Physics%20topics%20at%20the%20Linear%20Collider

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Physics topics at the Linear Collider
Particle Physics Today Selected Physics
Topics ILC Options ILC/XFEL Synergy
R.-D. Heuer (Univ. Hamburg/DESY)
Linear Collider School, KEK,
2006
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History of the Universe
LHC, ILC RHIC,HERA
extrapolation via precision
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Particle Physics Todayor Status of the Standard
Model
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MatterParticles
Plus corresponding Antiparticles
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Standard Model
ee- gt Z0 gt f f where fq,l,?
resonance curve Z-Boson
sZ and GZ depend on number of (light) neutrinos
LEP

• number of families
• N 2.984 - 0.008

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Forces
type rel.strength force
carriers acts on/in
Strong Force 1 Gluons g m 0 Quarks Atomic Nucleus
Electro-magnet. Force 1/1000 Photon ? m 0 Electric Charge Atoms, Chemistry
Weak Force 10 -5 W, Z Bosons m 80 , 91 GeV Leptons, Quarks Radioactive Decays (ß-decay)
Gravitation 10 -38 Graviton ? m 0 Mass, Energy
Force Carriers (Bosons) exchange interactions
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Forces
Four fundamental Forces act between Matter
Particles through Force Carriers (Gluons, W und
Z0, ?, Graviton) forces in our energy regime
different strengths forces at high energies
democratic..unification gtSituation
immediately after creation of the
Universe
HERA
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What have we learned the last 50 yearsorStatus
of the Standard Model
The physical world is composed of
Quarks and Leptons interacting via
force carriers (Gauge Bosons)
Last entries top-quark 1995
tau-neutrino 2000
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Standard Model
mathematical description of all interactions,
involving weak, electromagnetic, strong
forces, through closely related symmetry
principles (gauge symmetries) Symmetries
are of fundamental importance for describing
the dynamics in particle physics
Noether-Theorem Symmetry ltgt Conservation
Law e.g.
Rotation
angular momentum
Mirror image
Parity
gauge transformation
charge, Baryon Local gauge symmetry
gt Invariance under local
phase transformation


(QED)
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1967/68 Glashow - Salam - Weinberg gauge theory
to unify
el.magn. and weak forces
Standard Model of electroweak interaction
Problem gauge invariance only possible for
massless gauge bosons (m0, Rgtoo
gt Phase trafo can be compensated through
gauge trafo
everywhere in space) Massive
gauge bosons gt Violation of gauge invariance
Solution Introduction of a scalar background
field (Higgs-Feld) Vacuum expectation value v
(Analogy super conductivity)
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The Higgs mechanism
Paradigm All (elementary) particles are
massless ? gauge principle works ? renormalizable
theory (finite cross sections) Permanent
interaction of particles with a scalar Higgs
fieldacts as if the particles had a mass
(effective mass)
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The Higgs mechanism
How to add such a field in a gauge invariant way?
Introduction of SU(2)xU(1) invariantMexican hat
potential Simplest case (SM) complex doublet of
weak iso-spin
This is only the most economic way. Many more
possibilitiesexist, e. g. two doublets (minimal
SUSY), triplets, ... Higgs mechanism requires the
existence of at least onescalar, massive Higgs
boson.
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Status of the Standard Model
Verification of triple gauge vertices from ee- ?
WW- cross section
Indirect determination of the top quark
mass Proves high energy reach through virtual
processes
LEP
Towards unification of forces
charged current
neutral current
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Status of the Standard Model
spring 2005
Precision measurements
1990-2005 (LEP,SLD,Tevatron,
NuTeV,) Standard Model tested to permille level
and at the level of Quantum Fluctuations Precis
e and quantitative description of
subatomic physics
However. . .
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. . . key questions open
Standard Model
What is the origin of mass of elementary
particles or why are carriers
of weak force so heavy while the photon is
massless
Higgs mechanism
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. . . key questions open
Cosmic Connections
What is dark matter What is dark energy
What happened to antimatter
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Open key questions
. . . key questions open
Ultimate Unification
Do the forces unify, at what scale Why is
gravity so different Are there new forces
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Open key questions
. . . key questions open
Hidden Dimensions
or Structure of Space -Time
Are there more than four space-time
dimensions What is the quantum theory of
gravity
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The next steps at the energy frontier
There are two distinct and complementary
strategies for gaining new understanding of
matter, space and time at future particle
accelerators HIGH ENERGY direct discovery of
new phenomena i.e. accelerators operating at
the energy scale of the new particle HIGH
PRECISION interference of new physics at high
energies through the precision measurement of
phenomena at lower scales
Both strategies have worked well together ? much
more complete understanding than from either one
alone
prime example LEP / Tevatron
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A Road Map for the Energy Frontier
Tevatron
HERA
LHC
S-LHC
ILC
CLIC, Muon collider, other technologies
2020
2010
2015
2005
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Hadron Collider Lepton Collider

