The Standard Model is the name given to the current theory of
fundamental
particles and how they
interact.
This theory includes:
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.
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.
For more see Creative Particles of Higgs;
Farsi translation,
English translation
