Partikelfysik og højenergifysik

This book describes the first application at CMS of deep learning algorithms trained directly on low-level, ¿raw¿ detector data, or so-called end-to-end physics reconstruction. Growing interest in searches for exotic new physics in the CMS collaboration at the Large Hadron Collider at CERN has highlighted the need for a new generation of particle reconstruction algorithms. For many exotic physics searches, sensitivity is constrained not by the ability to extract information from particle-level data but by inefficiencies in the reconstruction of the particle-level quantities themselves. The technique achieves a breakthrough in the reconstruction of highly merged photon pairs that are completely unresolved in the CMS detector. This newfound ability is used to perform the first direct search for exotic Higgs boson decays to a pair of hypothetical light scalar particles H¿aa, each subsequently decaying to a pair of highly merged photons äyy, an analysis once thought impossible to perform. The book concludes with an outlook on potential new exotic searches made accessible by this new reconstruction paradigm.

This book is about the energy loss and the coherent radiation emitted by a relativistic charge in matter. These phenomena ¿ locally deposited energy, Cherenkov radiation and transition radiation ¿ are the basis of any charged particle detector able to discriminate charges by their velocity. This book describes these phenomena and how they are related. The fundamental field equations and first principles are used to derive the spectrum of energy-loss signals and thence the velocity resolution that can be achieved. Two specific applications are then followed: the first shows that this resolution has been achieved in practice with a multi-particle detector in the course of an experiment at CERN, and the second shows how, by including scattering, the technique of ionisation cooling of accelerator beams may be reliably simulated. The book is based on a series of lectures given at the University of Oxford to graduate students in experimental particle physics. Some knowledge of mathematical physics at an undergraduate level is assumed, specifically Maxwell¿s equations and classical optics.

This book begins with an overview of the RF control concepts and strategies. It then introduces RF system models for optimizing the system parameters to satisfy beam requirements and for controller design. In addition to systematically discussing the RF field control algorithms, it presents typical architecture and algorithms for RF signal detection and actuation. Further, the book addresses the analysis of the noise and nonlinearity in LLRF systems to provide a better understanding of the performance of the RF control system and to specify the performance requirements for different parts of the RF system. Today, accelerators require increased RF stability and more complex operation scenarios, such as providing beam for different beam lines with various parameters, and as a result LLRF systems are becoming more critical and complex. This means that LLRF system developers need have extensive knowledge of the entire accelerator complex and a wide range of other areas, including RF and digital signal processing, noise analysis, accelerator physics and systems engineering.Providing a comprehensive introduction to the basic theories, algorithms and technologies, this book enables LLRF system developers to systematically gain the knowledge required to specify, design and implement LLRF systems and integrate them with beam acceleration. It is intended for graduate students, professional engineers and researchers in accelerator physics.

This thesis presents a search for long-lived particles decaying into displaced electrons and/or muons with large impact parameters. This signature provides unique sensitivity to the production of theoretical lepton-partners, sleptons. These particles are a feature of supersymmetric theories, which seek to address unanswered questions in nature. The signature searched for in this thesis is difficult to identify, and in fact, this is the first time it has been probed at the Large Hadron Collider (LHC). It covers a long-standing gap in coverage of possible new physics signatures. This thesis describes the special reconstruction and identification algorithms used to select leptons with large impact parameters and the details of the background estimation. The results are consistent with background, so limits on slepton masses and lifetimes in this model are calculated at 95% CL, drastically improving on the previous best limits from the Large Electron Positron Collider (LEP).

This book presents a review of various issues related to Lorentz symmetry breaking. Explicitly, we consider (i) motivations for introducing Lorentz symmetry breaking, (ii) classical aspects of Lorentz-breaking field theory models including typical forms of Lorentz-breaking additive terms, wave propagation in Lorentz-breaking theories, and mechanisms for breaking the Lorentz symmetry; (iii) quantum corrections in Lorentz-breaking theories, especially the possibilities for perturbation generating the most interesting Lorentz-breaking terms; (iv) correspondence between non-commutative field theories and Lorentz symmetry breaking; (v) supersymmetric Lorentz-breaking theories; and (vi) Lorentz symmetry breaking in a curved space-time. We close the book with the review of experimental studies of Lorentz symmetry breaking.The importance and relevance of these topics are explained, first, by studies of limits of applicability of the Lorentz symmetry, second, by searches of the possible extensions of the standard model, including the Lorentz-breaking ones, and need to study their properties, third, by the relation between Lorentz symmetry breaking with string theory, fourth, by the problem of formulating a consistent quantum gravity theory, so that various modified gravity models are to be examined.

