Summary on Physics Session

The 8th ACFA Workshop

July 14, 2005, Daegu, Korea

Nobuchika Okada

(KEK & Grad. Univ. Advanced Studies)

1. Introduction

Why do we need LC?

What can we do with LC?

New physics search! LC < LHC for discovery potential

Precision measurements! LC > LHC

Specify new physics SUSY or Extra-dim model or other?

Precisely measure parameters of new physics: coupling, CPV, ..

properties of new particles: spin, party, CP, ..

Target New physics around 100 GeV – 1 TeV

Do the current experiments and /or observations suggest New Physics

around 100 GeV -1 TeV?

Maybe Yes!

From CMB + SN1a + structure formation

Observations of the present Universe after WMAP

Dark Energy 73 %

(cosmological constant)

Dark Matter 23 %

Baryon 4 %

No dark matter candidates in the SM!

need New Physics

if DM is a thermal relic WIMP dark matter with mass O(100) GeV !

What is the origin of baryon asymmetry in the present universe (BAU)?

need mechanism of Baryogenesis

EW baryogenesis SM cannot produce enough BAU

with CP-phase in CKM-matrix and

New Pysics around EW scale

Are there any well-motivate New Physics models?

What properties of them can be revealed at ILC?

SUSY models

light Higgs boson < 150 GeV

lots of new particles (superpartners)

DM candidates neutralino with mass around 100 GeV

Models with extra-dimensions

Large extra-dim model M* = O(1TeV)

Randall-Sundrum model KK mode mass = O(1TeV)

O(1TeV) to solve gauge hierarchy problem

KK graviton phenomena occurs around 1 TeV

Universal extra-dim model 　 (higher dimensional SM)

DM candidate (LKP) with mass around 100 GeV -1 TeV

KK modes of SM particles around 100GeV – 1 TeV

Extended Higgs sector models

Little Higgs model etc.

dynamical origin of EW symmetry breaking

with T parity DM candidates

heavy particles around 1 TeV

Multi-Higgs doublet models

successful EW baryogenesis

New source of Lepton Flavor Violation (LFV)

variation of Higgs mass and Higgs CP properties etc.

What can we do with ILC in order to reveal these new physics?

2. Talks in Physics Session

SUSY related topics

K. Cheung: Splitting split SUSY and signal at LC (mini-reviews)

R. Godbole: Fermion polarization in sfermion decays

Y.G. Kim: Probing the Majorana nature and CP properties of neutralinos

Lepton flavor violation

S. Kanemura: Search for LFV at ILC

K. Tsumura: Lepton flavor violating decays of Higgs bosons

under the rare tau decay results

There were 12 talks including 4 mini-reviews

Lots of interesting LC studies have been reported

LC and cosmology interface through EW baryogenesis scenario

Y. Okada: Electroweak baryogenesis and LC (mini-review)

Extended Higgs sector models

J. Song: Little Higgs Models (mini-review)

D.W. Jung: Partially composite Two-Higgs-doublet models

Extra-dimensional models

S. Matsumoto: Resonant signatures of Universal Extra Dimension model at LC

S. Raychaudhuri: Hunting resonances in e+e- mu+ mu- at LC

with beamstrahlung and ISR

Probing anomalous coupling

R. Godbole: Probing anomalous VVH couplings at an e+e- collider

Generator development

Y. Yasui: Calculation of the six-fermion production at ILC with Grcft

3. Brief summary on each talks

Splitting split SUSY and signal at LC (mini-review)　

Talk by Kingamn Cheung

Split SUSY scenario ino mass <<sfermion mass

solves SUSY FCNC and CP problems easily

Fine-tuning problem returns but we do not care about it

Still has good features of SUSY model

gauge coupling unification

Dark matter candidate (light neutralino)

light SM-like Higgs boson

Some extensions:

Original split SUSY:

High-mu split SUSY

Low mu split

Bino, Wino, Higgsino

DM

Wino DM

Higgsino DM

Gauge coupling unification is OK

Collider signatures

Neutralino and chargino production and decay

via intermediate sfermions disappear

Production processes

Decay processes

Fermion polarization in sfermion decays

Talk by Rohini Godbole

Polarization of final state f information of coupling

In SUSY model, 3rd generation sfermion is among the lightest

Measurement of tau/top polarization from stau/stop decay

is important to extract the information of L-R sfermion mixing

Example) mSUGRA Bino is likely to be the lightest

AMSB Wino is the lightest

Measurement of tau polarization is the key

How to measure it?

