B0) = 0.864± 0.052 (stat.)±0.033 (syst.). These measurements supersede previous results of the DØ Collaboration using the same decay channels. Our measurement of the lifetime ratio is in excellent agreement with theoretical predictions and compatible with the current world-average, but differs with the latest measurement of the CDF Collaboration in more than 2 standard deviations.

Measurement of the B0s Lifetime Using Semi-leptonic Decays with the Collider Detector at Fermilab