This book provides a modern perspective on the analytic structure of scattering amplitudes in quantum field theory, with the goal of understanding and exploiting consequences of unitarity, causality, and locality. It focuses on the question: Can the S-matrix be complexified in a way consistent with causality? The affirmative answer has been well understood since the 1960s, in the case of 2¿2 scattering of the lightest particle in theories with a mass gap at low momentum transfer, where the S-matrix is analytic everywhere except at normal-threshold branch cuts. We ask whether an analogous picture extends to realistic theories, such as the Standard Model, that include massless fields, UV/IR divergences, and unstable particles. Especially in the presence of light states running in the loops, the traditional i¿ prescription for approaching physical regions might break down, because causality requirements for the individual Feynman diagrams can be mutually incompatible. We demonstrate that such analyticity problems are not in contradiction with unitarity. Instead, they should be thought of as finite-width effects that disappear in the idealized 2¿2 scattering amplitudes with no unstable particles, but might persist at higher multiplicity. To fix these issues, we propose an i¿-like prescription for deforming branch cuts in the space of Mandelstam invariants without modifying the analytic properties of the physical amplitude. This procedure results in a complex strip around the real part of the kinematic space, where the S-matrix remains causal. We illustrate all the points on explicit examples, both symbolically and numerically, in addition to giving a pedagogical introduction to the analytic properties of the perturbative S-matrix from a modern point of view. To help with the investigation of related questions, we introduce a number of tools, including holomorphic cutting rules, new approaches to dispersion relations, as well as formulae for local behavior of Feynmanintegrals near branch points. This book is well suited for anyone with knowledge of quantum field theory at a graduate level who wants to become familiar with the complex-analytic structure of Feynman integrals.

This text provides coverage of laser safety fundamentals and a broad range of real world laser safety topics. As a highly useful research and reference book it addresses many unique laser safety challenges.

This book offers an original view of the color confinement/deconfinement transition that occurs in non-abelian gauge theories at high temperature and/or densities. It is grounded on the fact that the standard Faddeev-Popov gauge-fixing procedure in the Landau gauge is incomplete. The proper analysis of the low energy properties of non-abelian theories in this gauge requires, therefore, the extension of the gauge-fixing procedure, beyond the Faddeev-Popov recipe.The author reviews various applications of one such extension, based on the Curci-Ferrari model, with a special focus on the confinement/deconfinement transition, first in the case of pure Yang-Mills theory, and then, in a formal regime of Quantum Chromodynamics where all quarks are considered heavy. He shows that most qualitative aspects and also many quantitative features of the deconfinement transition can be accounted for within the model, with only one additional parameter. Moreover, these features emerge in a systematic and controlled perturbative expansion, as opposed to what would happen in a perturbative expansion within the Faddeev-Popov model.The book is also intended as a thorough and pedagogical introduction to background field gauge techniques at finite temperature and/or density. In particular, it offers a new and promising view on the way these techniques might be applied at finite temperature. The material aims at graduate students or researchers who wish to deepen their understanding of the confinement/deconfinement transition from an analytical perspective. Basic knowledge of gauge theories at finite temperature is required, although the text is designed in a self-contained manner, with most concepts and tools introduced when needed. At the end of each chapter, a series of exercises is proposed to master the subject.

