High Energy Particle Physics - the Study of Fundamental Particles and Forces

The subject of particle physics concerns itself with the basic constituents of matter at the most fundamental nature - the subatomic particles from which all matter in the known universe is made.

In the first part of the twentieth century it was believed that all matter was made from atoms composed of just three basic particles - positively charged protons and electrically neutral neutrons forming a central nucleus, with negatively charged electrons circulating in orbits around it.

However, studies on these seemingly fundamental particles in the mid part of the twentieth century soon revealed that the protons and neutrons are in themselves composed of even smaller particles - the so called quarks (which are also present in more exotic kinds of particles found in the cosmic radiation originating from outside our own galaxy) and exchange particles called gluons which hold them together.

Protons and neutrons are made from different combinations of just two types or "flavours" of quark (called "up" and "down" quarks) but four other flavours of quark (called "strange", "charm", "bottom" and "top") have also been identified in particles found in cosmic rays and accelerator experiments (see below), making six in all. Together with six types of lepton (the electron, the electron-neutrino, the muon, the muon-neutrino, the tau, and the tau-neutrino), the gluons and the intermediate vector bosons (special force carrying entities which allow the quarks and leptons to interact) these particles are currently believed to be the fundamental building blocks from which all matter in the universe is made.

The subject of particle physics deals with the detection and measurement of the properties and behavior of these fundamental particles, along with the four apparantly distinct forces by which they are known to interact. These four forces are categorised as the electromagnetic, strong nuclear and weak nuclear forces, as well as gravity. The weak nuclear and electromagnetic forces have already been shown to be two different aspects of a single underlying "electroweak" force, and it is believed that this will be combined with the strong nuclear force in a "Grand Unified Theory" (or GUT) at some point in the future - followed by the addition of gravity within a mooted "Theory of Everything" (or ToE). The eventual demonstration that all four forces are different manifestations of one single underlying force is thus the ultimate aim and "Holy Grail" of particle physics.

[N.B. It is a very strange world indeed, as subatomic particles do not behave according to the "intuitive" and deterministic laws of classical physics (which account for phenomenon as seen at the macroscopic level in our everyday lives), but rather they obey the laws of quantum mechanics (a theory which was developed to account for the very different way that very small objects such as fundamental particles are believed to behave).]

To study these basic particles and forces huge particle accelerators (machines capable of accelerating subatomic particles and colliding them at very high energies) are required. Because of the scale of these particle accelerators (which are often tens of kilometres long) they are often built in underground tunnels at international laboratories such as CERN near Geneva in Switzerland, Fermilab near Chicago in the USA, DESY in Hamburg in Germany, SLAC in California, and JINR in Russia and KEK in Japan, as well as others throughout the world. [N.B. Please click here for more information about particle physics laboratories worldwide.]

Typical experiments in the subject often involve hundreds or even thousands of physicists, usually working within multinational research teams at the above laboratories. In addition, engineers and technicians from various different fields (including engineering, electronics, computing etc) are also needed to support the experimentalists, who often work round the clock on shifts while their experiments collect valuable data. Processing the vast amount of information which is collected is a mammoth task which often pushes computing technology to its limits, and particle physics has often been seen as a driving force towards the development of better and faster computers and computing as well as communications technology too. [N.B. The World Wide Web for instance was developed at CERN; you can find out more about this in the context of the history of the Internet by clicking here.]

Besides using accelerators, particle physics can also be studied by observing cosmic radiation, which includes high energy particles and gamma rays which rain down on our planet from outer space. Such experiments are often conducted at high altitudes or very deep underground at installations such as the Gran Sasso laboratory in Italy and the Boulby Mine at Boulby on the Yorkshire Coast in the UK.

Although often thought to be quite esoteric, the pursuit of knowledge in the field of high energy physics has led to many practical "spin off" developments in areas as diverse as cyrogenics, medicine, electronic sensing, computer technology and telecommunications. Probably one of the most significant of these developments in recent years has been that of the World Wide Web - the now globally accepted format for presenting information across the Internet which was invented at CERN and which you will probably be using to read this page(!)

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