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Future Colliders:Opening Windows on the World
Young-Kee KimThe University of Chicago
ICFA SeminarSeptember 28 - October 1, 2005
Kyungpook National University, Daegu, Korea
Welcome to Korea
Calligraphy by my father
Accelerators are Powerful Microscopes.
They make high energy particle beams that allow us to see small things.
seen byhigh energy beam(better resolution)
seen bylow energy beam
(poorer resolution)
Accelerators are also Time Machines.
E = mc2
They make particles last seen in the earliest moments of the universe.
Energy
Particle and anti-particle annihilate.
particle beam
energy
anti-particle beam
energy
Accelerators powerful tools!
PEP-II, SLAC, Palo Alto, USA
HERA, DESY, Hamburg, Germany
KEKb, KEK, Tsukuba, Japan
Tevatron, Fermilab, Chicago, USA
1929
Ernest Lawrence(1901 - 1958)
3/4 of century later
Tevatron at Fermilabx104 bigger, x106 higher energy
Today
Many generations of Accelerators created with higher and higher energy given to the beam particle
CDF ~1500 Scientists D0
With advances in accelerators, we discovered many surprises.
Our field has been tremendously successful in creating and establishing
“Standard Model of Particle Physics” answering”what the universe is made of” and “how it works”
Energy
Lum
inos
ity(C
ollis
ion
Rat
e)
Time
~90 years ago
110,000
~60 years ago
110
~40 years ago
1100,000
Present
What is the universe made of?
electron
up quarkdown quark
atom
nucleus protonneutron
1100,000
of human hair
Rutherford
Everything is made of electrons, up quarks and down quarks.
Are electrons, up and down quarks the smallest things? Are they made of even smaller things?
top quark
anti-top quark
ZW+, W-
. . . .e e- u d s c b
gluons
Elementary Particles and Masses
e e+ u d s c b- - - - - - - -
(Mass proportional to area shown but all sizes still < 10-19 m)
Why are there so many? Where does mass come from?
Gravitational Force Electromagnetic Force
Issac Newton(1642 - 1727)
James Clerk Maxwell(1831 - 1879)
What holds the world together?Beginnings of Unification
Einstein tried to unify electromagnetism and gravity
but he failed.
Unification of Gravity and Electromagnetism?
radioactive decays
holding proton, nucleus
gluons
Weak Force
Strong Force
Enrico Fermi(1901 - 1954)
1 fm = 10-15 m
Dream of Unification continues!
We believe that there is an underlying simplicitybehind vast phenomena in nature.
Do all the forces become one?At high energy, do forces start to behave the same
as if there is just one force, not several forces?
Extra hidden dimensions in space?
Particle Physics & Cosmology Questions from Astrophysical Observations
Everything is made of electrons, up quarks and down quarks.
Galaxies are held together by mass far bigger (x5) than all stars combined.
Dark Matter - What is it?
Everything that we can see
particlesanti-particles
particles
Accelerators
Where did all antimatter go?
BigBang
Inflation
Create particles & antiparticles that existed ~0.001 ns after Big Bang
E = mc2
Matter and Anti-Matter Asymmetry (CP Violation)
Belle at KEK in Japan and BaBar at SLAC in USdiscovered CP violation in the B system.
From their subsequent precision measurements of CP violation we know now that there must be new physics with CP violation in order to explain matter and anti-matter asymmetry in the universe.
Belle BaBar
Not only is the Universe expanding, it is
Accelerating!!
Where does energy come from?Dark Energy
What is the world made of?What holds the world together?
Where did we come from?
Primitive Thinker
1. Are there undiscovered principles of nature: New symmetries, new physical laws?2. How can we solve the mystery of dark energy?3. Are there extra dimensions of space?4. Do all the forces become one?5. Why are there so many kinds of particles?6. What is dark matter? How can we make it in the laboratory?7. What are neutrinos telling us?8. How did the universe come to be?9. What happened to the antimatter?
Evolved Thinker
From “Quantum Universe”
Answering the Questionswith Next Generation of Accelerators (Colliders)
e+e-
e-proton
proton-proton
today1970 1980 1990 2000 2010 2020 2030
LHC
ILC
TEVATRON
HERA
LEP,SLC
PEP-II, KEKB
VEPP, CLEO-c, BEPC
DANE
FNAL, CERN, J-PARC
Energy Frontier Colliders:
Flavor Specific Accelerators:
e+e- (b factory)
e+e- (c factory)
e+e- (s factory)
CLIC
Collider
LHCb
xx
x
xxx
x
xx xxx
x
Electron
Z,W Boson
Top Quark
Origin of Mass:There might be something (new particle?!) in the universe
that gives mass to particles
Nothing in the universe Something in the universe
Higgs Particles:Higgs Particles:
Coupling strength to HiggsCoupling strength to Higgsis proportional to massis proportional to mass
Mtop (GeV)
W
Z
W, Z
top
bottom
top
top
Higgs
Tevatron: Improve Higgs Mass Pred. via Quantum Corrections
Tevatron Run II
Current precision measurementsfavor light Higgs: < ~200 GeV.