See tau hadronic decay modes

J=0

J=1 Differently depends

on tau polarization

Distribution of R is peaked at R < 0.2, 0.8 < R for

around R =0.5 for

Probing the Majorana nature and CP properties of neutralinos

Talk by Yeong-Gyun Kim

In SUSY model, neutralinos are spin1/2 Majorana particle

To probe the Majorana nature and CP properties of neutrinos

see charge self-conjugate 3 body decay of polarized neutralinos

Neutralino produced in decays are 100% polarized

: neutralino polarization vector

Differential decay distribution

with four kinematic functions with

Charge self-conjugate-ness by Majorana particle

CP and CPT invariance relations among

Marorana nature of the neutralinos can be checked thorough lepton energy distribution lepton angler distribution w.r.t neutralino polarization vector

Results of numerical analysis

Lepton energy distribution Lepton angular distribution

Search for LFV at ILC (mini-review) Talk by Shinya Kanemura

LFV is a clear signal of physics beyond the SM

Many new physics models predict LFV

Search for LFV at ILC

LFV in LC

SUSY model : Direct LFV Yukawa determination via the Higgs boson decays Two Higgs model: LFV in a deep inelastic scattering process at a fixed target experiment Two Higgs model:

Tau associated LFV processes may be interesting at ILC

less constrained

Yukawa coupling is large Higgs mediated process is involved

Decoupling property of LFV for gauge and Higgs mediated processes

are deferent gauge

Higgs

Higgs mediated processes are not necessarily decoupled

even in the case of decoupling SUSY mass

Higgs mediated processes become important !

CTEQ6L

• Each sub-process e q (μq) →τq

is proportional to the down-type quark masses.

• For the energy > 60 GeV, the total cross section is enhanced due to the b-quark sub-process

E ＝ 50 GeV 10^(-5)fb 100 GeV 　 10^(-4)fb

250 GeV 　 10^(-3)fb

μ （e） τ

N

qq

h, H, A

X

Proposal of fixed target option

Cross section in SUSY model

Lepton flavor violating decays of Higgs bosons under the rare tau decay results Talk by Koji Tsumura

LFV via Higgs decay in two Higgs doublet model

Extended Higgs sector violates lepton flavor

LFV decay of the lightest Higgs boson at ILC

Tau associated process is important large Yukawa

Less constraint from tau rare decay

LFV Higgs boson decay v.s. constraint from rare tau decay

Excluded by tau rare decay

Constrained by Higgs decay from ILC

can be tested 3 sigma level

Electroweak baryogenesis and LC (mini-review)

Talk by Yasuhiro Okada

EW baryogenesis offers an important connection

between cosmology and particle physics

EW Baryogenesis

Strong 1st order phase transition is required

Spharelon condition should be satisfied

BUT SM with only CP-phase in KM-matrix and

cannot satisfy the condition

New physics around 100GeV - 1TeV

Examples of new physics for EW baryogenesis

1) MSSM with light right-handed stop

new CP violation sources phase of

Numerical results on baryon number

C.Balazs et al., 2005

LC physics

Strong 1st order phase transition occurs for

Large deviation of O(10%) for Higgs triple coupling from that on SM

Compare:

MSSM with light stop

O(6%) deviation

2) Two Higgs doublet model

Correlation between Spharelon condition and deviations of

the Higgs triple coupling from that of SM are examined

Precise measurement of Higgs self coupling ILC

Little Higgs Models (mini-review)

Talk by Jeonghyeon Song

EW scale stability (in non-SUSY)

Constraints from precision measurements is most likely 10 TeV

1% fine-tuning is needed: little hierarchy problem

Little Higgs Model solves the problem

Higgs boson as a pseudo-NG boson

No quadratic divergence at 1 loop level cancelled out by new heavy particles

Existence of new heavy SM-like gauge boson & fermions

interesting targets for ILC

Some Little Higgs models: Littlest Higgs, simplest Little Higgs, etc.

``Littlest Higgs model with T-Parity’’ would be the most interesting one

Under T-parity: SM particle even

Heavy gauge boson (W’, Z’, A’) odd Similar to R-parity

Lightest T-parity odd particle is stable and DM candidate!

Also, some phenomenologically dangerous interactions among

SM particle and new heavy particles are switched-off by T-parity

Con

sist

ent w

ith

WP

AM

Partially composite Two-Higgs-Doublet models

Talk by Don-Won Jung

Top condensation model dynamical EW symmetry breaking model

composite Higgs model

Top quark gets its mass by its condensation

Drawback predicted top mass is too heavy > 200 GeV

To cure this problem lower top condensation value

Idea: Two Higgs doublet model One composite

One elementary

We can take

Top mass can be consistent with exp.

Effective description of this model

two Higgs doublet model with some constraints on parameters

originated from compositeness of one Higgs doublet

(compositeness condition at the composite scale )

Measure the model parameters at ILC

M4×S1/Z2

R

Minimal setup

I. Compactification scale R is constrained by LEP (1/R > 300 GeV)

II. Z2-orbifolding is required for produsing the chiral fermion at 0-mode.

From a 4-dim point of view, UED contains SM particles and their KK-modes(gauge) γ, W, Z, γ(n), W(n), Z(n)

(lepton) Li, Ei Li(n), Ei

(n)

(quark) Qi, Ui, Di Qi(n), Ui

(n), Di(n)

(higgs) h H(n)

nth-KK particles m ~ n/R

UED has KK-parity [+(-) for even (odd) n](momentum conservation of 5th dim.)

