1. Physics Overview Yasuhiro Okada (KEK)
LCWS 06 & ILC GDE meeting, March 9, 2006
Indian Institute of Science, Bangalore, India

2. Fundamental questions in elementary particle physics
What are the elementary
constituents of matter?
What are forces acting between them?
How has the Universe begun and evolved?

3. How have we come to the Standard Model ?
gravity
general relativity
EM interaction
Electroweak
theory
weak interaction
Fermi theory
Higgs mechanism
strong interaction
nuclear force
pion
quark
QCD
1900
2000

4. Why TeV scale?
This is the scale of the weak interaction, in modern language, the Higgs vacuum expectation value (~246 GeV).
We expect to fine a Higgs boson and “New Physics” associated to the electroweak symmetry breaking.
The answer to the question “what is the physics behind the electroweak symmetry breaking?” is a crucial branching point for the future of particle physics.
Supersymmetry vs.
Low cut-off theory (Little Higgs models, models with large extra-dimension, etc.)

5. Why do we expect physics beyond the Standard Model?
We do not know how the Higgs field arises.
There are evidences which require new particles and/or new interactions.
Neutrino mass
Dark matter
Baryon-anti-baryon asymmetry of the Universe
Expectation of Unification.
GUT, Superstring

6. Why do we need both LHC & ILC?
Two machines have different characters.
Advantage of lepton colliders:
　　e+ and e- are elementary particle　
　　　　(well-defined kinematics).
　　Less background than LHC experiments.
　　Beam polarization, energy scan.
　　g - g, e- g, e- e- options, Z pole option.
LHC
ILC

7. Goals of ILC physics
Higgs physics (Electroweak symmetry breaking and mass generation mechanism of quarks, leptons, and gauge bosons.)
New physics signals
Direct search for new particles and interactions.
Indirect search for new physics effects　　　through the SM particle processes.
Capability of precise measurements of various quantities is a key.

8. Higgs physics
A Higgs boson will be discovered at LHC as long as its properties (production/decay) is similar to the SM Higgs boson.
In order to study the Higgs mechanism at work, Higgs couplings to various particles have to be measured precisely.

9. Higgs boson search at LHC
SM Higgs boson branching ratio
Higgs boson discovery at LHC
MH(GeV) 5

10. Coupling measurements at ILC
(Ecm>700 GeV)
LHC: (10)% for ratios of
coupling constants
ILC: a few % determination
Higgs self-coupling
GLC Project
mH=120 GeV, Ecm= GeV.L=500fb-1

11. New physics effects in Higgs boson couplings
In many new physics models, the Higgs sector is extended and /or involves new interactions. The Higgs boson coupling can have sizable deviation from the SM prediction.
The heavy Higgs boson mass in the MSSM
SUSY correction to Yukawa couplings
B(h->WW)/B(h->tt)
B(h->bb)/B(h->tt) LC
LHC LC
ACFA report
J.Guasch, W.Hollik,S.Penaranda

12. Radion-Higgs mixing in extra-dim model
The triple Higgs coupling in 2HDM
in the electroweak baryogenesis scenario
HEPAP report
Little Higgs model with T parity
S.Kanemura, Y. Okada, E.Senaha
Deviation to 5-10 % level can be
distinguished at ILC
C.-R.Chen, K.Tobe, C.-P. Yuan

13. Direct searches for New Physics
Some type of new signals is expected around 1TeV range, if New Physics is related to a solution of the hierarchy problem. (SUSY, Large extra-dimension, etc )
The first signal of New Physics is likely to be obtained at LHC. (ex. squarks up to 2.5 TeV at LHC)
ILC experiments are necessary to figure out what is New Physics, by measuring spin, quantum numbers, coupling constants of new particles, and finding lower mass particles which may escape detection at LHC.
Beam polarization, energy scan, and well-defined initial kinematics play important roles in ILC studies.

14. SUSY studies at ILC SUSY is a symmetry between fermions and bosons.
Spin determination is essential, ideal for ILC.
W,Z,g, H
gluon
lepton
quark
neutralino,
chargino
gluino
slepton
squark
SM particles
Super partners
Spin 1/2
Spin 0
Spin 1
neutralino mixing
chargino mixing
Mixing angle determination

15. SUSY relation SUSY predicts characteristic relations
among superpartner’s interactions.
Right-handed selectron production
M.M.Nojiri, K.Fujii, and T.Tsukamoto

16. GUT relation If we combine information from
Gaugino mass relation
GUT relation
If we combine information from
LHC and LC, we can test whether
SUSY breaking masses satisfy
GUT and/or Unification conditions
Gauge coupling unification
Scalar mass relation
B.C.Allanach, et al in LHC/LC report

17. Dark matter and collider physics
Energy composition of the Universe
Dark energy 73%
　 Dark matter 23%
　 Baryon　　　　　4%
Dark matter candidate
WIMP （weakly interacting massive particle)
　 a stable, neutral particle
WIMP candidates
Neutralino (SUSY)
KK-photon (UED)
Heavy photon (Little Higgs with T parity)…

18. Cosmological parameter determination WMAP, Planck, …
Dark matter profile
in our galaxy
Thermal history
of the Universe
Cosmological parameter
determination
WMAP, Planck, …
Direct and indirect
(g, e+,anti-p, n ) searches
for dark matter
Thermal relic abundance
Detection rate
Collider search for a dark matter candidate
particle at LHC and ILC.
ILC will play a particularly important role in distinguishing different models
and determine properties of the dark matter candidate.
See, E.A.Baltz,M.Battaglia,M.E.Peskin,and T.Wizansky, hep-ph/

19. SUSY Dark matter at ILC SUSY mass and coupling measurements
=> Identification of dark matter
ALCPG cosmology subgroup

20. Precision measurements of SM processes
Improve precision of the fundamental parameters.
Search for new physics in indirect ways.
The threshold scan improves
the top mass measurement
and determines the top width.
Top quark threshold scan
Deviation of the top width in the Little Higgs model.
GLC report
C.F.Berger,M.Pelestein,F.Petriello

21. Z’ and e+e-->ff processes
Z’ coupling determination at ILC
Even if ILC at 500 GeV cannot produce
a new Z’ particle kinematically,we can
determine left-handed and right-handed
couplings from ee-> ff processes.
This will give important information
to identify the correct theory.
LHC=> mass
ILC => coupling e f Z’
m z’ =2TeV,Ecm=500 GeV, L=1ab-1
with and w/o beam polarization
S.Godfrey, P.Kalyniak, A.Tomkins

22. Conclusions
The LHC experiment is expected to open a new era of the high energy physics by finding a Higgs boson and other new particles.
Establishing the mass generation mechanism is the urgent question. This will be achieved by precise determination of the Higgs couplings, and ILC will play essential roles.
In order to explore New Physics, Higgs coupling measurements, direct study of new particles and new phenomena, and indirect searches through SM processes are all important at ILC.
TeV physics explored at LHC and ILC will lead to new understanding of unification and cosmology.