• p composite particleunknown ?s of IS
  partons,no polarization of IS partons,parasitic
  collisions
• p strongly interactinghuge SM
  backgrounds,highly selective trigger
  needed,radiation hard detectors needed

• e pointlike particleknown and tunable ?s of
  IS particles,polarization of IS particles
  possible,kinematic contraints can be used
• e electroweakly interactinglow SM
  backgrounds,no trigger needed,detector design
  driven by precision

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Experimental limits on the Higgs boson mass
The next steps
We know enough now to predict with great
certainty that fundamental new understanding of
how forces are related, and the way that mass is
given to all particles, will be found with a
Linear Collider operating at an energy of at
least 500 GeV, extendable to around 1000 GeV.
LEP,SLD Tevatron
indirect
direct
MH between 114 and 250 GeV
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The power of an Electron-Positron Linear
Collider ? well defined initial state vs
well defined and tuneable quantum numbers
known polarisation of e and e-
possible ? clean environment collision of
pointlike particles ? low
backgrounds ? precise knowledge of cross
sections
options e-e-, e?, ??
ILC Machine for Discoveries and
Precision Measurements
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An Analogy What precision does for you ...
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Electron - Positron - Reactions
e-
e
Description in particle physics
l,q,W
e
Z,?
l,q,W-
e-
weak el.magn. force
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Electron - Positron - Reactions
direct measurement
indirect measurement
e
l,q,W
e
l,q,W
Z,?
e-
l,q,W-
e-
l,q,W-
Heisenberg ?E?t gt h
gt (extremely) short fluctuations
to high energies (masses) possible
(Quantum fluctuations)
Modifications of rate and properties of reactions
Effect of high masses indirectly measureable
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Precision Model
example planets
Precision measurements of Uranus orbit
gt deviation from model calculations
gt
prediction of Neptune
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Standard ModelTesting Quantum Fluctuations

• LEP
• Indirect determination of the top mass
• possible due to
• precision measurements
• known higher order electroweak corrections

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Synergy of colliders
Time evolution of experimental limits on the
Higgs boson mass
LEP,SLD, Tevatron
??top
knowledge obtained only through combination of
results from different accelerator types in
particular Lepton and Hadron Collider
indirect
direct
MH between 114 and 200 GeV
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The Role of the ILC
Explore new Physics through high precision at
high energy microscopic
telescopic
Study known SM processesto look for tiny
deviationsthrough virtual effects(needs
ultimate precisionof measurements
andtheoretical predictions)
Study the properties ofnew particles(cross
sections,BRs, quantum numbers)

• precision measurements will allow --
  distinction of different physics scenarios --
  extrapolation to higher energies

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The ILC Physics Case orRelation of Hadron
Collider and Linear Collider

