Overview More explanations Cleo

Beginners Guide to HEP

What is High Energy Physics?
`High Energy Physics' (HEP) or `Particle Physics' searches for the fundamental particles and forces which build the world around us.

Like all matter is made from atoms, all atoms are made from even smaller particles. Physicist discovered that similiar to the `Periodic System of Atoms', there is a list of subatomic particles.
We create those particles (which are not a normal part of matter we encounter everyday) by using the famous `Einstein Law' that relates energy and matter: E = m c**2.
Compared to natural processes on earth, like the creation of a lightning or the energy released in a nuclear decay, the energy per particle is many magnitudes higher. That's why this field is called `High Energy Physics'.

Particles and Fields
Besides the basic particles (called `fermions' after E. Fermi), there are also the basic forces between them. We now know four different forces (sorted by their relative strengths): the Gravitational Force (e.g. between Sun and Earth)
the Electromagnetic Force (e.g. between magnets)
the Weak Force (e.g. in nuclear decays)
the Strong Force (e.g. binding the nucleus of the atom)
One surprising result of the last 50 years of research was, that you can describe those forces with the exchange of particles. For example the photon is created in electromagnetic processes. You also know it as normal light.
Those particles (called `bosons', honouring S.N. Bose) can also be produced in current experiments. Up to now gravitation can not be completely described in this way, but the theorists are working hard to achieve this goal.

The Particle Zoo
A basic experimental fact in HEP is, that every particle has a `mirror counterpart', called the anti-particle. (This was actually a prediction by P.A.M. Dirac, who tried to discribe the behaviour of fundamental particles)
In some rare cases the particle is its own anti-particle. The difference between particle and anti-particle is a sign change in all `number-like' properties, like the charge. All others, like the mass, are unchanged. For instance the anti-particle of the electron is called positron, which has the same mass but the opposite charge. These two particles are used at CESR, at which CLEO is located, to create other particles with higher mass. In a reaction of a particle and anti-particle both are annihilated and all energy is available to create new particles. (Or to drive the future WARP engine of a star ship)

Experiments with Fundamental Particles
Since the fundamental particles are even smaller in size than atoms, you can't see them directly, even with this very good microscope. Physicists have therefore built very complicated detectors to find those particles and measure their properties. Some of them are taller than a three story building!
They all rely on the fact, that after their production those particles will interact with parts of the detector and leave typical `traces'. In some special experiments you even can find `missing particles' very accurately, so that very elusive particles, like the neutrino, can be found.

The CLEO detector
The OSU CLEO group is doing experimental research with the CLEO detector. You can find a more detailed description of this detector on this WEB server.

How do we do HEP with CLEO?
If you want to know, how we find particles at CLEO, follow the pictures showing a reaction inside of the detector
Do it Yourself!
After reading this, you should try to find them for yourself, with this
interactive form.

Take a look into HEPnet
There is a HEP information center, which beams you directly into the HEP community!
Try High Energy Physics Information Center

Access to this page: 198 times since 2-Jan-96 CronCount
Overview More explanations Cleo
Updated: 27. July 1995
Author: Andreas H. Wolf (ahw@mps.ohio-state.edu)