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![Page 1: James Stirling IPPP, University of Durham with acknowledgements to R Barbieri, J Ellis, D Miller (ICHEP04), M Peskin (Victoria LCW), S. Dawson, R. Heuer.](https://reader036.fdocuments.in/reader036/viewer/2022062407/56649e365503460f94b261bb/html5/thumbnails/1.jpg)
James Stirling
IPPP, University of Durham
with acknowledgements to R Barbieri, J Ellis, D Miller (ICHEP04), M Peskin (Victoria LCW), S. Dawson, R. Heuer
The International Linear Collider
– an overview of the physics motivation and theory
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ECFA Workshop 2WJ Stirling
the most up-to-date reference…
The LHC-LC Study Group Report
Georg Weiglein et al.
www.ippp.dur.ac.uk/~georg/lhclc/
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ECFA Workshop 3WJ Stirling
Particle Physics 2004
gauge sector
mass sector
EWSB sector
flavour sector
… and beyond?… and beyond?
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ECFA Workshop 4WJ Stirling
Particle Physics 2004
gauge sector
mass sector
EWSB sector
flavour sector
… and beyond?… and beyond?
QCD 1
?pentaquarks
QCD 2
CKM
EWSB
mass
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ECFA Workshop 5WJ Stirling
2.7
g-2
discrepancies?
NuTeV
LEPEWWG 2004
?
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ECFA Workshop 6WJ Stirling
limits?
t
S Z
+ 69H - 4
2
5
H
m = 178.2 3.9 GeV
(M ) = 0.1186 0.0027
m = 114
= 15.8/13 df (prob = 2
GeV
m < 260 GeV (
6
95 )
%)
% cl
Higgs
SUSYdark matter
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ECFA Workshop 7WJ Stirling
the key questions
1) What is the origin of mass? Is it the Higgs mechanism or …?
2) What is the origin of the matter-antimatter asymmetry in the universe?
3) What are the properties of neutrinos?
4) Is there unification of particles and forces including gravity?
5) What is the dark matter?
particle physics
2) present and future B Factories3) solar, atmospheric, reactor, (super)beam, 0,
…, NuFact experiments1), 4), 5) high-energy colliders: Tevatron, LHC, ILC
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ECFA Workshop 8WJ Stirling
key issue: electroweak symmetry breaking
• Supersymmetry (MSSM and variants)
• Higgs as Pseudo Goldstone Boson
• Composite Higgs
• Technicolour
• Higgsless models
• Extra dimensions
• …
Note: in all scenarios, something (or some combination of things) has to mimic a light Higgs boson in the precision electroweak (EWPO) fits!
Scenarios include:
The Calculability Principle (Barbieri):
Restrict to models in which the Fermi scale (GF-1 or MZ) can be related to
some other physical scale (NP say) in a calculable manner, i.e. MZ = NP f(ai) where the ai are physical parameters. Then
CP consistency with data SUSY, Higgs as PGB
+ gauge unification+ dark matter candidate+ ‘naturally’ consistent with PEW data
but…• where is the Higgs?• where are the superpartners?• “little hierarchy” problem!
then…NMSSM with heavier h0 , more neutral
scalars etc.
Little Higgs Models
• embed SM in large gauge group• Higgs as PGB
• in mh2 cancel top loop with new heavy T quark
• new quarks, gauge bosons, Higgs bosons in the 1 – 10 TeV range
but…• too many such models?• too ad hoc?
nevertheless…at the very least, a useful “straw-man” alternative to SUSY!
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ECFA Workshop 9WJ Stirling
what LHC can do: SM-like Higgs
fb-1
LHC: ATLAS
1 year @1033
1 year @1034
1 month @1033
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ECFA Workshop 10WJ Stirling
what LHC can do: SUSY
Higgses sparticles
whole plane covered for at least one Higgs (but note large “only h” region!)