• 1. Since the ILC will start after the start of
  LHC, it must add significant amount of
  information. This is the case!
• (see e.g. TESLA TDR, Snowmass report, ACFA
  study etc.)
• 2. Neither ILC nor LHC can draw the whole picture
  alone. An ILC will
• add new discoveries and
• precision of ILC will be essential for a better
  understanding of the underlying physics
• 3. There are probably pieces which can only be
  explored by the LHC due to the higher mass reach.
  Joint interpretation of the results will improve
  the overall picture
• 4. Overlapping running of both machines will
  further increase the potential of both machines
  and might be mandatory, depending on the physics
  scenario realized

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International Linear Collider Parameters
global
consensus (Sept. 2003)
(1) baseline machine 200 GeV lt vs lt
500 GeV integrated luminosity 500 fb-1
in 4 years electron polarisation
80 (2) energy upgrade to vs 1 TeV
integrated luminosity 1 ab-1 in 3
years (3) options positron polarisation
of 50 high luminosity running at MZ
and W-pair threshold e-e-, e?, ??
collisions (4) concurrent running with LHC
desired ! Times quoted for
data taking cover only part of program !
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Physics at the ILC
Comprehensive and high precision coverage of
energy range from MZ to 1 TeV
Higgs Mechanism Supersymmetry
Strong Electroweak Symmetry Breaking
Precision Measurements at lower
energies
Selected Physics Topics
cross sections few fb to few pb ? e.g.
O(10,000) HZ/yr
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Physics Examples
Electroweak Symmetry Breaking - Higgs
mechanism - no Higgs scenarios
Supersymmetry - unification of
forces - dark matter Precision tests
of the Standard Model - top
quark properties - high luminosity
running at the Z-pole
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The Higgs Key to Understanding Mass
Dominant production processes at ILC
Task at the ILC - determine properties of the
Higgs-boson - establish Higgs mechanism
responsible for the origin of mass . . .
together with LHC
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Tasks at the ILC

• Establishing the Higgs mechanism as being
  responsible forEW symmetry breaking requires
  more than discovering oneor more Higgs bosons
  and measuring its/their mass(es).
• Precision measurements must comprise
• Mass
• Total width
• Quantum numbers JCP (Spin, CP even?)
• Higgs-fermion couplings (? mass?)
• Higgs-gauge-boson couplings (W/Z masses)
• Higgs self-coupling (spontaneous symmetry
  breaking)
• Precision should be sufficient to distinguish
  between
• different models (e. g. SM/MSSM, effects from XD,
  ...)

