16
2 Phenomenology of Jet Substructure
bb
58.1%
cc
2.9 %
6.3 %
0.02%
WW*
21.5%
ZZ*
2.6 %
gg
8.2 %
0.23%
Zγ
0.15%
γγ
Fig. 2.4 Higgs decay branching fractions in the SM for m H = 125.09 GeV. Taken from [139]
Table 2.1 Branching fractions of the H boson in the SM together with total theoretical uncertainties [137, 138], obtained for m H = 125.09 GeV
2.2.5 Top Quark Decay
The top quark was discovered in 1995 by the CDF and D0 experiments at Fermilab [31, 32]. With a mass of m t = 173.34 ± 0.76 GeV [140] it is the heaviest
particle in the SM. The dominant decay is t → W b, where the W d and W s decays
are Cabibbo suppressed by the squares of the CKM matrix elements V td and V ts .
Assuming validity of the SM and unitarity of the CKM matrix implies a value of
V tb > 0.999 [78] and therefore a branching fraction B t→W b close to unity. The total
width is t = 1.34 ± 0.01 GeV, calculated including finite b quark mass effects,
finite width effects [141, 142], one and two-loop QCD corrections [141, 143–146],
and one-loop EW corrections. The large width implies a short lifetime of the top
quark τ = 1/ / t , which is about an order of magnitude smaller than the typical for-
2 Phenomenology of Jet Substructure
bb
58.1%
cc
2.9 %
6.3 %
0.02%
WW*
21.5%
ZZ*
2.6 %
gg
8.2 %
0.23%
Zγ
0.15%
γγ
Fig. 2.4 Higgs decay branching fractions in the SM for m H = 125.09 GeV. Taken from [139]
Table 2.1 Branching fractions of the H boson in the SM together with total theoretical uncertainties [137, 138], obtained for m H = 125.09 GeV
2.2.5 Top Quark Decay
The top quark was discovered in 1995 by the CDF and D0 experiments at Fermilab [31, 32]. With a mass of m t = 173.34 ± 0.76 GeV [140] it is the heaviest
particle in the SM. The dominant decay is t → W b, where the W d and W s decays
are Cabibbo suppressed by the squares of the CKM matrix elements V td and V ts .
Assuming validity of the SM and unitarity of the CKM matrix implies a value of
V tb > 0.999 [78] and therefore a branching fraction B t→W b close to unity. The total
width is t = 1.34 ± 0.01 GeV, calculated including finite b quark mass effects,
finite width effects [141, 142], one and two-loop QCD corrections [141, 143–146],
and one-loop EW corrections. The large width implies a short lifetime of the top
quark τ = 1/ / t , which is about an order of magnitude smaller than the typical for-