Single Top at Hadron Colliders

Abstract

At hadron colliders, the strong production of $t\bar t$ pairs yelds large top quark samples, allowing detailed studies of many properties of top quark production and decay. However, the precise determination of the properties of the Wtb vertex, and the associated coupling strenghts, will more likely be obtained from measurements of the electroweak production of single top quarks. Single top quarks can be produced via three different reactions. These reactions are shown in Fig. 1 from left to right. The first two graphs, usually referred to as the 2 → 2 and 2 → 3 processes, respectively, both refer to the same physical W-gluon fusion process. The second production mechanism (the third graph from the left), referred to as the Wt process, is the direct production of a top quark and a W boson. This process is immeasurably small at the Tevatron, but is predicted to have a sizeable cross-section (≈ 60–110 pb) at the LHC. The third reaction proceeds via production of an off-shell W and will be called the W* process.