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The Higgs Key to Understanding Mass
Recoil mass spectrum ee -gt HZ with Z -gt ll-
Ds 3
model independent measurement
Dm 50 MeV
sub-permille precision
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ee -gt HZ Z -gt l l H -gt
qq
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Precision physics of Higgs bosons
ee -gt HZ diff. decay channels
mH 120 GeV
DmH 40 MeV
mH 150 GeV
DmH 70 MeV
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The Higgs Key to Understanding Mass
Higgs branching ratios
?BR/BR bb 2.4 cc 8.3 gg 5.5 tt 6.0 gg 23
.0 WW 5.4 For 500 fb-1 MH 120 GeV
Model-independent measurements at -level possible
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Example Top Yukawa Coupling
LHC sensitive to top Yukawa coupling of light
Higgs through tth production. ILC BR measurement
(h?bb and h?WW) turns rate measurement into an
absolute coupling measurement ILC direct
measurement only at high energy (gt 800 GeV)
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The Higgs Key to Understanding Mass
Higgs self coupling
gHHH
F(H)?v2H2 ?vH3 1/4?H4 SM gHHH 6?v, fixed
by MH
??/? 10-20 for 1 ab-1
requires excellent calorimeter resolution
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The Higgs Key to Understanding Mass
Testing the Yukawa couplings
Precision level
through the measurement of absolute BRs
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e.g. Coupling Precision and New Physics
Yamashita
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Heavy SUSY-Higgs
Heavy SUSY Higgs bosonsobservation and
mass/BR/width(?) measurements
deep into the LHC wedge
region at 800-1000 GeV LC
HA 5s discovery possible up to Sm
vs 30 GeV
HA? bbbb and HA ? bbtt/ttbb observable
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Precision physics of Higgs bosons
Conclusion
precision measurements at the ILC together with
the results from LHC are crucial to establish
the Higgs mechanism responsible for the origin of
mass and for revealing the character of the Higgs
boson if the electroweak symmetry is broken in
a more complicated way then foreseen in the
Standard Model the LC measurements strongly
constrain the alternative model
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Beyond the Higgs
Why are electroweak scale (102 GeV) and the
Planck scale (1019 GeV) so disparate ? Are
there new particles ? ? supersymmetry
new forces ? ? strong interactions
hidden dimensions ?
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Supersymmetry
Introduction of an additional symmetry to the SM
boson ? fermion symmetry Each SM particle gets a
SUSYpartner whose spin differs by1/2. All other
quantum numbersare equal. But so far no SUSY
particle seen (SUSY symmetry broken)
but SUSY well motivated theory ?
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Solution to hierarchy problem
Motivation 1 It solves the hierarchy problem
The divergence in the Higgs mass corrections is
cancelledexactly for unbroken SUSY. If it is not
broken too strongly (i. e. if the SUSY partners
areat lt 1 TeV), there is no fine tuning
necessary.
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Unification of gauge couplings
Motivation 2 Gauge coupling constants unify
Minimal supersymmetric SM
(Requires light (lt TeV) partnersof EW gauge
bosons)
This is achieved for sin2qWSUSY
0.2335(17) Experiment sin2qWexp 0.2315(2)
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More good reasons ...
Motivation 3 Provides cold dark matter
candidate If lightest SUSY particle is stable, it
is an excellentdark matter candidate Motivation
4 Link to gravity SUSY offers the theoretical
link to incorporate gravity.Most string models
are supersymmetric. Motivation 5 Predicts light
Higgs boson SUSY predicts a light (lt 135 GeV)
Higgs boson as favoredby EW precision data.
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Supersymmetry
? best motivated extension of SM grand
unification connection to gravity light Higgs
sin2TW dark matter candidate . ?
mass spectrum depends on the unknown breaking
scheme ? LC task for SUSY reconstruction of
kinematically accessible sparticle spectrum
i.e. measure sparticle properties (masses,
Xsections, spin-parity) extract
fundamental parameters (mass parameters, mixings,
couplings) at the weak scale
extrapolate to GUT scale using RGEs ?
determine underlying supersymmetric model
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Supersymmetry
Mass spectra depend on choice of models and
parameters...
well measureable at LHC
precise spectroscopy at the Linear Collider
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Production and decay of supersymmetric
particles at ee- colliders (ILC)
Supersymmetry
charginos
s-muons
Lightest supersymmetric particle stable in most
models candidate for dark
matter
Experimental signature missing energy
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Supersymmetry
Measurement of sparticle masses
ex Charginos threshold scan
ex Sleptons lepton energy spectrum
in continuum
achievable accuracy
dm/m 10-3
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Test of Unification
MSSM 105 parameters some from LHC, some from
ILC
Extrapolation of SUSY parameters from weak to GUT
scale (e.g. within mSUGRA) Gauge couplings unify
at high energies, Gaugino masses unify at same
scale Precision provided by ILC for sleptons,
charginos and neutralinos will allow to test if
masses unify at same scale as forces
Gluino (LHC)
SUSY partners of electroweak bosons and Higgs
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Sparticles may not be very light
BUT
? Second lightest visible sparticle
Lightest visible sparticle ?
JE Olive Santoso Spanos
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LSP light in most cases
BUT
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Aaaaaaaaaaaaaaaa
Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Aaaaaaaaaaaaaaaa
? Second lightest visible sparticle
1000
Lightest visible sparticle ?
Lightest visible sparticle ?
1000
Lightest invisible sparticle ?
Lightest invisible sparticle ?
Kalinowski
Kalinowski
ee- ??1?2
Lightest visible sparticle ?
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MSSM parameters from global fit
LHC and ILC
? only possible with information from BOTH
colliders
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Dark Matter
If SUSY LSP responsible for Cold Dark Matter,
need acceleratorsto show that its properties are
consistent with CMB data - Future precision on
?h2 2 (Planck) gt match this precision! - WMAP
points to certain difficult regions in parameter
space
small
e.g. smuon pair production at 1TeVonly two very
soft muons! need to fight backgrounds
Battaglia
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LSP responsible for relic density OCDM ?
Bourjaily,Kane, hep-ph/0501262
? need to measure many parameters, in particular
coupling to matter
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Dark Matter and SUSY

