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

List of Figures
2.1 The potential V (φ) for a complex scalar field φ = (φ1 + iφ2)/ √ 2 for µ 2 < 0 and λ > 0. The
circle of minima has a radius v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 Decay modes of the W- and Z-bosons. In the case of the W-boson, the lepton ℓ carry the
same charge as the boson. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 Summary of measurements of the top quark mass by the (a)ATLAS and the (b) CMS experiment.
In both cases, 2011 pp collision data at a center of mass energy of √ s = 7 TeV were
used. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4 Feynman diagrams for top production processes at lowest level: (a), (b), and (c) gluon-gluon
scattering diagrams, (d) quark-antiquark diagram. . . . . . . . . . . . . . . . . . . . . . . . . 15
2.5 Summary of measurements of the t¯t cross section by the (a)ATLAS and the (b) CMS experiment.
In both cases, 2011 pp collision data at a center of mass energy of √ s = 7 TeV were
used. The combination of the different channels is σt¯t = 177 ± 3(stat.) +8
−7
(syst.) ± 7(lumi.) pb
for ATLAS [21] and σ t¯t = 166 ± 2(stat.) ± 11(syst.) ± 8(lumi.) pb for CMS [22]. . . . . . . . . 16
2.6 Feynman diagrams of Top quark decays. The FCNC deays in the SM are not present at tree
level, thus the diagrams presented here are just for illustration. . . . . . . . . . . . . . . . . . 16
2.7 Example of a higher order loop diagram allowed in the SM. In these diagrams di can be either
of the three down-type quarks. Thus, in each case there are possible three diagrams. . . . . 18
2.8 (a) Reconstructed top quark mass distribution, m reco
t , of data, FCNC t¯t signal, and expected
background for events with njet ≥ 1 from the FCNC search performed by D0 experiment [4].
(b) Mass χ 2 distribution for signal regions with (b-tagged) and without (anti-tagged) an
identified b-jet and the control region from the CDF search of FCNC in top quark decays [57]. 20
2.9 Summary of several Standard Model total production cross section measurements performed
by the ATLAS experiment compared to the corresponding theoretical expectations. The error
bars include the full uncertainty, both statistical and systematic. All theoretical expectations
were calculated at NLO or higher. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1 The LHC injection complex. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2 Cut-away view from the ATLAS detector [64]. . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3 ATLAS Detector components overview: (a) Magnet system, (b) Inner detector, (c) EM and
hadronic calorimeters, and (d) Muons spectrometer [64]. In (a) the eight barrel toroid coils,
with the end-cap coils interleaved are visible. The solenoid winding lies inside the calorimeter
volume. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1 Some relevant kinematic quantities for different TopRex coupling values for the t → qZ
channel: mass of the top quark (a) with FCNC decay and (b) with SM decay; transverse
momenta distributions of (c) the FCNC decaying top quark, (d) the SM decaying top quark,
(e) the b-quark from SM decaying top quark, (f) the quark and the (g) Z from the FCNC
decaying top quark, (h) the W boson from the SM decaying top quark and i) the decay
products of the Z boson. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
x