MW
(GeV
)
Tevatron: Improve Higgs Mass Pred. via Quantum Corrections
Mtop (GeV)
MW
(GeV
)
LHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 GeV
M (GeV)
130 GeV HiggsL = 100 fb-1
# of
eve
nts
/ 0.
5 G
eV
Tevatron: Improve Higgs Mass Pred. via Quantum CorrectionsLHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 GeV
MHiggs (GeV)5
Dis
cove
ry L
umin
osity
(fb
-1)
Mtop (GeV)
MW
(GeV
)
Tevatron: Improve Higgs Mass Pred. via Quantum CorrectionsLHC: Designed to discover Higgs with Mhiggs = 100 ~ 800 GeV
Will the Tevatron’s prediction agree with what LHC sees?
5 D
isco
very
/ L
umin
osity
(fb
-1)
MHiggs (GeV)5
Dis
cove
ry L
umin
osity
(fb
-1)
easy
hard
Mtop (GeV)
MW
(GeV
)
115 GeV Higgs is an interesting case!LEP Saw a 2hint
Tevatron 2007
(2.5 fb-1 / expt)95% CL Limit
Tevatron 2009
(8 fb-1 / expt)
WH Wbb
ZH Zbb
75% chance for 3 evidence
10% chance for 5 discovery
LHC
H
ttH ttbb
qqH qq (forward qq jets)
But, Higgs sector may be very complex. New physics models expect multiple Higgs particles.
Higgs
WZ
WZ
d
u
e+
e-
Higgs
Z
Z
LEP
Tevatron
LHC
Supersymmetric Extension of Standard Model (SUSY)
e+ e-
superparticle
e e~
e
spin 1/2 spin 0 Me ≠ Me
Symmetry betweenfermions (matter) and bosons (forces)
“Undiscovered new symmetry”
SUSY solves SM problems: e.g. divergence of Higgs mass, unification.SUSY provides a candidate particle for Dark Matter, solution to matter-
antimatter asymmetry, possible connection to Dark Energy?
If msuper particle < ~1 TeV,fermion and boson loops cancel and Higgs mass becomes stable.
particle super particleHiggs Mass:
~
Higgs in Minimal Supersymmetric Extension of Standard Model
tan
MA (GeV)Mtop (GeV)
MSSM
MW
(GeV
)
TevatronLHCILC
LHC
LHC will be the best place to discover Higgs particles!
If we discover a “Higgs-like” particle,is it alone responsible for giving mass to W, Z, fermions?
Experimenters must precisely measurethe properties of the Higgs particle
without invoking theoretical assumptions.
proton proton (anti-proton!)
e- e+
• elementary particles• well-defined energy and angular momentum• uses its full energy• can capture nearly full information
LHC:
ILC:
ILC can observe Higgs no matter how it decays!
100 120 140 160Recoil Mass (GeV)
MHiggs = 120 GeV
Num
ber
of E
vent
s /
1.5
GeV
Only possible at the ILC
ILC simulation for e+e- Z + Higgswith Z 2 b’s, and Higgs invisible
Cou
plin
g S
tren
gth
to H
iggs
Par
ticle
Mass (GeV)
Standard Model Coupling∞ particle mass
ILC experiments will have the unique ability to make model-independent tests of Higgs couplings
to other particles, at the percent level of accuracy
Standard Model Coupling∞ particle mass
LEP e+e- collider
Coupling Strength to Z boson
e : 0.1%: 0.1%: 0.1% : 0.2%q : 0.1%
(PDG values)
This sensitivity is sufficient to discover extra dimensions, SUSY, sources of CP violation, or other novel phenomena.
The Higgs is Different!
All the matter particles are spin-1/2 fermions.All the force carriers are spin-1 bosons.
Higgs particles are spin-0 bosons.The Higgs is neither matter nor force;
The Higgs is just different.This would be the first fundamental scalar ever discovered.
The Higgs field is thought to fill the entire universe.Could give some handle of dark energy(scalar field)?
Many modern theories predict other scalar particles like the Higgs.Why, after all, should the Higgs be the only one of its kind?Once nature learns how to do something, she does it again!
ILC can search for new scalars with precision.
HIGGS
If discovered,the Higgs is a very powerful probe of new physics.
Hadron collider(s) will discover the Higgs.
ILC will use the Higgsas a window viewing the unknown.
Unification
We want to believe that there was just one force after the Big Bang.
As the universe cooled down, the single force split into the four that we know today.
