Heavy Quark Physics On The Lattice With Improved Nonrelativistic Actions
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Heavy Quark Physics on the Lattice with Improved Nonrelativistic Actions
Hadrons containing heavy quarks, in particular b quarks, play an important role in high energy physics. Measurements of their electroweak interactions are used to test the Standard Model and search for new physics. For the comparison of experimental results with theoretical predictions, nonperturbative calculations of hadronic matrix elements within the theory of quantum chromodymanics are required. Such calculations can be performed from first principles by formulating QCD on a Euclidean spacetime grid and computing the path integral numerically. Including b quarks in lattice QCD calculations requires special techniques as the lattice spacing in present computations usually can not be chosen fine enough to resolve their Compton wavelength. In this work, improved nonrelativistic lattice actions for heavy quarks are used to perform calculations of the bottom hadron mass spectrum and of form factors for heavy-to-light decays. In heavy-to-light decays, additional complications arise at high recoil, when the momentum of the light meson reaches a magnitude comparable to the cutoff imposed by the lattice. Discretisation errors at high recoil can be reduced by working in a frame of reference where the heavy and light mesons move in opposite directions. Using a formalism referred to as moving nonrelativistic QCD (mNRQCD), the nonrelativistic expansion for the heavy quark can be performed around a state with an arbitrary velocity. This dissertation begins with a review of the fundamentals of lattice QCD. Then, the construction of effective Lagrangians for heavy quarks in the continuum and on the lattice is discussed in detail. A highly improved lattice mNRQCD action is derived and its effectiveness is demonstrated by nonperturbative tests involving both heavy-heavy and heavy-light mesons at several frame velocities. This mNRQCD action is then used in combination with a staggered action for the light quarks to calculate hadronic matrix elements relevant for rare B decays, including B --> K* gamma and B --> K l l. A major contribution to the uncertainty of the results also comes from statistical errors. The effectiveness of random-wall sources to reduce these errors is studied. As another application of a nonrelativistic heavy quark action, the spectrum of bottomonium is calculated and masses of several bottom baryons are predicted. In these computations, the light quarks are implemented with a domain wall action.
Heavy Flavour Physics
The lectures collected in this book present a comprehensive review of the current knowledge of heavy-quark physics, from the points of view of both theory and experiment. Heavy Flavour Physics has accomplished enormous progress during the last few years: the last heavy quark has been discovered and the quality of the collected data on the other relatively lighter quarks has dramatically improved. On the theory side, noticeable progress has been reported on new calculations of decay rates based on various techniques, such as QCD sum rules, heavy-quark mass expansion and lattice QCD. The theory of heavy quark production is constantly improving and awaiting new results. Nevertheless there are strong reasons to believe that the Standard Model of High Energy Physics is incomplete. It exhibits very peculiar patterns for which it offers no explanation. The basic constituents of matter are arranged into three seemingly identical generations or families of quarks and leptons, differing merely in their masses. The pattern in the fermion masses, why they are families and why there are three of them is not yet understood. Furthermore it is known that at least within the standard model there is an intimate connection between the replication of families and the gateway of CP violation, in addition, the latter phenomenon is a crucial ingredient in explaining why our universe is made up almost exclusively of matter rather than being more or less matter-antimatter symmetric. How and to what extent can Heavy Flavour Physics impact on these questions? Does it offer novel windows onto New Physics beyond the Standard Model in general and onto new symmetries, such as Supersymmetry in particular? These questions constitute the central theme of this book. The material treated in this publication may serve as reference for the segment of the high-energy community actively engaged in heavy-quark physics.
Logic Of Nature, Complexity And New Physics, The: From Quark-gluon Plasma To Superstrings, Quantum Gravity And Beyond - Proceedings Of The International School Of Subnuclear Physics
Author: Antonino Zichichi
language: en
Publisher: World Scientific
Release Date: 2008-07-04
From August 29 to September 7, 2006, a large group of distinguished lecturers and young physicists coming from various countries around the world met in Erice, Italy, at the Ettore Majorana Foundation and Centre for Scientific Culture (EMFCSC) for the 44th course of the International School of Subnuclear Physics: “The Logic of Nature, Complexity and New Physics: From Quark-Gluon Plasma to Superstrings, Quantum Gravity and Beyond”.This book is a collection of lectures given during the course, covering the most recent advances in theoretical physics and the latest results from current experimental facilities. Following one of the aims of the School, which is to encourage and promote young physicists to achieve recognition at an international level, the students who have distinguished themselves for their excellence in research have been given the opportunity to publish their presentations in this volume.