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."