Main.dvi• The missing piece in a spectacularly successful theory construct:
the “Standard Model” of the fundamental interactions
• A massive experimental program to validate our (50 year old)
picture of the Electroweak Symmetry Breaking (EWSB)
spanning four generations of large colliders
and their associated detectors
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Quote: Lev Okun – closing talk Lepton-Photon 1981
Instead of giving a general overview of the prospects, I decided to choose
and discuss in some details just one problem, which could be considered
as problem No. 1 in particle physics. To be No. 1 this problem has to
be theoretically advanced and urgent. It should also be experimentally
accessible.
It seems to me that the problem No. 1 of high energy physics are scalar
particles. Painstaking search for light scalars should be considered as the
highest priority for the existing machines ... and even more so for the
next generation of accelerators ...
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Quote: M. Peskin – closing talk Lepton-Photon 2011
A project of the magnitude of the LHC can only be created by an organi-
zation that goes beyond the usual human scale. Of course, it takes billions
of dollars, huge technological expertise, and much effort in construction.
But it requires more.
The LHC was imagined in the early 1980s, and not realized until the
2010s. It required an institution whose goals could be coherent over that
time period – more than a generation – constantly working with govern-
ments and the scientific community to move the project forward.
It is a unique achievement. Our whole community must be grateful to
CERN as an institution for making it possible.
Arthur Maciel, C. Jordao, SP (Jan. 2013) 2
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Is it the Higgs boson ?
Needs identity tests,
e.g. spin, parity,
couplings to fermions...
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14 December 2012
The United Nations General Assembly in New York today adopted a
resolution granting CERN observer status. This status gives the Organi-
zation the right to participate in the work of the General Assembly and
to attend its sessions as an observer.
”It’s a great honour for CERN to accede to the status of observer at
the UN General Assembly”, said CERN Director-General, Rolf Heuer.
”CERN has a long tradition of close cooperation with the United Nations
and its agencies, which dates back to 1954 when the Laboratory was
founded under the auspices of UNESCO”.
Arthur Maciel, C. Jordao, SP (Jan. 2013) 4
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• P & S book page 750φ plane
µ2 φ φ + λ ( φ φ )2
v
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• And, jumping over to the late 90’s at LEP,
finally, observation of e+e− −→ W+W−
(a) (b)
(c) (d)
e+ e–
e– e–
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– three gauge interaction diagrams
(pure J=1 amplitudes)
– but the divergences cancel out in the sum
– a major experimental test for (non-abelian)
trilinear gauge couplings at work...
• Compare this process with νeνe → W+W−
(a) (b)
(c) (d)
e+ e–
e– e–
• If you consider e’s (with mass), the “weird” e −
R and e
Arthur Maciel, C. Jordao, SP (Jan. 2013) 7
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LEP PRELIMINARY
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J = 0 amplitudes also exist (e+ L e− R
−→ W+ W−
– but with unacceptable H.E. behavior
M (J=0) diverges ∼ √ s
• This is the amplitude associated with the
production of longitudinally polarized W ’s
• This residual divergence is canceled exactly
by the H → e+e− and H → W+W− vertices.
Note the me dependence in
f
f
h
mf/v
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(a) (b)
(c) (d)
e+ e–
e– e–
fore exist in mixtures of (eL) and (eR)
components), a J = 0 partial wave exists
– which diverges as √
(e+e−−→W +
bounds, only slower, at much higher en-
ergies (∼a few TeV ).
added neutral scalar boson exchange (d),
provided its couplings are proportional to the
masses of the particles to which it couples.
• In other words, it must be a Higgs-like
scalar boson.
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(a) (b)
(c) (d)
e+ e–
e– e–
tional to the fermion masses and it is there-
fore necessary that the S-wave “cure” also
be proportional to mass.
such that the potential problems created
by the addition of a scalar Higgs boson are
cured by its own coupling properties.
• This is a general result: the only theories
of massive vector bosons with acceptable
high energy limit behaviour are those that
result from “spontaneously broken gauge
theories”.
Arthur Maciel, C. Jordao, SP (Jan. 2013) 11
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...we need all the hints we can get...
