quark
From ars technica, Feb. 29, 2016: Fermilab’s found a brand-new species—the first particle with four flavors of quarks.
From Scientific American, Feb. 26, 2016: Evidence for a never-before-seen particle containing four types of quark has shown up in data from the Tevatron collider at Fermilab.
From Gizmodo, Feb. 25, 2016: Physicists from the DZero collaboration have announced the discovery of a new particle, believed to be part of an exotic family called “tetraquarks.”
There are a lot of mysteries in particle physics, but one of the most curious is called the flavor problem. Physicists use the word flavor to mean the different varieties of particles. As readers of this column will recall, there are six types of quarks: up and down, charm and strange, and top and bottom. Up and down quarks are found in ordinary matter and are called generation I. The other two generations are very similar in their properties compared…