tailieunhanh - Elementary Particles In Physics

Particle physics today is one of the leading edge of modern physics. This document provides the reader with information about the world of particle physics has been discovered. From the classification of elementary particles to the interaction between them, from the electromagnetic interaction to strong interaction and weak interaction. Hopefully this document will meet the needs of you spend a lot of interest for fundamental particles. | ELEMENTARY PARTICLES IN PHYSICS 1 Elementary Particles in Physics S. Gasiorowicz and P. Langacker Elementary-particle physics deals with the fundamental constituents of matter and their interactions. In the past several decades an enormous amount of experimental information has been accumulated and many patterns and systematic features have been observed. Highly successful mathematical theories of the electromagnetic weak and strong interactions have been devised and tested. These theories which are collectively known as the standard model are almost certainly the correct description of Nature to first approximation down to a distance scale 1 1000th the size of the atomic nucleus. There are also speculative but encouraging developments in the attempt to unify these interactions into a simple underlying framework and even to incorporate quantum gravity in a parameter-free theory of everything. In this article we shall attempt to highlight the ways in which information has been organized and to sketch the outlines of the standard model and its possible extensions. Classification of Particles The particles that have been identified in high-energy experiments fall into distinct classes. There are the leptons see Electron Leptons Neutrino Muonium all of which have spin 1. They may be charged or neutral. The charged leptons have electromagnetic as well as weak interactions the neutral ones only interact weakly. There are three well-defined lepton pairs the electron e- and the electron neutrino ve the muon p- and the muon neutrino vM and the much heavier charged lepton the tau t and its tau neutrino vT . These particles all have antiparticles in accordance with the predictions of relativistic quantum mechanics see CPT Theorem . There appear to exist approximate lepton-type conservation laws the number of e- plus the number of ve minus the number of the corresponding antiparticles e and ve is conserved in weak reactions and similarly for the muon and tau-type leptons. .