Introduction to the ILC

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Introduction to the ILC

• Contents
• - Introduction
• - Why LC
• - Whats ILC
• Technical Challenge

Fumihiko Takasaki KEK May 20, 2006
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Basic Units and Numbers

• Units of Energy Electron Volt
• MeV Mega Electron Volt 106 eV
• GeV Giga Electron Volt 109 eV
• TeV Tera Electron Volt 1012 eV
• Particle Masses Electron 0.5 MeV, Proton
  938 MeV
• Cross section s
• nb 10-33 cm2 , pb 10-36 cm2 , fb
  10-39cm2
• Luminosity L
• Number of Particle collisions per unit time
  per unit area
• e.g. the KEKB recorded L 1.6 x1034
  cm-2sec-1
• Number of event per unit time, N N s x L
• Integrated Luminosity ?L
• Luminosity integrated over some time
  interval,
• e.g. the KEKB recorded ?L 1039cm-2
  fb-1 in a day.

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Notice
Although this is a lecture on the ILC, the
International Linear Collider, I am spending
some time for the comparison between the
ILC, an electron-positron collider, and the
LHC, a proton-proton collider which is under
construction near Geneve, Switzerland, because
they aim at the same physics goals.
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Introduction
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• Since ancient days, human being has pursued to
• understand natural phenomena,
• especially,
• what is matter made of
• how matter behaves.
• In modern times, the Particle Accelerators have
• revealed the secrets of matters and brought the
• Sub-atomic World to our eyes.
• And human being has arrived at the concept of
• the Standard Model of Particles.

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Standard Model of Particles
Kobayashi, Maskawa
Neutrino mixing
Glashow, Salam, Weinberg
T-quark
Higgs, Nambu
W/Z boson
Gell-Man
B-meson
Feynman, Schwinger, Tomonaga
t-lepton
D-meson
Lee, Yang
m-Neutrino
Yukawa
Kaon
Dirac
Pion
Muon
Schroedinger
Positron
Neutron
Einstein
Proton
Great Theories
Electron
Maxwell
Hewton
Great Discoveries
Galilei
by particle accelerators
Aristotle
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In the Standard Model, there are three families
of quarks and leptons together with four kinds
of force mediators .
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• To complete the Standard Model, we need to go a
  step further. There is one missing member of the
  Standard Model,
• Higgs Particle, the Higgs.
• The Standard Model requires its existence !!
• Where is the Higgs?
• How it looks like ?
• The Standard Model tells us its properties
  except for its mass. However, recent studies
  have narrowed down its possible mass range
• 114 200 GeV.

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Mass Range of the Higgs
The current knowledge of Mass Range of The Higgs
comes from the examination of very precise
experimental data collected in the last decades
incorporating the Higher Order effects of the
interactions.
Higher Order Correction
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Estimation of the Higgs mass range
11
Notice

• Higgs fields, introduced by Higgs in 1963,
  was successfully incorporated in an attempt to
  unify the electromagnetic force and weak force by
  Glashow, Salam and Weinberg in the late 1960s,
  Glashow-Salam-Weinberg theory.
• This theory is supported by experimental
  discoveries such as
• the weak neutral current
• the W and Z boson with their masses
• and interaction properties consistent
• with the prediction.

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Why LC
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One of the motivations is to find and to fully
understand the Higgs Particle.
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It should be mentioned that a proton-proton
collider, the Large Hadron Collider, the LHC, is
under construction at CERN in Europe with the
expense of about 4 B Euro. Its main motivation
is also to find and understand the Higgs. The
Higgs will be discovered either at the Tevatron,
a proton-anti-proton collider at FNAL in US,
tomorrow, or, at the LHC soon after it becomes
operational. However, even if it is discovered
at the Tevatron or at the LHC, the ILC will be
needed to study its properties in detail. This
detailed study of the Higgs will open the window
for the world beyond the Standard Model.
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LHC
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Discovery Potential of the Higgs
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Physics cases with the ILC
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How do you know you have discovered the Higgs ?
Measure the quantum numbers. The Higgs must have
spin zero !
The ILC will measure the spin of any Higgs it can
produce by measuring the energy dependence of the
production cross section from threshold
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The ILC measures the coupling strength of the
Higgs with other particles.
Coupling-mass relation
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What can we learn from the Higgs?
Precision measurements of Higgs coupling can
reveal extra dimensions in nature