Arthur Maciel, C. Jordao, SP (Jan. 2013) 12
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• MW = 80385 ± 15 MeV
• Mt = 173.2 ± 0.9 GeV
Arthur Maciel, C. Jordao, SP (Jan. 2013) 13
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m2 W =
sin2θW = 1− m2 W
GF = 1.16637(1)× 10−5GeV 2 αem(m2 Z) = 1/127.918(18)
mZ = 91.1876(21)GeV
top and Higgs loops
H
=⇒ Within the SM the top and W masses drive a strict constraint on MH
R ∼ m2 t
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• Precise knowledge of mW and mt will indirectly constrain MH
• These measurements have been
program
• mW is the limiting factor in cons-
training MH , and the observable is
mT W =
80.3
80.4
80.5
mt [GeV]
m W
Arthur Maciel, C. Jordao, SP (Jan. 2013) 15
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(arXiv:1203.0275)
(arXiv:1203.0293)
(TeVEWWG-prelim.) (GeV)Wm 80 80.2 80.4 80.6
LEP2 average 0.033±80.376
Tevatron 2009 0.031±80.420
Tevatron 2007 0.039±80.432
World average 0.023±80.399
mass known to 0.02% !
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0
15
Tevatron combination * 0.9± 173.2 0.8)± 0.6 ±( syst)± stat ±(
CDF-II MET+Jets * 2.6± 172.3 1.8)± 1.8 ±(
CDF-II track 9.5± 166.9 2.9)± 9.0 ±(
CDF-II alljets * 2.1± 172.5 1.5)± 1.4 ±(
CDF-I alljets 11.5± 186.0 5.7)±10.0 ±(
DØ-II lepton+jets 1.5± 174.9 1.2)± 0.8 ±(
CDF-II lepton+jets 1.2± 173.0 1.1)± 0.6 ±(
DØ-I lepton+jets 5.3± 180.1 3.6)± 3.9 ±(
CDF-I lepton+jets 7.4± 176.1 5.3)± 5.1 ±(
DØ-II dilepton 3.1± 174.0 2.5)± 1.8 ±(
CDF-II dilepton 3.8± 170.6 3.1)± 2.2 ±(
DØ-I dilepton 12.8± 168.4 3.6)±12.3 ±(
CDF-I dilepton 11.4± 167.4 4.9)±10.3 ±(
Mass of the Top Quark (* preliminary)July 2011
/dof = 8.3/11 (68.5%)2χ
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CERN Courier
Sept. 2012
dard Model Higgs boson (thin blue
line) or a minimal supersymmetric
(MSSM) one (green band). The blue
ellipse shows the current knowledge
on mt and mW, whereas the black
ellipse depicts what will happen if
mW becomes known to 5 MeV.
Arthur Maciel, C. Jordao, SP (Jan. 2013) 18
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[GeV]HM
tm bm
σ ZΓ ZM
- 73 +205139 - 25 + 31 97 - 24 + 30 95 - 24 + 30 95 - 34 + 74115 - 23 + 60 45 - 24 + 30 95 - 24 + 30 95 - 24 + 30 95 - 24 + 30 95 - 18 + 40 61 - 23 + 30 93 - 23 + 30 93 - 31 + 39120 - 24 + 30 91
- 25 + 31 99 - 24 + 30 98 - 25 + 31 96 - 24 + 31 96
- 25 + 48 61G fitter SM
A U
G 11
tm bm
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• LEPEWWG:
MH = 94 + 29 − 24GeV
• Pr.EW+LEPlim:
0
1
2
3
4
5
6
In yellow, the experimentally
Arthur Maciel, C. Jordao, SP (Jan. 2013) 20
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• Manifest internal consistency in the SM
– at a very rigorous and precise level,
– over various independent experimental tests
• Indicating the theoretical need for a scalar boson
– (elementary?)
Developing a
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• The various search strategies must necessarily come from a detailed
analysis of
the various decay modes
• Generate a list of distinct final states according to the choice of
observables
for combining search channels in the final result...
[ These are: light jets, heavy jets, photons, leptons (e, µ, τ), E/T (ν), HT · · · ]
Arthur Maciel, C. Jordao, SP (Jan. 2013) 22
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Detectors – Event Reconstruction
• Example reconstruction hierarchy:
1st stage 2nd stage 3rd stage 4th stage 5th stage 6th stage
em e c W t physics
jet γ b Z H
E/ T
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E ve
nt s/
0. 16
r ad
E ve
nt s/
0. 16
r ad
– use [V-A] properties on scalar W+W− system
(+− strong angular correlation differentiates
higgs decays from background physics)
ν
←− W+
=⇒ +
Other discriminants:
Arthur Maciel, C. Jordao, SP (Jan. 2013) 27