Top quark physics in hadron collisions

Abstract

The top quark is the heaviest elementary particle observed to date. Its large mass makes the top quark an ideal laboratory to test predictions of perturbation theory concerning heavy quark production at hadron colliders. The top quark is also a powerful probe for new phenomena beyond the Standard Model of particle physics. In addition, the top quark mass is a crucial parameter for scrutinizing the Standard Model in electroweak precision tests and for predicting the mass of the yet unobserved Higgs boson. Ten years after the discovery of the top quark at the Fermilab Tevatron top quark physics has entered an era where detailed measurements of top quark properties are undertaken. In this review article an introduction to the phenomenology of top quark production in hadron collisions is given, the lessons learned in Tevatron Run I are summarized, and first Run II results are discussed. A brief outlook to the possibilities of top quark research a the Large Hadron Collider, currently under construction at CERN, is included.PACS numbers: 14.65.Ha Summary and outlook 79Top quark physics in hadron collisions 4 IntroductionThe top quark is the by far heaviest of the six fundamental fermions in the Standard Model (SM) of particle physics. Its large mass made the search for the top quark a long and tedious process, since accelerators with high centre-of-mass energies are needed. In 1977 the discovery of the bottom quark indicated the existence of a third quark generation, and shortly thereafter the quest for the top quark began. Searches were conducted in electron-positron (e + e − ) and protonantiproton (pp) collisions during the 1980s and early 1990s. Finally, in 1995 the top quark was discovered at the Fermilab Tevatron pp collider. Subsequently, its mass was precisely measured to be M top = (178.0 ± 4.3) GeV/c 2 [1]. The relative precision of this measurement (2.4%) is better than our knowledge of any other quark mass. The top quark is about 40 times heavier than the second-heaviest quark, the bottom quark. Its huge mass makes the top quark an ideal probe for new physics beyond the SM.It remains an open question to particle physics research whether the observed mass hierarchy is a result of unknown fundamental particle dynamics. It has been argued that the top quark could be the key to understand the dynamical origin of how particle masses are generated by the mechanism of electroweak symmetry breaking, since its mass is close to the energy scale at which the break down occurs (vacuum expectation value of the Higgs field = 246 GeV) [2]. The most favoured framework to describe electroweak symmetry breaking is the Higgs mechanism. The masses of the Higgs boson, the W boson and the top quark are closely related through higher order corrections to various physics processes. A precise knowledge of the top quark mass together with other electroweak precision measurements can therefore be used to predict the Higgs boson mass. At present, top quarks can only be directly produced at the Tevatron. The physics results of the Tevat...

Next-to-leading order QCD effects and the top quark mass measurements at the LHC

“…(34). We use CTEQ parton distribution functions [28,29] Although this is not an extensive scan of the parameter space, it gives a sense of theoretical uncertainties in m Bl provided that realistic production mechanism is employed 6 . Computing the mean and the error, we arrive at the results shown in Table 3.…”

“…ATLAS and CMS plan to employ a variety of methods for measuring the top quark mass [3,4,5,6,7,8]. These methods can be divided into two classes.…”

Identification of electrons in the forward region of the CDF experiment for the search for electroweak top quark production

“…For an in-depth introduction to the Standard Model, I would like to point the reader to textbooks like references [1,2,3]. Reference [4] is an overview article which focuses on top quark physics in hadron colliders.…”

Search for Electroweak Single-Top Quark Production with the CDF II Experiment

“…Afterwards the single-top production via the electroweak force is discussed in more detail. A detailed review on top quark physics can be found in reference [14].…”