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Run II begins at the Tevatron

29 April 2001

Back in operation for particle physics for the first time since
1996, Fermilab’s superconducting Tevatron proton-antiproton collider is set to write a major new chapter of science
history. What is officially called Run II of the collider will continue, with interruptions for maintenance and upgrades,
until 2007, by which time CERN’s LHC collider will have made its debut.

For Run II the Tevatron’s beams
have been boosted from 900 to 980 GeV (collision energy 1960 GeV), the highest-energy particle accelerator now
operating in the world. As well as providing extra energy, the Run II Tevatron is fed by Fermilab’s 150 GeV Main
Injector synchrotron, which was commissioned in 1999 and replaced Fermilab’s original Main Ring.

The
Tevatron and the Main Ring originally shared the same tunnel, which had a four mile circumference. However, the
Main Ring, which has now been removed, became a bottleneck in Fermilab’s particle supply. With the new Main
Injector, proton-antiproton collision rates (luminosity) should be boosted twentyfold.

Monitoring these
collisions are the Tevatron’s two major collider detectors, CDF and D0. Each have completed five-year upgrades
costing USD 100 million to take advantage of the Tevatron’s enhanced capabilities.

Late last year,
experiments at CERN’s Large Electron-Positron (LEP) collider detected hints of the long-awaited Higgs particle, the
source of mass in the unified theory of weak and electromagnetic interactions. However, LEP was shut down before
scientists could either confirm or rule out a Higgs sighting (see Season of Higgs and melodrama;March 2001). For the
next few years, the Tevatron has no competitor in the Higgs race.

Run II also has the potential for revealing
much more, including evidence for supersymmetry – a possible doubling of the known number of fundamental
particles, new insights into the CP-violation mechanism responsible for asymmetry between matter and antimatter,
and a better understanding of the sixth “top” quark, discovered at Fermilab in 1995 during Tevatron Collider Run
I.

The Tevatron saw its first proton-antiproton collisions in 1985, and for its first phase of operations (pre-Run
I, until 1989) ran with a single detector, CDF. For Run I (1992-1996), CDF was joined by the D0 detector.

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