Scientists complete the top quark puzzle
Scientists on the CDF and DZero experiments at the U.S. Department of Energy’s Fermi National Accelerator Laboratory have announced that they have found the final predicted way of creating a top quark, completing a picture of this particle nearly 20 years in the making.
The two collaborations jointly announced on Friday, Feb. 21, that they had observed one of the rarest methods of producing the elementary particle – creating a single top quark through the weak nuclear force, in what is called the “s-channel.” For this analysis, scientists from the CDF and DZero collaborations sifted through data from more than 500 trillion proton-antiproton collisions produced by the Tevatron from 2001 to 2011. They identified about 40 particle collisions in which the weak nuclear force produced single top quarks in conjunction with single bottom quarks.
Top quarks are the heaviest and among the most puzzling elementary particles. They weigh even more than the Higgs boson – as much as an atom of gold – and only two machines have ever produced them: Fermilab’s Tevatron and the Large Hadron Collider at CERN. There are several ways to produce them, as predicted by the theoretical framework known as the Standard Model, and the most common one was the first one discovered: a collision in which the strong nuclear force creates a pair consisting of a top quark and its antimatter cousin, the anti-top quark.
Collisions that produce a single top quark through the weak nuclear force are rarer, and the process scientists on the Tevatron experiments have just announced is the most challenging of these to detect. This method of producing single top quarks is among the rarest interactions allowed by the laws of physics. The detection of this process was one of the ultimate goals of the Tevatron, which for 25 years was the most powerful particle collider in the world.
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http://www.fnal.gov/pub/presspass/press_releases/2014/Top-Quark-Puzzle-20140224.html
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Some pics.
The Tevatron.
Night, with awesome admin building.
Inside the accelerator tunnel ring.
Ground floor of the admin building.
The Cockroft Walton injector. (Yup! It's like SciFi. And yup! It's big.)
I worked for a semester at the sister lab, Argonne National Laboratory and was lucky to get a VIP tour of Fermilab while they were working on the Tevatron. We got into areas where the public tours never saw. Pretty damned amazing.
and great news!