I. The lightest KK particle (LKP) is stable.

Dark matter candidate

II. Single KK particle (odd n)

cannot be produced.

UED has KK-parity [+(-) for even (odd) n](momentum conservation of 5th dim.)

I. The lightest KK particle (LKP) is stable.

Dark matter candidate

II. Single KK particle (odd n)

cannot be produced.

1

2

Resonant signatures of universal extra dimension model at LC

Talk by Shigeki Matsumoto

Universal Extra Dimension (UED) model SM in TEV scale extra-dimensions

1st KK spectrum

Spectrum of 1Spectrum of 1stst KK KK modesmodes

Spectrum of 1Spectrum of 1stst KK KK modesmodes

UED has only two new-physics parameters. R : Size of extra dimension, Λ： Cutoff scale

UED has only two new-physics parameters. R : Size of extra dimension, Λ： Cutoff scale

No CP & Flavor problemsNo CP & Flavor problemsAll interactions in UED are determined by those in SM.All interactions in UED are determined by those in SM.

1/R = 500 GeV ΛR = 20

The spectrum of 1st KK modes in the modelis very similar to that of super-particles in MSSM (mSUGRA).

It is difficult to distinguish between these two models at LHC.

if UED is actually realized

Kinematics are essentially same !!

We need a lepton collider such as ILC.

Resonant signatures of Resonant signatures of UEDUED

Resonant signatures of Resonant signatures of UEDUED

UED has a structure similar to SUSY modelsUED has a structure similar to SUSY models What is a difference?What is a difference?

I. ∃higher KK modes, II. Difference of spins between 1st KKs & Super-particles

There are resonances originated from these differences !!(The resonances does not appear in supersymmetric models.)

There are resonances originated from these differences !!(The resonances does not appear in supersymmetric models.)

e+

e-

Z(2)

L(1)

L(1)1-loop

e+

e-

γq(1)

q(1)

q

q

B(1)

B(1)

quakonium

I. II.

Cross section of resonancesCross section of resonancesCross section of resonancesCross section of resonances

We can distinguish UED from MSSM by using resonances.We can distinguish UED from MSSM by using resonances.

We can determines model parameters such as R &Λ. 1/R Overall locations of resonances, Λ Relative distance between the locations, their widths

We can determines model parameters such as R &Λ. 1/R Overall locations of resonances, Λ Relative distance between the locations, their widths

0.1

1

10

e+e- Z(2) μ+μ- + E

(pb)

846 850 854(GeV)

1/R = 400 (GeV)ΛR = 20

e+e- b(1)b(1) bb + E 1/R = 400 (GeV)ΛR = 20

930 935

0.01

0.1

1

(GeV)

(pb)

Hunting Resonances in e+e- mu+ mu- at LC with beamstrahlung and ISR

Talk by Sreerup Raychaudhuri

Randal-Sundrum model: 5 dim gravity model with warped geometry

Model parameters:

Interactions with SM particle:

KK graviton tower:

If resonant production of KK gravitons are possible!

Beam effects at LC

Radiation phenomena: initial state radiation (ISR)

beamstrahlung

cause large energy loss and disrupt the focusing of the beam

This is nuisance and cannot be completely eliminated

Idea: this may be useful for resonance hunting

LC energy is fixed off-resonance

ISR and beamstrahlung will cause effective beam energy spread

might excite the resonance of X

Similar to the effect of ``radiative return’’ of the Z-pole at LEP 1.5

LC with

Useful for multi-resonance case

Tower of KK gravitons in RS model

LC with

Measurement of resonance points

Probing anomalous VVH couplings at an e+e- collider

Talk by Rohini Godbole

In the SM,

In New Physics model Higgs may have different CP properties

wider range of allowed masses

It is important to probe its CP properties through VVH couplings

in model independent ways

Numerical analysis for ZZH and WWH anomalous couplings

ZZH vertex WWH vertex

Calculation of the six-fermion production at ILC with Grcft

Talk by Yoshiaki Yasui

Upgrade of GRACE system

GRACE: the computer code which performs the automatic calculation

of the Feynman amplitudes

6 f, 8f and more final states are important at LC studies

In principle, GRACE can calculate these processes

BUT… very slow

Upgrade GRACE to implement new algorithm to construct

sub-sets of the sub-graphs automatically

Grcft : upgrade version of GRACE

O(5-100) times faster than GRACE

4. Conclusions

There are lots of well-motivated New Physics whose scale lies

around 100 GeV -1 TeV scale.

This range is accessible at future colliders: ILC and LHC.

ILC has a great advantage to specify the new physics model uniquely

and to measure model parameters and new particle properties precisely.

LHC is planed to start running from 2007. Before LHC, we have to

have done many LC physics studies.

To do so, collaborations among theorists and experimentalists are very

important. Theorists (experimentalists) should recruit experimentalists

(theorists) and push forward with the ILC projects.