summary on physics session the 8 th acfa workshop july 14, 2005, daegu, korea nobuchika okada (kek...
TRANSCRIPT
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
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.