• - is Dark Matter linked to the LSP?

a match between collider and astrophysical
measurements would provide overwhelming evidence
that the observed particle(s) is dark matter
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Comparison with expectations from direct searches
constrain mass and interaction strength
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Conclusions
Supersymmetry
The Linear Collider will be a unique tool for
high precision measurements ? model independent
determination of SUSY parameters ? determination
of SUSY breaking mechanism ? extrapolation to
GUT scale possible
but what if
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No Higgs boson(s) found.

• divergent WL WL ? WL WL amplitude in SM at
• SM becomes inconsistent unless a new strong
  QCD-like interaction sets on
• Goldstone bosons (Pions) W states
  (technicolor)
• no calculable theory until today in agreement
  with precision data
• Experimental consequences deviations in
  
• triple gauge couplings
  quartic gauge couplings

LC (800 GeV) sensitivity to energy scale
? triple gauge couplings 8 TeV quartic gauge
couplings 3 TeV ? complete threshold
region covered
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Extra dimensions

• Completely alternative approach to solve
  hierarchy problemThere is no hierarchy
  problem
• Suppose the SM fields live in normal 31 dim.
  space
• Gravity lives in 4 d dimensions
• d extra dimensions are curled to a small volume
  (radius R)

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Extra Dimensions
classical
GN1/MPl2
ADD-model d new space dimension with radius R,
which only communicates through gravity
rgtgtR
compare 4-dim and 4d ?V(r)
example MD 1 TeV for d 2(3) ? R 1 mm(nm)
potentially macroscopic size! Detectable?
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Extra dimensions
For r lt R, gravity follows Newton's law in 4 d
dimensions
For r gt R, gravity follows effectively Newton's
law in4 dimensions, since the distance in the
extra dimensionsdoes not rise anymore
The Planck mass
only effectively appearsso high at large
distances. The true scale of gravity is
If e. g. R O(100 mm) and d 2, one obtains ?
Gravity might become visible at TeV-scale
colliders!
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Extra dimensions
Extra dimensions provide an explanation for the
hierarchy problem
String theory motivates brane models in which our
world is confined to a membrane embedded in a
higher dimensional space
e.g. large extra dimensions Emission of
gravitons into extra dimensions Experimental
signature single photons
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Extra dimensions
cross section for anomalous single photon
production
d of extra dimensions
measurement of cross sections at different
energies allows to determine number and scale of
extra dimensions (500 fb-1 at 500 GeV, 1000 fb-1
at 800 GeV)
ee- -gt gG
Energy
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Extra dimensions
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Precision measurementsof SM processes
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Precision electroweak tests
LEP,SLD, Tevatron
the top-quark is playing a key role in precision
tests.. remember the indirect determination of
the mass of the Higgs
??top
indirect
direct
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Precision electroweak tests
As the heaviest quark, the top-quark could play a
key role in the understanding of flavour
physics..
requires precise determination of its
properties.
Energy scan of top-quark threshold
?Mtop 100 MeV
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Precision electroweak tests
mSUGRA
dM(top) 2 GeV
dM(top) 0.1 GeV
Heinemeyer et al, hep-ph/0306181
? constrain allowed parameter space
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Precision Electroweak Tests
? high luminosity running at the Z-pole Giga Z
(109 Z/year) 1000 x LEP in 3 months
with e- and e polarisation
?sinTW 0.000013
together with ?MW 7 MeV (threshold
scan) and ?Mtop 100 MeV
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The ILC physics case
0. Top quark at threshold 1. Light Higgs
(consistent with precision EW) ? verify