• Straight blue line gives the standard model
  predictions.
• Range of predictions in models with extra
  dimensions -- yellow band, (at most 30 below the
  Standard Model)
• The red error bars indicate the level of
  precision attainable at the ILC for each particle

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Direct production from extra dimensions ?
New space-time dimensions can be mapped by
studying the emission of gravitons into the extra
dimensions, together with a photon or jets
emitted into the normal dimensions.
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Finding the Higgs is not the end of the story.
The Standard Model can not give answers
to mysteries such as

• Why particle masses are so different?
• Why there are only three generations ?
• Are all forces unified?
• How can the recent findings in the
• Universe understood?

We need to go beyond the Standard Model.
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Recent findings in the Universe.

• Dark Matter is seen in galaxies and seems
  needed to cluster galaxies in the early universe.
  It seems to be a particle (or particles) left
  over from the Big Bang. Physics beyond the
  Standard Model gives natural candidates.
• Dark Energy is driving the universe apart it
  may be due to a spin 0 field, so study of the
  Higgs boson may help to understand it.

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Is there a New Symmetry in Nature?
Super-symmetry
Bosons
Fermions
Integer Spin 0, 1,..
Half integer Spin 1/2, 3/2,..

• The Super-symmetry may give answers if
• Forces are unified,
• Why particle masses are so small compared
• with the Planck Mass,
• Naturally, the Super-symmetric particles can be
  candidates of Dark Matter,

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Super-Symmetry
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The ILC, together with the LHC, will play a key
role in exploring the world beyond the Standard
Model.
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Comparison between the ILC and LHC
ILC LHC
Beam Particle Electron x Positron
Proton x Proton
CMS Energy 0.5 1 TeV
14 TeV
Luminosity Goal 2 x 1034 /cm2/sec
1 x1034 /cm2/sec
Accelerator Type Linear
Circular Storage Rings
Technology Supercond. RF
Supercond. Magnet
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Comparison between the ILC and LHC -- continued
ILC LHC
s total 5 x 10-36 cm2 _at_ 500 GeV
1010 x10-36 cm2
s (Annihilation )
s (Inelastic)
Typical s Higgs Prod 0.05 x 10-36 cm2
0.07 x10-36 cm2
s (ee ? ZH)
s (pp ? H X) Br(H ? gg)
Experimental CMS energy fixed
Reaction Energy features
uncontrollable
Experimental Smaller background Huge
Backgrounds features
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Beam Energy (Eb) vs Reaction Energy (Ereact)
a
b
In the case of high energy electron-positron
annihilation, 2Eb Ereact. And therefore,
the collision energy is fully converted to create
new states.
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However, in the case of high energy
proton- proton collision, 2Eb gtgt Ereact and
Ereact can not be controlled.
Gluon-Gluon Collision
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Typical event pattern for the Higgs particle
LHC
ILC
e e ? Z H Z ? e e, H ? b
b
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ILC Higgs signal
LHC Higgs signal
500fb-1
H? ??
Typical numbers Tagging efficiency 30-50
S/N gt 1
ILC(ee-?HZ production)
ttH?WbWbbb?lnjjbbbb
ATLAS
30fb-1
Bkg.
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The ILC is to look at some objects with well
focused glasses.
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What is the ILC
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The International Linear Collider (ILC)
It is a project designed to smash together
electrons and positrons at the center of mass
energy of 0.5 TeV initially and 1 TeV later.
The ILC Global Design Effort team, established
in 2005, has been making its accelerator design.
Recently, it worked out the baseline
configuration for the 30-km-long 500 GeV collider.
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One comment on Linear vs circular electron-positro
n collider
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Cost Advantage of Linear Colliders