This book introduces the scattering theory of nonrelativistic systems, a standard tool for interpreting collision experiments with quantum particles at energies not too high. The goal is to explore the interaction between particles and their properties. The authors cover the basics of the theory through a detailed discussion of elastic scattering using the stationary Schrodinger equation and the Lippmann-Schwinger equation. These remarks are supplemented by a consideration of the time-dependent formulation of scattering theory. Selection rules for effective cross sections due to symmetries conditioned by the structure of the interparticle forces and the scattering of spin-polarized particles are discussed. The foundations for the treatment of inelastic processes are laid and explained by application to three-body and nucleotransfer processes.In all chapters, the more technical, mathematical aspect and the more physics-oriented explanations are separated as far as possible. The explanations are well comprehensible and suitable to introduce the reader to the physics of impact processes.This book is a translation of the original German 1st edition Streutheorie in der nichtrelativistischen Quantenmechanik by Reiner M. Dreizler, Tom Kirchner & Cora S. Ludde, published by Springer-Verlag GmbH Germany, part of Springer Nature in 2018. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). The present version has been revised extensively with respect to technical and linguistic aspects by the authors. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors.

"This modern text describes the remarkable developments in quantum condensed matter physics following the experimental discoveries of quantum Hall effects and high temperature superconductivity in the 1980s. After a review of the phases of matter amenable to an independent particle description, entangled phases of matter are described in an accessible and unified manner. The concepts of fractionalization and emergent gauge fields are introduced using the simplest resonating valence bond insulator with an energy gap, the Z2 spin liquid. Concepts in band topology and the parton method are then combined to obtain a large variety of experimentally relevant gapped states. Correlated metallic states are described, beginning with a discussion of the Kondo effect on magnetic impurities in metals. Metals without quasiparticle excitations are introduced using the Sachdev-Ye-Kitaev model, followed by a discussion of critical Fermi surfaces and strange metals. Numerous end-of-chapter problems expand readers' comprehension and reinforce key concepts"--

This is a problem-oriented introduction to the main ideas, methods, and problems needed to form a basic understanding of the theory of strong interactions.

The birth of the Universe, and its subsequent evolution, is an exciting blend of Cosmology, Particle Physics and Thermodynamics. This book, with its synoptic approach, provides an accessible introduction to these fascinating topics. It begins in Part I with an overview of cosmology and is followed by a discussion on the present understanding about the birth of the universe, detailing the Planck Era, Inflation, and the Big Bang. It speculates the possibility of multiple universes. Before moving on to explore the essentials of the Standard Model of Particle Physics in Part II, with particular stress on the electroweak force, the first example of acquisition of mass by gauge bosons via the Higgs mechanism. The book finishes in Part III with the thermal history of the Universe. This will also lead to understanding baryonic matter and baryogenesis as well as nucleosynthesisThis book is suitable for those taking courses on particle physics, general relativity, and cosmology. Readers mathematically inclined who wish to enhance their basic knowledge about the early Universe, will also find this book suitable to move up to the next level.Features:Authored by experienced lecturers in Particle Physics, Quantum Field Theory, Nuclear Physics, and General RelativityProvides an accessible introduction to Particle Physics and Cosmology

With his extraordinary gift for making the complicated comprehensible, Anil Ananthaswamy travels around the world and through history, down to the smallest scales of physical reality we have yet fathomed for the answers.

In the summer of 1964, a reclusive young professor at the University of Edinburgh wrote two scientific papers which have come to change our understanding of the most fundamental building blocks of matter and the nature of the universe. Peter Higgs posited the existence an almost infinitely tiny particle - today known as the Higgs boson - which is the key to understanding why particles have mass, and but for which atoms and molecules could not exist.For nearly 50 years afterwards, some of the largest projects in experimental physics sought to demonstrate the physical existence of the boson which Higgs had proposed. Sensationally, confirmation came in July 2012 at the Large Hadron Collider at CERN in Geneva. The following year Higgs was awarded the Nobel Prize for Physics. One of the least-known giants of science, he is the only person in history to have had a single particle named for them.This revelatory book is 'not so much a biography of the man but of the boson named after him'. It brilliantly traces the course of much of twentieth-century physics from the inception of quantum field theory to the completion of the 'standard model' of particles and forces, and the pivotal role of Higgs's idea in this evolution. It also investigates the contested history of Higgs's responsibility for the breakthrough when there were others close by, and explains why the boson is named for him alone. Competition between institutions and states, Close shows, then played as much of a role in creating Higgs's fame as his work itself. Drawing on conversations with Higgs over a decade (a figure generally as elusive as his particle) this is a superb study of a scientist and his era - and of how scientific knowledge advances.