1 ILC の物理 岡田安弘 (KEK) ILC 測定器学術創成会議 ２００６年６月２８日 KEK.

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ILC の物理

岡田安弘 (KEK)

ILC 測定器学術創成会議２００６年６月２８日　 KEK

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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?

sec10K10

1TeVGeV10cm101216

316

tT

Ed

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How have we come to the Standard Model ?

nuclear force pion quark

gravity

EM interaction

weak interaction

strong interaction

1900 2000

Fermi theory

Electroweak theory

Higgs mechanism

QCD

general relativity

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Why TeV scale?

This is the scale of the weak interaction, in modern language, the Higgs vacuum expectation value (~246 GeV).

We expect to find 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 larg

e extra-dimension, etc.)

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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

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Weak Int. Standard Model

Higgs Physics

EM Interaction

Strong Int.

Gravity

GUTSUSY

Seesaw Neutrino

Superstiring

Alternative scenarios(Extra dim, Little Higgs model,etc)

100 GeV

Dark Matter

Baryogenesis

Inflation

Dark Energy

TeV 1019 GeV

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

LHC ILC

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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.

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[1] 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.

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Higgs boson search at LHC

MH(GeV)

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SM Higgs boson branching ratio Higgs boson discovery at LHC

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Higgs physics at ILC Production of 0(105)Higgs bosons. Determination of spin and parity. Precise mass determination .

Measurements of production corss sections and branching fractions

TESLA TDR

GLC report

Higgs boson couplings to other particles

Mass generation mechanism

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Coupling measurements at ILC

GLC Project

mH=120 GeV, Ecm=300-500 GeV.L=500fb-1

Higgs self-coupling

(Ecm>700 GeV)

LHC: (10)% for ratios of coupling constantsILC: a few % determination

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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.

B(h->bb)/B(h->)

LC

J.Guasch, W.Hollik,S.Penaranda

B(h->WW)/B(h->)

LHC

LC

The heavy Higgs boson mass in the MSSM SUSY correction to Yukawa couplings

ACFA report

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Radion-Higgs mixing in extra-dim model

Little Higgs model with T parity

C.-R.Chen, K.Tobe, C.-P. Yuan

The triple Higgs coupling in 2HDMin the electroweak baryogenesis scenario

HEPAP report

S.Kanemura, Y. Okada, E.Senaha

Deviation to 5-10 % level can be distinguished at ILC

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[2] 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.

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SUSY studies at ILCSUSY is a symmetry between fermions and bosons. Spin determination is essential, ideal for ILC.

W,Z,H

gluon

lepton

quark

neutralino,chargino

gluino )~(g

)~(

slepton

squark )~(q

)~

(l

SM particles Super partners

Spin 1/2 Spin 0

Spin 1 Spin 1/2

Spin 1Spin 1/2

Spin 0

neutralino mixing chargino mixing

Mixing angle determination

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SUSY relation

M.M.Nojiri, K.Fujii, and T.Tsukamoto

Right-handed selectron production

SUSY predicts characteristic relationsamong superpartner’s interactions.

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If we combine information fromLHC and LC, we can test whetherSUSY breaking masses satisfyGUT and/or Unification conditions

Gauge coupling unification

GUT relation

B.C.Allanach, et al in LHC/LC report

Gaugino mass relation

Scalar mass relation

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Large extra-dimensions An alternative solution to the hierarchy

problem. LC physics: Size and numbers of extra-dimensions, The spin 2 property of Kaluza-Klein gr

avitons.

G.W.Wilson

Angular distribution -> Spin 2 exchange

N.Delerue, K.Fujii, N.Okada

graviton

matter

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[3] Dark matter and collider physics Energy composition of the Unive

rse Dark energy 74%　 Dark matter 22%　 Baryon 　　　　　 4% Dark matter candidate WIMP （ weakly interacting mas

sive particle)　 a stable, neutral particle WIMP candidates Neutralino (SUSY) KK-photon (UED) Heavy photon (Little Higgs with

T parity)…

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Cosmological parameterdetermination

WMAP, Planck, …

Direct and indirect (, e+,anti-p, ) searches

for dark matter

Collider search for a dark matter candidateparticle at LHC and ILC.

ILC will play a particularly important role in distinguishing different modelsand determine properties of the dark matter candidate.

Thermal history of the Universe

Dark matter profilein our galaxy

Thermal relic abundance Detection rate

See, E.A.Baltz,M.Battaglia,M.E.Peskin,and T.Wizansky, hep-ph/0602187

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SUSY Dark matter at ILCALCPG cosmology subgroupSUSY mass and coupling measurements

=> Identification of dark matter

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[4] Precision measurements of SM processes Improve precision of the fundamental parameters. Search for new physics in indirect ways.

GLC report

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.

C.F.Berger,M.Pelestein,F.Petriello

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Z’ and e+e-->ff processesEven if ILC at 500 GeV cannot produce a new Z’ particle kinematically,we can determine left-handed and right-handedcouplings from ee-> ff processes.This will give important information to identify the correct theory.

S.Godfrey, P.Kalyniak, A.Tomkins

m z’ =2TeV,Ecm=500 GeV, L=1ab-1

with and w/o beam polarization

e

e

f

f

Z’

LHC=> massILC => coupling

Z’ coupling determination at ILC

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[5] Physics Benchmarks for the ILC DetectorsM.Battaglia, T.Barklow, M.E.Peskin, Y.Okada, S.Yamashita, and P.Zerwas, hep-ex/0603010

The big table

•Benchmark processes for detector design and optimization.•Selected from important physics reactions

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The short list

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Conclusions The LHC experiment is expected to open a new era of th

e 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.