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Protons meet antiprotons at 1,600 GeV.

Protons meet antiprorons at 1,600 GeV

X marks the spot (between top and bottom octants) where a proton with 800 billion electron-volts (800 GeV) energy collided head-on with an antiproton of equal energy in the Tevaltron (SN: 9/28/85, p. 202) at the Fermi National Accelerator Laboratory in Batavia, Ill. This is one of the first collisions at that energy, the highest in the world and nearly three times that of the nearest competitor.

The very high multiplicity of things produced in the collision is immediately apparent on the plot. Each line of dots represents the track of some kind of particle made in the collision. As the detector is three-dimensional, the tracks are color-coded according to the octant of the third dimension in which they appear. The circle at left divides the third dimension into octants and indicates the color assigned to each.

This ia a test run, and its importance, according to Roy Schwitters of Fermilab, is to show that "the apparatus really works." Right now the apparatus is down while the detector is being completed and adjustments are made to permit actual ecperimental runs, which Schwitters expects to start in November. When the Tevatron is working at its design capacity, about 50,000 of these collisions will occur every second. At that time, ironically, a trigger on the detector will throw out the ones that look like this, which is quite ordinary. The physicists are interested in rare particles like Ws and Zs that appear only once in many thousands of collisions. In three months of running they anticipate recording about 100 Ws.
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Author:Thomsen, Dietrich E.
Publication:Science News
Date:Mar 22, 1986
Words:268
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