• Synchrotron radiation
• DE (E4 /m4 R)

m,E
R

• Therefore
• Cost (circular) a R b DE a R b
  (E4 /m4 R)

• Optimization R E2 ? Cost c E2

• Cost (linear) a? L, where L E

Circular Collider
cost
Linear Collider
Energy
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Luminosity and Beam size
n1 x n2
Luminosity L f
4p sx sy
f Collision frequency of the beams
n1, n2 Number of particles in the beam
bunch sx, sy Beam size parameter in x and y
direction
For example, to get L 1034/cm2/sec with
parameters f 5x3000/sec , n1 n2
2x1010 , sx 100 x sy 1034
1.5x104x4x1020/4/3.14/100/sy2
48 x 1020/sy2 sy
6.9x10-7 cm 6.9 nm
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Scheme of Linear Collider
5 nano m
Interaction Point (IP)
Squeeze the beam as small as possible for High
luminosity
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Parameters for the ILC

• Ecm adjustable from 200 500 GeV
• Luminosity ? ?Ldt 500 fb-1 in 4 years
• Ability to scan between 200 and 500 GeV
• Energy stability and precision below 0.1
• Electron polarization of at least 80
• The machine must be upgradeable to 1 TeV

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ILC Baseline Configuration
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The ILC main components

• Electron source
• To produce electrons, light from a
  titanium-sapphire laser hit a target
• and knock out electrons. The laser emits 2-ns
  "flashes," each creating
• billions of electrons. An electric field "sucks"
  each bunch of particles into
• a 250-meter-long linear accelerator that speeds
  up the particles to 5 GeV.
• Positron source
• To produce positron, electron beam go through
  an undulator. Then,
• photons, produced in an undulator, hit a titanium
  alloy target to generate
• positrons. A 5-GeV accelerator shoots the
  positrons to the first of two
• positron damping rings.
• Damping Ring for electron beam
• In the 6-kilometer-long damping ring, the
  electron bunches traverse a
• wiggler leading to a more uniform, compact
  spatial distribution of particles.
• Each bunch spends roughly 0.2 sec in the ring,
  making about 10,000 turns
• before being kicked out. Exiting the damping
  ring, the bunches are about
• 6 mm long and thinner than a human hair.

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• Damping Ring for positron beam
• To minimize the "electron cloud effects,"
  positron bunches are injected alternately into
  either one of two identical positron damping
  rings with 6-kilometer circumference.
• Mian Linac
• Two main linear accelerators, one for
  electrons and one for positrons, accelerate
  bunches of particlesup to 250 GeV with 8000
  superconducting cavities nestled within
  cryomodules. The modules use liquid helium to
  cool the cavities to - 2K. Two 12-km-long tunnel
  segments, about 100 meters below ground, house
  the two accelerators. An adjacent tunnel provides
  space for support instrumentation, allowing for
  the maintenance of equipment while the
  accelerator is running. Superconducting RF system
  accelerate electrons and positrons up to 250 GeV.
• Beam Delivery System
• Traveling toward each other, electron and
  positron bunches collide at 500 GeV. The baseline
  configuration of the ILC provides for two
  collision points, offering space for two
  detectors.

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Linear Collider Facility
Particle Detector
Main Research Center
30 km long straight tunnel and accelerators
inside
Two tunnels, one for the accelerator units and
the other for the devices to provide RF
power the accelerator units.
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A facility on the surface to provide access to
the tunnel and to provide He gas, electricity,
cooling water, .
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Technical Challenges
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Technical Challenges at the ILC
Superconducting RF Acceleration technology
- Nano-meter size beam handling technology
Laser wire system
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Acceleration
Electric Field
Electron (positron)
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Cryomodule to be fabricated at KEK this year
with four 9 cell cavities
13 m
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An example of a 9-cell cavity performance.
ILC Specification
Gradient

• Enormous RD efforts have been made world wide
  to
• establish the superconducting RF
  acceleration technology.
• We need more than 10,000 units of this kind of
  cavity
• assembled in the cryomodule.

