Top Quark Cross Sections

The top quark is the latest quark of the Standard Model (SM) that was discovered, discovery that was made in 1995 by the CDF and D0 collaborations [1]. It is the “youngest” quark of the SM and many of its properties remain to be studied in detail. Since it is also the heaviest elementary particle known so far, its status in the SM is special. Indeed, the top quark is 40 times heavier than its weak isospin partner the b quark and its Yukawa coupling to the Higgs boson is close to 1. The large top quark mass induces large contributions in virtual fermionic loops of radiative corrections. Since its decay time is smaller than the hadronization time, the top quark is the only quark that decays before hadronizing and so it can be used to probe the properties of a bare quark. All these characteristics may indicate that the top quark could play a special role in the SM. Top physics is a rich and still developping field in particular at the Tevatron, the proton-antiproton collider at Fermilab with a center of mass energy of 1.96 TeV, which is currently the only place where the top quark can be produced directly. Two multipurpose detectors are located around the Tevatron accelerator: CDF D0. The Tevatron running period can be divided into three data taking periods: first the Run I from 1993 to 1996 with a center of mass energy of 1.8 TeV and a delivered integrated luminosity of 120 pb−1 per experiment, secondly the Run IIa from 2002 to March 2006 with an increased center of mass energy of 1.96 TeV and a delivered integrated luminosity of 1.5 fb−1 per experiment. Finally the third period from August 2006 is expected to last until 2009 or 2010 with an expected delivered integrated luminosity from 6 to 8 fb−1. The typical data taking efficiency of the experiments is above 85%. The analyses presented in this article use from 0.9 to 2.2 fb−1 of data and are documented in [2, 3]. The results are quoted as they were presented at the time of the conference regardless on any later updates. The top quark can be produced via two modes, either via the strong interaction leading to a production by tt pair or via the electroweak interaction leading to the single top production. The pair production is the dominant mode at hadron colliders.