6 The Discovery of the Higgs Boson at the LHC
267
to exist with one resembling the SM Higgs boson with a mass below about 140 GeV.
The lightest of this new species of superparticles could be the candidate for dark
matter whose presence, by mass, in the universe is around five times more abundant
than ordinary matter.
In 1975, physicists had already started to turn their attention to how a putative
Higgs boson would manifest itself in experiments [27].
The search for the SM Higgs boson provided a stringent benchmark for evaluating the physics performance of various experiment designs under consideration in
the early 1990s and heavily influenced the conceptual design of the general-purpose
experiments, ATLAS and CMS.
6.2.1 Higgs Boson: Production and Decay
Although the mass of the Higgs boson is not predicted by theory, at a given mass all
of its other properties are precisely predicted within the SM. The SM Higgs boson
is short-lived (10 −23 s) and hence the experiments only detect the decay products.
The cross sections for differing production mechanisms and the branching
fractions for differing decay modes of the SM Higgs boson, as a function of
mass, are illustrated in Fig. 6.2a, b, respectively [28], and the principal ones for
m H = 125 GeV and at
√
s = 14 TeV are tabulated in Table 6.1. The uncertainties
on these numbers can be found in the twiki in Reference [28].
[TeV]
s
6 7 8 9 10 11 12 13 14 15
H+X) [pb]
(pp
2
10
1
10
1
10
2
10
M(H)= 125 GeV
LHC HIGGS XS WG 2016
H (N3 LO QC D + NLO EW )
pp
qqH (NN LO QC D + NLO EW )
pp
WH (NN LO QCD + NLO EW)
pp
ZH (NN LO QCD + NLO EW)
pp
ttH (N LO QC D + NL O EW )
pp
bbH (NN LO QCD in 5FS , NLO QCD in 4FS )
pp
tH (N LO QC D, t-c h + s-c h)
pp
[GeV]
H
M
120 121 122 123 124 125 126 127 128 129 130
Branching Ratio
-4
10
-3
10
-2
10
-1
10
1
LHC HIGGS XS WG 2016
b
b
c
c
gg
ZZ
WW
Z
(a)
(b)
Fig. 6.2 (a) SM Higgs boson production cross sections as a function of the centre-of-mass energy,
√ s, for pp. collisions. The VBF process is indicated here as qqH [28]. The theoretical uncertainties
are indicated as bands. (b) Branching ratios for the main decays of the SM Higgs boson near
m H = 125GeV [28]. The theoretical uncertainties are indicated as bands
267
to exist with one resembling the SM Higgs boson with a mass below about 140 GeV.
The lightest of this new species of superparticles could be the candidate for dark
matter whose presence, by mass, in the universe is around five times more abundant
than ordinary matter.
In 1975, physicists had already started to turn their attention to how a putative
Higgs boson would manifest itself in experiments [27].
The search for the SM Higgs boson provided a stringent benchmark for evaluating the physics performance of various experiment designs under consideration in
the early 1990s and heavily influenced the conceptual design of the general-purpose
experiments, ATLAS and CMS.
6.2.1 Higgs Boson: Production and Decay
Although the mass of the Higgs boson is not predicted by theory, at a given mass all
of its other properties are precisely predicted within the SM. The SM Higgs boson
is short-lived (10 −23 s) and hence the experiments only detect the decay products.
The cross sections for differing production mechanisms and the branching
fractions for differing decay modes of the SM Higgs boson, as a function of
mass, are illustrated in Fig. 6.2a, b, respectively [28], and the principal ones for
m H = 125 GeV and at
√
s = 14 TeV are tabulated in Table 6.1. The uncertainties
on these numbers can be found in the twiki in Reference [28].
[TeV]
s
6 7 8 9 10 11 12 13 14 15
H+X) [pb]
(pp
2
10
1
10
1
10
2
10
M(H)= 125 GeV
LHC HIGGS XS WG 2016
H (N3 LO QC D + NLO EW )
pp
qqH (NN LO QC D + NLO EW )
pp
WH (NN LO QCD + NLO EW)
pp
ZH (NN LO QCD + NLO EW)
pp
ttH (N LO QC D + NL O EW )
pp
bbH (NN LO QCD in 5FS , NLO QCD in 4FS )
pp
tH (N LO QC D, t-c h + s-c h)
pp
[GeV]
H
M
120 121 122 123 124 125 126 127 128 129 130
Branching Ratio
-4
10
-3
10
-2
10
-1
10
1
LHC HIGGS XS WG 2016
b
b
c
c
gg
ZZ
WW
Z
(a)
(b)
Fig. 6.2 (a) SM Higgs boson production cross sections as a function of the centre-of-mass energy,
√ s, for pp. collisions. The VBF process is indicated here as qqH [28]. The theoretical uncertainties
are indicated as bands. (b) Branching ratios for the main decays of the SM Higgs boson near
m H = 125GeV [28]. The theoretical uncertainties are indicated as bands