An Enormous Search For A Tiny Particle: Finding the top quark
900 Physicists On The Hunt For The Elusive Top Quark
Trillions of times smaller than a grain of sand and smaller than an atomic proton or neutron, quarks are among the smallest particles in the universe. They are essentially building blocks for everything in our universe.
After physicists working at the Fermi National Accelerator Laboratory in Batavia, Illinois, discovered what became known as the bottom quark in 1977, they figured it’d just be a matter of time before they discovered that particle’s partner piece, predicted by the Standard Model of Particle Physics.
They were wrong. It would take an effort by hundreds of scientists from 13 nations and the construction of two powerful particle detectors to hunt down the top quark.
Over the next few years, two teams of 450 scientists each began accelerating and colliding protons and antiprotons in the Tevatron, an underground particle accelerator buried in a circular tunnel 4 miles around.
One of the two detectors that were used to find the top quarks produced by Fermilab's Tevatron. Source: Fermilab
They took careful measurements of the results: They knew that top quarks wouldn’t last long after they were created — in less than one septillionth of a second, they’d decay, releasing a shower of other particles and very specific energies that can be detected and recorded.
So those in the lab couldn’t see a top quark when one was formed. No alarms went off. No “eureka” moment. Instead, top quarks were detected by sifting through reams of data long after the fact.
“No single piece of evidence, no matter how strong, was enough to let us claim a discovery,” explained physicist Nick Hadley of the University of Maryland. “We couldn't be sure we had found the top quark until we had seen so many events with the right characteristics that there was almost no chance the statistics were fooling us into making a false claim."
On Feb. 24, 1995, the two teams submitted papers to the scientific journal Physical Review Letters, describing confirmation of their observations of the top quark. A news conference was held to announce the discovery on March 2 and the papers were published in the April 3 issue of Physical Review Letters.
Naturally, there was still work to do: search for yet another elusive piece of the particle physics puzzle, the Higgs boson — sometimes called the “God Particle.” It was finally detected in 2012 at the Large Hadron Collider near Geneva, Switzerland.
Scientists pack an auditorium at Fermilab on March 2, 1995, to hear about the discovery of the top quark. Source: Fermilab
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