Transcript ATLAS Experiment at CERN Why Build ATLAS?    Before the LHC there was LEP (large electron positron collider) the experiments at LEP had.

ATLAS Experiment at CERN
Why Build ATLAS?
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Before the LHC there was LEP (large electron positron collider)
the experiments at LEP had observed the W and Z boson which
carry the weak force. At the upper end of the LEP energies it was
hypothesised that the Higgs Boson would be observed.
The Higgs boson is only one particle left in the standard model
that has yet to be observed.
It is unknown why fundamental particles have such varying masses
and it is believed that the discovery of the higgs boson could help
to answer some of these questions.
Although the higgs boson was the main motivation for building ATLAS
it is also hoped that it will answer other questions left open by the
standard model such as:
1-Why are there three types of quarks and leptons of each charge?
2-Are there more types of particles and forces to be discovered?
3-Are the quarks and leptons really fundamental, or do they, too,
have substructure?
4-What particles form the dark matter in the universe?
5-How can the gravitational interactions be included in the standard
model?
Why can ATLAS answer these
questions?
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The LHC will provide colliding beams of much greater energy than
available at LEP. The maximum energy of the protons in the beam will be
7TeV.
From Einstein’s famous equation
it is known that mass and energy are equivalent.
The higher energy beam means that in a collision a more massive particle
can be produced. This will be needed if the Higgs boson is to be observed.
Higher energy beams may also answer some of the questions left from the
standard model.
The ATLAS Detector
A diagram of the ATLAS detector which is the size of a five story
building
The Higgs Boson
The higgs boson is the last of the particles predicted by the
standard model yet to be detected directly.
 The Higgs is believed to exist in a field which is present in all of
space. An analogy to both of these is given below.
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To understand the Higgs mechanism, imagine that
a room full of physicists chattering quietly is like
space filled with the Higgs field ...
... a well-known scientist walks in, creating a
disturbance as he moves across the room and
attracting a cluster of admirers with each step ...
... this increases his resistance to movement, in
other words, he acquires mass, just like a particle
moving through the Higgs field
... if a rumor crosses the room, ...
... it creates the same kind of
clustering, but this time among the
scientists themselves. In this
analogy, these clusters are the
Higgs particles.
What if the Higgs boson is not Found?
If the Higgs is not found then there are plenty of other things that
scientists at ATLAS can search for.
 GUTS- Grand Unified Theory, where all the forces will act
together as one -already started with Maxwell’s theory of
electromagnetism.
 -electroweak theory by Glashow, Salam, and Wienberg.
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Other possible searches include looking for supersymmetry and dark
matter.