The Discovery of the Top Quark

March 2nd, 1995

Today 29 years ago, the discovery of the top quark was announced by Fermilab, following an effort that took almost two decades, and which required the construction of a new particle collider, the Tevatron. Its discovery finally put what is called the “standard model of particle physics” on a solid experimental ground.

The top quark is an elementary particle. Consider that we call the fundamental constituents of elements “atoms”, which means “uncuttable”. But we can indeed “cut” them further into protons, neutrons and electrons. The first two can be “cut” even further into elementary particles called quarks. At this time, quarks are not considered to be “cuttable” any further.

There are six flavors of quarks, and they obey the strong force (sometimes called color force) which we do not experience in everyday life because it occurs only inside atoms. The top quark is by far the most massive, being almost 340,000 times as massive as the electron. It is also the shortest-lived, with a half-life less than one hundred thousand billion billionth of a second. In terms of its half-life, a fraction of a second is what the age of the universe is to us.