squark and gluino masses eventually up to ~2.5 TeV
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ECFA Workshop 11WJ Stirling
however…• ‘hadro-philic’ bias in new physics searches (gg,qq X)
• large SM backgrounds always a problem (Higgs< total 10-9)
• EWPO: only modest improvement over Tevatron (mtop , mW )
• no longitudinal momentum balance; ‘missing pT’ for invisible particles is relatively crude tool; quark flavour tagging difficult
• strong model dependence of new physics analyses:
conventional SUSY
neutrino LSP (Murayama et al)
‘bosonic supersymmetry’ (Cheng, Matchev, Schmaltz)
multiple hypotheses, distinguished by different spin and energy flows, difficult to distinguish at LHC
Peskin (Victoria, 2004)
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ECFA Workshop 12WJ Stirling
cross sections: LHC vs. ILC
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ECFA Workshop 13WJ Stirling
ILC physics summarywhatever the scenario unveiled by Tevatron & LHC, ILC has an essential role to play
• continue with precision electroweak measurements (in particular, mtop )
• if a light Higgs exists, measure its properties (mass, couplings to fermions & gauge bosons, self-couplings, …)
• if LHC reveals other light ( e.g. SUSY) particles, measure the spectrum and properties
• if LHC reveals no light particles, explore the ~1 TeV region through precision measurements sensitive to virtual new physics
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precision
current MW
Heinemeyer et al (LHCLC report)
mW (MeV) mtop
(GeV)sin2eff10
5
now 34 3.9 17
TeV Run 2 16 1.4 29
LHC 15 1-2 14-20
ILC-GigaZ 7 0.1 1.3
MW = cosw MZ [ 1 + α F(mt,MH,SUSY,..)+ …]
W
H
b
+
t
+ …
Heinemeyer, Weiglein 04
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ECFA Workshop 15WJ Stirling
precision contd.
Heinemeyer et al 2003
precision EW measurements complement direct new physics measurements
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ECFA Workshop 16WJ Stirling
Key questions• precise mass?• couplings to other particles – SM or not?• self-couplings?• other higgses?
Higgs physics at ILC
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Key questions• precise mass?• couplings to other particles – SM or not?• self-couplings?• other higgses?
Higgs physics at ILC
compare with
)(
)(
hBR
bbhBRR
Example:
Guasch, Hollik, Penaranda 2003
also ttH coupling measurements – see LHCLC report
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ECFA Workshop 18WJ Stirling
Key questions• precise mass?• couplings to other particles – SM or not?• self-couplings?• other Higgses?
Higgs physics at ILC
V() = ½ mh2 2 + 3 v 3 + ¼ 4
4
in SM: 3 = 4 = ½ mh
2 v-2
3 / 3 ~ 20%
h
h
Z*e
e
Z
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ECFA Workshop 19WJ Stirling
supersymmetry at the ILCthe task:
• determination of kinematically accessible sparticle spectrum
• measure sparticle properties (masses, cross sections, JPC)
• use these (with complementary information from LHC) to constrain underlying SUSY model
• extrapolate to GUT scale using RGEs
the techniques:
• end point spectra
• threshold scans
• + e-e-, e, polarised beams
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*
*+
++
+ **
- -
+
***
* Needs > 500 GeV. (Also < 500 study in LHC/LC)
+ e+e- threshold scan.- e-e- threshold scan (s-wave allowed)
David Miller, ICHEP04
example of a global MSSM spectrum fit
LSP
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see e.g. LHCLC report for details, many more examples, and references
the LHC-LC synergy: using precisely measured LSP mass at ILC to constrain LHC measurements of slepton and squark masses
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ECFA Workshop 22WJ Stirling
… then on to the GUT scale!
Allanach, Blair, Kraml, Martyn, Polesello, Porod,,Zerwas
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ECFA Workshop 23WJ Stirling
… and if nothing below 500 GeV?W
h
b
+
t
+ ?
little Higgsheavy Higgsno Higgs…
a generic feature of such models is heavy s-channel resonances in the 1-3 TeV range
(new gauge bosons, technipions, KK resonances, …)
e
e
W
W
Z’e
e
f
f
Z’e
e
WL
WL
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ECFA Workshop 24WJ Stirling
ILC (eeff)LHC (direct)
sensitivity to new heavy Z’sensitivity to new heavy
resonances in ee WW
M = 1.9 TeVSM couplings (a=1)LC: 500 GeV, 500 pb-1
LHC
LC
assume a1=1
Richard 2003
Barklow et al, LHCLC report
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Summary of the case for the TeV ILC
1. Definite; mt<100MeV
2. If there is a light Higgs
3. and extra particles
4. If LHC sees nothing newbelow ~ 500 GeV mass
Vital constraint.Increasingly sure
it can be done.
LHC probably sees.ILC shows what it is.
LHC and ILC needed topin down model, identify DM(?),
extrapolate to GUT scale.
Then LHC + ILC point to CLIC, andmaybe superLHC
ILC looks beyondLHC’s direct reach
David MillerICHEP04