Scientists Make Largest Quark, Solving A 20-Year Mystery

Researchers have found the "final" predicted way of making top quarks, the largest subatomic particle.

Fermilab
Fermilab, Reidar Hahn

Top quarks are the heaviest of subatomic particles, and are prime components of all matter--everything from mayonnaise to your big toe. But while they are in virtually everything, they are impossible to isolate from matter under ordinary circumstances. To study them, you need to "make" them by running particles into each other at ultra-high speeds, billions or trillions of times.

After working at it for nearly 20 years, scientists at the Tevatron particle accelerator at Fermilab have discovered the last as-yet-unproven way of making this quark--and it only took 500 trillion particle collisions to do it. "It's a very rare process... and it's very exciting" to finally witness it, Fermilab physicist Dmitri Denisov told Popular Science.

Under the Standard Model, the theory by which these particles are understood, there should be three ways of producing quarks. The first two had been shown in 1995 and 2008. In the first instance, top quarks were produced by strong nuclear force, by slamming a proton and anti-proton into each other. But in the 2008, and now the 2014 discovery, top quarks were produced in a rare event, via weak nuclear force. The finding helps reinforce the Standard Model, which predicts that quarks can be made by exploiting both types of forces, Denisov said. "It's important that all forces in nature, strong and weak, equally produce the top quark."

"My prediction is that at some point, knowing how to make this particle will also be useful for something 'next step,' " like perhaps energy production, Denisov speculated.

The actual particle collisions that made the quark took place prior to Tevatron's closure in 2011, but were only uncovered and announced in a statement today (Feb. 24) after years of analyzing massive amounts of data produced by the accelerator.