1 - Introduction and overview

Summary

Elementary particle physics

Elementary particle physics is the study of the fundamental constituents of matter and the forces between them. It is also called High Energy Physics (HEP) because in order to study fundamental particles with smaller and smaller sizes, shorter and shorter wavelength probes are required which correspond to higher and higher energy.

The field of high energy physics has proceeded for the past ˜60 years in a typical sequence: a new accelerator opened up a new range of available energy (or type of accelerated particle, e.g. colliding beams of positrons and electrons), and coupled with new detector technology – which enabled improved or previously impossible measurements to be made – rapidly yielded discoveries soon after it started up. The hadron accelerators which have had the most influential impact on the modern high energy particle and heavy ion physics discussed in this book are shown in Figure 1.1. The upper branch shows four major generations of p–p(p) colliders starting from the CERN Intersecting Storage Rings (ISR), the first hadron collider, while the lower branch depicts the major heavy ion facilities in the USA and Europe. The AGS at Brookhaven National Laboratory (BNL) ran for p–p physics from 1960–2002 and is now the injector to RHIC. The fixed target p–p programs of Fermilab (1972–) and the CERN-SPS (1976–) are also not shown.