Top Quarks Go Solo in Rare Events

• DOI: 10.1103/physics.7.61
• Publication Date: 2014-06-09T21:26:31Z
• Authors: Richard Hawkings
• Keywords: 0103 physical sciences; 7. Clean energy; 01 natural sciences

The subatomic elementary particles known as quarks are among the building blocks of the standard model (SM) of particle physics. Protons and neutrons are made of the lightest, up and down quarks, but the unstable strange, charm, bottom, and top quarks can also be produced in high-energy particle accelerators. The enigmatic top quark—which is the heaviest elementary particle, weighing as much as a gold nucleus—has only been studied at Fermilab’s Tevatron collider near Chicago and at the Large Hadron Collider at CERN, Geneva. It is most often produced with its antiparticle (antitop) through the strong interaction, but it also appears singly through the electroweak interaction, as was demonstrated in 2009 [1, 2]. Two new papers in Physical Review Letters [3, 4] report the first observations of single top quarks coming out of less common electroweak reactions, or “channels.” The results fall within SM predictions, but further studies of the relative frequency of these rare channels may reveal new physics, such as a hidden generation of quarks or unexpected top-quark couplings.