Particle Physics

Brian R. Martin, Graham Shaw

• Publisher: Wiley
• Year: 2016
• ISBN:
  9781118912218
• Edition: 4
• Topic: Ciencias físicas
• Subtopic: Física nuclear

An accessible and carefully structured introduction to Particle Physics, including important coverage of the Higgs Boson and recent progress in neutrino physics.

• Fourth edition of this successful title in the Manchester Physics series
• Includes information on recent key discoveries including: An account of the discovery of exotic hadrons, byond the simple quark model;Expanded treatments of neutrino physics and CP violationin B -decays;An updated account of 'physics beyond thestandard model', including the interaction of particle physics withcosmology
• Additional problems in allchapters, with solutions to selected problems available on the book's website
• Advanced material appears in optional starred sections

1
Some basic concepts

1.1 Introduction

Particle physics is the study of the fundamental constituents of matter and their interactions. However, which particles are regarded as fundamental has changed with time as physicists' knowledge has improved. Modern theory – called the standard model – attempts to explain all the phenomena of particle physics in terms of the properties and interactions of a small number of particles of four distinct types: two spin-1/2 families of fermions called leptons and quarks; one family of spin-1 bosons – called gauge bosons – which act as ‘force carriers’ in the theory; and a spin-0 particle, called the Higgs boson, which explains the origin of mass within the theory, since without it, leptons, quarks and gauge bosons would all be massless. All the particles of the standard model are assumed to be elementary: that is they are treated as point particles, without internal structure or excited states.

The most familiar example of a lepton is the electron e⁻ (the superscript denotes the electric charge), which is bound in atoms by the electromagnetic interaction, one of the four fundamental forces of nature. A second well-known lepton is the electron neutrino ν_e, which is a light, neutral particle observed in the decay products of some unstable nuclei (the so-called β decays). The force responsible for the β decay of nuclei is called the weak interaction.

Another class of particles called hadrons is also observed in nature. Familiar examples are the neutron n and proton p (collectively called nucleons) and the three pions (π⁺, π⁻, π⁰), where the superscripts again denote the electric charges. These are not elementary particles, but are made of quarks bound together by a third force of nature, the strong interaction. The theory is unusual in that the quarks themselves are not directly observable, only their bound states. Nevertheless, we shall see in later chapters that there is overwhelming evidence for the existence of quarks and we shall discuss the reason why they are unobservable as free particles. The strong interaction between quarks gives rise to the observed strong interaction between hadrons, such as the nuclear force that binds nucleons in nuclei. There is an analogy here with the fundamental electromagnetic interaction between el...