particle physics?
 |
guided tour
   |
--->
--> 
->  |
| 1a.
What is
particle physics?
|
|
| Particle physics, also called "high energy physics,"
is the study of the elementary particles and their interactions.
An elementary particle is one that is not made up of other, even smaller,
particles. We know that matter as we see it here on earth is made
up of tiny particles called atoms, and that each atom is composed of some
combination of three particles, protons, neutrons, and electrons.
The proton has positive electric charge, the neutron has zero charge, and
the electron has a negative charge that is equal in magnitude to that of
the proton. We now believe that the proton and neutron are made up
of even smaller particles, called quarks.
Interactions, or forces, between particles are responsible for making things happen such as holding matter together. The two most familiar forces are gravitation and electromagnetism. Let's take the electromagnetic force to illustrate some general features. The force is easily observed if you put electric charge on objects (just rub a piece of acrylic plastic with wool) and feel the invisible attraction or repulsion. It's a force that exists between any two objects with electric charge. A different force might not be affected by the electric charge of particles, but could have its own version of charge, a property carried by some particles, such that the force exists between two particles carrying that form of charge. In addition to gravitation and electromagnetism, particles are known to be influenced by two other forces, known as the strong and weak forces. There are a few confirmed properties of matter and interactions that derive from the concepts of modern physics and that you will need to know to understand a description of particle physics and CP violation in particular. One is that matter can be turned into energy and vice versa, a fact embodied in the famous equation, E=mc2. Another is that it's possible for elementary particles to turn into other elementary particles, given the right conditions. Among other things, this allows for the decay of some elementary particles, which occurs through the weak interaction. Another is the concept of antimatter -- that every elementary particle has an antimatter partner, that if the two come together they can annihilate and leave pure energy in their place. |