1TeV = 103GeV(1016K)10-11 s
1016GeV(1029 K)10-38 s
1019GeV(1032K)10-41 s
2.3 x 10-13 GeV(2.7K)
12x109 y
EnergyTempTime
Unification of electromagnetic & weak forces
(electroweak theory)
Long term goal since 60’sWe are getting there.
Beautifully demonstratedat HERA ep Collider at DESY
The main missing link is Higgs boson
HERA
Q2 [GeV2]
Electromagnetic ForceWeak Force
f
HERA:H1 +ZEUS
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Higher energy, Shorter distance
Str
onge
r fo
rce
-1
-1
-1
104 108 1012 1016 1020
Q [GeV]
60
40
20
0
-1
13 orders of magnitude higher energy
The Standard Model fails to unify the strong and electroweak forces.
Adding super-partners
104 108 1012 1016 1020
Q [GeV]
60
40
20
0
-1
-1
-1
-1
With SUSY
But details count!Precision measurements are crucial.
Energy (GeV)
Masses also evolve with energy and matter unifies at high energies.ILC ability in measuring SUSY parameters accurately is crucial to extract mass evolution.
Discovering Matter Unificationin Supersymmetry
Energy (TeV)
Mas
s S
quar
ed
With SUSYUnifying gravity to the other 3 is accomplished by String theory.
String theory predicts extra hidden dimensions in spacebeyond the three we sense daily.
Can we observe or feel them? too small?
Other models predict large extra dimensions:large enough to observe up to multi TeV scale.
Large Extra Dimensions of Space
LHC can discover partner towers up to a given energy scale. ILC can identify the size, shape and # of extra dimensions.
qq,gg GN e+e-,+-
Mee, [GeV]
LHC
Mee [GeV]
DZero
Tevatron
GNq
q
e+
e-
Tevatron Sensitivity2.4 TeV @95% CL
Collision Energy [GeV]
Graviton disappears into the ED
Pro
duc
tion
Rat
e
ILC
GN
e+
e-
Mee [GeV]
Eve
nts
/ 50
GeV
/ 1
00 f
b-1
102
10
1
10-1
10-2
LHC
New forces of nature new gauge boson
LHC has great discovery potential for multi TeV Z’.Using polarized e+, e- beams, and measuring angular distribution of leptons, ILC can measure Z’ couplings to leptons and discriminate the origins of the
new force.
Mee [GeV] M [GeV]
Vec
tor
Cou
plin
g
Axial Coupling
Related to originof masses
Related toorigin of Higgs
Related toExtra dimensions
Tevatron LHC ILC104
103
102
10
1
10-1
Events/2GeV
qq Z’ e+e-
Tevatron sensitivity~1 TeV
CDF Preliminary
Dark Matter
(What is the role of Dark Matter in galaxy formation and shapes?)
a common bond between astronomers, astrophysicists, and particle physicists
Astronomers & astrophysicists over the next two decades using powerful new telescopes will tell us how dark matter has shaped
the stars and galaxies we see in the night sky.
Only particle accelerators can produce dark matter in the laboratory and understand exactly what it is.
The ILC may be a perfect machine to study dark matter.
Dark Matter in the LabUnderground experiments (CDMS) may detect Dark Matter candidates
(WIMPS) from the galactic halo via impact on colliding DM particle on nuclei.
Dark Matter Mass [GeV]
10-4
4
104
3
10-2
4
10 100 1000
Inte
ract
ion
Str
engh
[cm
2 ]
LHC may find DM particles (a SUSY particle) through missing energy analyses.(LHC is the best place to discover many of SUSY particles)
The ILC can determine its properties with extreme detail,allowing to compute
which fraction of the total DM density of the universe it makes.
Dark Matter Mass from Supersymmetry (GeV)F
ract
ion
of D
ark
Mat
ter
Den
sity
Particles Tell Stories!
The discovery of a new particle is often the opening chapter revealing unexpected features of our universe.
Particles are messengers telling a profound story
about nature and laws of nature in microscopic world.
The role of physicists is to find the particles and to listen to their stories.
Discovering a new particle is Exciting!Top quark event recorded early 90’s
We are listening to the story that top quarks are telling us:Story is consistent with our understanding
of the standard model so far. But why is the mass so large?We are now searching for a story we have not heard before.
Mtopworld = 172.7 ± 2.9 GeV
We are hoping in the next ~5 years LHC will discover Higgs. ILC will allow us to listen very carefully to Higgs. This
will open windows for discovering new laws of nature.
Discovering “laws of nature” is even more Exciting!!
This saga continues…. There might be supersymmetric partners, dark matter,
another force carrier, large extra dimensions, …… for other new laws of nature.
Whatever is out there, this is our best opportunity to find it’s story!
Now I want to speak as an experimentalist.
I think this is not only the best opportunitybut also this is a unique opportunity.
If we wait too long, the window of opportunity may close and we will never hear the end of the story.