CERN-THESIS-2012-153 26/07/2012 - CERN Document Server

Chapter 2
Top Quark Physics
2.1 Introduction
In 1994 first hints of the top quark were reported by the CDF experiment [9]. Later in 1995 its existence
was corroborated by both CDF and D0 experiments [10,11] at the Tevatron. Its discovery completed the
three generation structure of the SM and signaled the start of the new field of top quark physics. Some of
its properties, like its rather large mass, make it a very interesting object of study, not only for the under-
standing of the SM, but also in the search of physics beyond the SM (BSM). This chapter briefly covers the
theoretical background relevant for this analysis. In particular, Section 2.3 covers aspects of the top quark,
like production and decay, that will be referred to in the following. Section 2.4 reviews FCNCs, not only
within the SM, but also in some extensions of the SM.
2.2 The Standard Model
The introduction of the SM [12–15] made one of the recurrent dreams of elementary particle physics possible:
a fundamental synthesis between electromagnetism and weak interactions 1 . Strong interactions were later
described by introducing quantum chromodynamics, and the existence of quarks confirmed in 1974 with the
discovery of J/ψ. The following summary is taken from References [16–20].
At present, the SM of particles and their interactions account for practically all the experimental data
from high energy physics experiments. Within this model, all particles are built from a number of funda-
mental, spin 1
2 , particles called fermions (quarks and leptons), summarized in Table 2.1. For each of these
fermions, there exists an antiparticle with the same mass but opposite charge. Neutrinos ν have been re-
cently observed to have non-zero mass, unlike previously assumed. Furthermore, because they are neutral,
1 Quoting A. Salam from Reference [13].
3