Top quark physics in hadron collisions

TL;DR

The article surveys top-quark physics in hadron collisions within the Standard Model, emphasizing the top quark’s role as a probe of perturbative QCD, electroweak precision tests, and potential new phenomena. It details the theoretical framework for top production at hadron colliders, including $t\bar t$ production via QCD with LO/NLO accuracy and soft-gluon resummation, and the three single-top channels via the $Wtb$ vertex, highlighting the governing dependence on $M_ op$ and PDFs. The work connects top-mass measurements to electroweak fits and Higgs-boson mass constraints, showcasing how precision data from LEP/SLD and Tevatron measurements constrain the SM and guide Run II and LHC prospects. It also discusses experimental considerations for detecting top events and for interpreting cross sections in light of PDFs, scales, and higher-order corrections. Overall, the review provides a cohesive synthesis of theory–experiment interplay in top-quark production and properties, with concrete cross-section predictions and implications for the Higgs sector and beyond-SM physics.

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.

Figures (12)

• Figure 1: (a) An example of a fermion triangle diagram. (b,c) Two example Feynman diagrams of radiative corrections involving the top quark. (b) is a radiative correction to the $Z^0$ propagator. (c) shows a vertex correction to the decay $Z^0 \rightarrow b\bar{b}$.
• Figure 2: Results of fits to electroweak data lepewwg2004. Direct Higgs boson searches at LEP2 and the top mass measurement at the Tevatron are summarised in these plots. (a) shows the plane "top mass versus Higgs mass". The light shaded area is excluded by direct searches for the Higgs boson at LEP2. The dark shaded area is given by the central value of the direct top mass measurement at the Tevatron and its errors. The dashed line encloses the region preferred by the electroweak data at 68% confidence level. (b) shows the "$M_W$ versus $M_\mathrm{top}$" plane. The full line encloses the area preferred by the SM fit to data from LEP1 and SLD. The dashed contour indicates the result of the LEP2, UA2 and Tevatron $W$ mass measurements and the direct top quark mass measurement. The plot also shows the SM relationship of the masses as function of the Higgs boson mass.
• Figure 3: Examples of loop diagrams of the $W$ propagator introducing a dependence of the $W$ mass on the top and Higgs mass.
• Figure 4: Lowest order Feynman diagrams for B meson mixing. A $\overline{B^0}\;(b \bar{d})$ or a $\overline{B^0_s}\;(b \bar{s})$ oscillates into a $B^0\;(\bar{b} d)$ or a $B^0_s\;(\bar{b} s)$, respectively.
• Figure 5: Parton distribution functions (PDFs) of $u$ quarks, $\bar{u}$ quarks, $d$ quarks, $\bar{d}$ quarks and gluons inside the proton. The parametrization is CTEQ3M lai1995. The scale at which the PDFs are evaluated was chosen to be $\mu=175\;\mathrm{GeV}$ ($\mu^2 = 30625\;\mathrm{GeV^2}$).