The Standard Model
The Standard Model is the name given to the current theory of fundamental particles and how they interact. This theory includes:
- Strong interactions due to the color charges of quarks and gluons.
- A combined theory of weak and electromagnetic interaction, known as electroweak theory, that introduces W and Z bosons as the carrier particles of weak processes, and photons as mediators to electromagnetic interactions.
The theory does not include the effects of gravitational interactions. These effects are tiny under high-energy Physics situations, and can be neglected in describing the experiments. Eventually, we seek a theory that also includes a correct quantum version of gravitational interactions, but this is not yet achieved.
The Standard Model was the triumph of particle physics of the 1970's . It incorporated all that was known at that time and has since then successfully predicted the outcome of a large variety of experiments. Today, the Standard Model is a well established theory applicable over a wide range of conditions.
Higgs Physics
One part of the Standard Model is not yet well established. We do not know what causes the fundamental particles to have masses. The simplest idea is called the Higgs mechanism. This mechanism involves one additional particle, called the Higgs boson, and one additional force type, mediated by exchanges of this boson.
The Higgs particle has not yet been observed. Today we can only say that if it exists, it must have a mass greater than about 80GeV/c2. Searches for a more massive the Higgs boson are beyond the scope of the present facilities at SLAC or elsewhere. Future facilities, such as the Large Hadron Collider at CERN, or upgrades of present facilities to higher energies are intended to search for the Higgs particle and distinguish between competing concepts.
Thus, this one aspect of the Standard Model does not yet have the status of "theory" but still remains in the realm of hypothesis or model.