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It seems that we have technology in hand to
squeeze beam down to the required size.
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ATF
Accelerator Test Facility
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It is needed to establish technology for the beam
handling of with very small emittance.
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World-wide Strong cooperation for linear
collider accelerator RD
EU
US
Asia
2003? 7?
Competition for hosting the linear collider
facility
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GDE Organization
GDE Directorate
GDE Executive Committee
GDE R D Board
GDE Change Control Board
GDE Design Cost Board
Global RD Program
RDR Design Matrix
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Cost of the ILC
The GDE is now trying to make an estimation of
the ILC construction (and operation ?) cost. It
will be included in the Reference design Report,
which will be worked out by the end of this year.
As for your information, let me quote the LC
cost estimated for the 500 GeV TESLA project,
which was 3.1B (4B) (not including salaries).
Some colleagues in US tried to translate it to
the US way of estimation, which turned out 8B.
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Cost Breakdown by Subsystem
Civil
SCRF Linac
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Physics and Detectors WWS Worldwide Study
on Physics and Detectors
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Worldwide Study Group

• Started in 1998 (Vancouver ICHEP)
• 6 committee members from each of 3 regions
• 3 co-chairs - now members of GDE
• J. Brau
• F. Richard
• H. Yamamoto
• Tasks (in short)
• Recognize and coordinate detector concept studies
• Register and coordinate detector RDs
• Interface with GDE
• Organize LCWS (1 per year now)

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Physics and Detector Study Groups
SiD Silicon Detector LDC Large Detector
Concept GLD Global Large Detector
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International Linear Collider Timeline
2005 2006 2007 2008
2009 2010
Global Design Effort
Project
Baseline configuration
Reference Design
Technical Design
ILC RD Program
Expression of Interest to Host
International Mgmt
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Conclusions

• The ILC will deepen our understanding on the
  subatomic world and also on the Universe.
• The world community has been spending enormous
  efforts for the realization of the ILC. Under
  the leadership of the GDE, the design of the ILC
  is in progress in a remarkable speed.
• We hope that we can realize our dream soon
  to construct the ILC by a real international
  collaboration.
• Let me thank those who helped me to make this
  slides.

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Back-up slides
64
Electron Positron Collider VS Hadron Collider
? History tells us The hadron-collider is a
machine for a particle discovery. The
electron-collider is essential for detailed
studies of discovered particles and to reveal the
new physics.
Discovery Detailed Studies Charm
quark BNL / SPEAR SPEAR
Tau lepton SPEAR
SPEAR Bottom quark FNAL
Cornell W/Z boson SPPS
LEP and SLC Top quark
FNAL ILC ??? Higgs
particle LHC ??? ILC
???
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Positron Source
Helical Undulator Based Positron Source with Keep
Alive System
Keep Alive This source would have all bunches
filled to 10 of nominal intensity.
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Beam Delivery System
Electron Source
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Improvement Record of Acceleration Gradient for
the Superconducting RF cavity
Single cell
ILC Parameter 31.5 MV
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GDE RDR / RD Organization
FALC
ICFA
FALC Resource Board
ILCSC
GDE Directorate
GDE Executive Committee
GDE R D Board
GDE Change Control Board
GDE Design Cost Board
Global RD Program
RDR Design Matrix
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Scientific Justification for the ILC

• The ILC will be very expensive and thus the
  scientific justification must be very strong.
• The detailed study of the Higgs is not the only
  physics case. There are plenty of cases for
  example, study of mysteriously heavy top quark,
  study of Super-symmetric particles if it exists,
  search for hints of new space-time dimension,
  finding dark matter, indications of force
  unification.
• The justification for the ILC must be made in
  the context of the LHC. The LHC will make the
  first explorations of the new energy regime the
  role of the ILC is to provide the detailed maps
  to tell us what the new physics is and what it
  means.

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Electron beam
Positron beam
1.
Accelerate in 30 km straight (linear) tunnel
2.
Collide beams
5 nano m
3.
Detect reaction by precise detector
4.
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