the Higgs mechanism is at work in all
elements 2. Heavy Higgs (inconsistent with
precision EW) ? verify the Higgs mechanism
is at work in all elements ? find out why
prec. EW data are inconsistent 3. 1./2. new
states (SUSY, XD, little H, Z, ) ?
precise spectroscopy of the new states ?
precision measurements of couplings of SMnew
states properties of new particles above
kinematic limit 4. No Higgs, no new states
(inconsistent with precision EW) ? find
out why precision EW data are inconsistent
? look for threshold effects of strong/delayed
EWSB Early LHC data likely to guide the
direction ? choice of ILC options LHC ILC data
analysed together ? synergy!
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Intermezzo ILC Physics Reach
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The power of an Electron-Positron Linear Collider
options e-e-, e?, ??
ILC Machine for Discoveries and
Precision Measurements
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e? and ?? options
P.Zerwas, PLC05
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e? and ?? options
P.Zerwas, PLC05
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e? and ?? options
P.Zerwas, PLC05
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e? and ?? options
P.Zerwas, PLC05
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e? and ?? options
V.Telnov, PLC05
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e? and ?? options
P.Zerwas, PLC05
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e? and ?? options
P.Zerwas, PLC05
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ILC/XFEL Synergy
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ILC - XFEL Synergy
XFEL X-ray free-electron laser In the XFEL,
electrons are first accelerated to high energies
(some 20 GeV) using superconducting TESLA
cavities like the ones planned for ILC then made
to emit high-intensity X-ray laser flashes
passing through undulators XFEL opens up new
possibilities for experimentation, e.g.
film chemical reactions map the
atomic details of molecules capture
three-dimensional images of the objects. The
XFEL is being planned as a European project with
a strong connection to the DESY.
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Project Timelines
2006
2007
2008
2015
2010
2012
2005
construction
commissioning
ILC
Technically driven schedule
physics
preparation
construction
EURO XFEL
operation
EUROTeV
CARE
UK LC-ABD
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Location of the European XFEL
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The TESLA Test Facility / VUV-FEL / FLASH
RF gun
M2
M3
M4
M5
M6
M7
M1
undulators
bunch compressor
bunch compressor
collimator
FEL experimental area
bypass
Laser
1000 MeV
4 MeV
150 MeV
450 MeV
Beam time for FEL experiments AND FEL
and ILC related RD
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ILC - XFEL Synergy
Some examples of ongoing work for the XFEL at
DESY (approved project) relevant to ILC -
Qualification of vendors in all regions (Europe,
US and Asia) - Industrial studies prototypes
for klystrons - Involve industry in string
module assembly 3 industrial studies -
Industrial studies for RF coupler fabrication -
Further experience with cavity treatment, improve
statistics for cavities - Build up module test
stand ? end of 2005. Further Synergy by
operating FLASH, XFEL commissioning etc
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Preparation of TESLA Cavities

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Summary
The scientific case for a Linear Collider is
strong and convincing, a world consensus
exists on its importance and on its timing
w.r.t. the LHC ILC and LHC offer a
complementary view of Nature at the energy
frontier Detector technologies to do the
physics at the ILC are being developed The
SC technology for the ILC is well developed
2015 is the target date for commissioning. To
reach this we have to keep going at full
speed. At present, community is keeping timeline.
. . Politicians are following the process
(technical decision, joint global design,
self-organisation,..)
The ILC provides an exciting and promising future
for discoveries and for understanding the
universe and its origin