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Fermilab is home to the
Tevatron, the world's highest-energy
particle accelerator. Four miles in circumference, the Tevatron is housed in a tunnel about 30 feet below the big ring
you see at right in the
aerial view of the laboratory. A series of
accelerators continuously add energy to
subatomic particles until they are
racing around the Tevatron at 99.999 percent of the
speed of light in a vacuum.
Discoveries are made by
smashing the speeding subatomic particles together to see what comes flying out.
In the Tevatron, two kinds of particles -
protons and antiprotons - are sent around the ring in bunches, or "beams", in opposite directions.
At a million times a second, the
proton-antiproton collisions reach an energy level of 1.96
trillion electron volts (TeV) and
are directed to the interaction points at the centers of the
D0
and
CDF detectors.
The luminosity of an accelerator is a measure of the number of particle collisions that occur each second. The energy of Tevatron collisions
cannot be significantly raised therefore increasing the number and rate of collisions is the only
path to discovery. To increase the number of collisions,
accelerator experts try to maximize the peak luminosity, or initial number of protons and antiprotons, of each
store to the Tevatron.
A store produces about 10 to 20 hours of collisions. Raising the peak luminosity for each
store maximizes the integrated luminosity,
the cumulative total of particle collisions over the entire collider run. The higher the integrated luminosity, usually measured in
inverse picobarns (pb-1), the greater the possibility of discovery.
The Tevatron collider physics program is comprised of two stages: Run I and Run II. From 1992
to 1996, the Run I collider program, operating at an energy level of 1.8 TeV, delivered to each experiment an
integrated luminosity in excess of 160 pb-1,
which was sufficient to discover the top quark.
To continue the discovery of new particles, a series of improvements were made to the Tevatron over a five-year hiatus to provide
a total energy of 1.96 TeV at the collision points, a 10 percent increase over the energy of Run I, and to deliver more than a
20-fold increase in the number of particle collisions observed and recorded at the particle detectors.
In addition, the detectors completed upgrades to take advantage of the Tevatron's enhanced capabilities.
The Tevatron Run II collider program began
March 1st 2001, and is scheduled to run through mid-2009.
The DZero Experiment utilized the first year of
collisions to commission the detector, trigger and electronics elements needed to perform physics measurements.
The last major element to be completed - the central tracker - which is crucial for particle position and charge determination,
was fully instrumented in April 2002, marking the beginning of the
DZero Run II Physics Program.
By May 2003, the
Run II integrated luminosity recorded by the D0 detector had surpassed the
total luminosity recorded in Run I.
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