Measurement Of The Lambda 0b Lifetime In Lambda 0b 2 Lambda C Pi 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.

Radiation and Detectors

This textbook provides an introduction to radiation, the principles of interaction between radiation and matter, and the exploitation of those principles in the design of modern radiation detectors. Both radiation and detectors are given equal attention and their interplay is carefully laid out with few assumptions made about the prior knowledge of the student. Part I is dedicated to radiation, broadly interpreted in terms of energy and type, starting with an overview of particles and forces, an extended review of common natural and man-made sources of radiation, and an introduction to particle accelerators. Particular attention is paid to real life examples, which place the types of radiation and their energy in context. Dosimetry is presented from a modern, user-led point of view, and relativistic kinematics is introduced to give the basic knowledge needed to handle the more formal aspects of radiation dynamics and interaction. The explanation of the physics principles of interaction between radiation and matter is given significant space to allow a deeper understanding of the various technologies based on those principles. Following an introduction to the ionisation mechanism, detectors are introduced in Part II, grouped according to the physical principle that underpins their functionality, with chapters covering gaseous detectors, semiconductor detectors, the scintillation process and light detectors. The final two chapters describe the phenomenology of showers and the design of calorimeters, and cover additional phenomena including Cherenkov and transition radiation and the detection of neutrinos. An appendix offers the reader a useful review of statistics and probability distributions. The mathematical formalism is kept to a minimum throughout and simple derivations are presented to guide the reasoning and facilitate understanding of the working principles. The book is unique in its wide scope and introductory level, and is suitable for undergraduate and graduate students in physics and engineering. The reader will acquire an awareness of how radiation and its exploitation are becoming increasingly relevant in the modern world, with over 140 experimental figures, detector schematics and photographs helping to relate the material to a broader research context.

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