A Summary of The 30th General Meeting of the ILC Physics Subgroup
Mar.16, 2013 (Sat) at Room 425, Building 3, KEK
0) Attendants:
Present at KEK:
T.Tanabe (Tokyo)
A.Dubey (Tohoku)
T.Horiguchi (Tohoku)
S.Watanuki (Tohoku)
K.Ichikawa (IPMU)
H.Ono (NDU)
S.Kawada (Hiroshima)
R.Yonamine (KEK)
H.Yokoya (Toyama)
K.Tsumura (Nagoya)
J.Tian (KEK)
M.Asano (U.Hamburg)
S.Matsumoto (IPMU)
A.Ishikawa (Tohoku)
T.Nabeshima (Toyama)
S.Kanemura (Toyama)
M.Kikuchi (Toyama)
M.Nojiri (KEK)
M.Kurata (Tokyo)
T.Yamada (Tokyo)
K.Fujii (KEK)

Opening Comments
1) Higgs BR Studies for DBD (H.Ono)
- BR paper published! EPC 73, 2343 (2013)
- vvh @ 1TeV
Included ea -> 3f, 5f, aa->4f BG
Added E_BCAL < 50 GeV to suppress these BG processes
- Results with 1ab-1
bb: 0.39%
cc: 3.9%
gg: 2.8%
mm: 31%
- Extrapolation to mh=125GeV
- Results with 250fb-1@250GeV and 350GeV, 500fb-1 @ 500 GeV
bb: 1.1% 1.1% 0.62%
cc: 7.4% 7.4% 6.2%
gg: 9.1% 6.0% 4.1%
WW*: 6.4% 2.6%
tau: 4.2% - -
- new H->WW* analysis including Z->ll
d(sigxBR)/(sigxBR) = 6.9% for mh=120GeV
Next Step:
- mh=125GeV analyses
- H->ZZ*

2) ZH: H->tau tau at 250 GeV (S.Kawada)
- Previous meeting:
Z->ee: 7.4 sigmas, mm: 8.5 sigmas, qq: 25.6 sigmas
--> 28.0 sigmas => 3.6%
New updated results:
Z->ee: 8.0 sigmas, mm: 8.8 sigmas, qq: 25.7 sigmas, vv: 3.0 sigmas
--> 28.5 sigmas => 3.5%
--> extrapolation to mh=125 GeV: 4.5%
Next Step:
- 1 TeV analysis
C: mh=125GeV extrapolation is different from that by Ono-san.
Check consistency.

3) Probing wino DM at ILC (K.Ichikawa)
--> large sermon mass and small DM mass
--> AMSB allows such a spectrum
--> m_wino < m_bino < m_gluino --> wino DM.
mass difference ~ 165 MeV
A charging pair decays through annihilation near threshold even though
there is no resonance, since chargino life time is long and their wave
functions stay overlapped each other for long enough time.
--> Excess in SM-like events.

4) Higgs inflation in a radiative see saw model (T.Nabeshima)
Inert doublet (Z_2 odd scalar doublet) + v_R
--> inflation : inert doublet model
neutrino mass : seesaw
DM : Z_2 odd scalar
--> m_A ~ m_h
H+: difficult observe at LHC: too much W boson BG
A : difficult observe at LHC
--> testable at ILC:
SUSY like signals.
--> Masses of H+/- and A can be measured.

5) Radiative corrections to Higgs coupling in HTM (M.Kikuchi)
Motivation for Higgs sector extension
+ S: dark matter
+ Phi: MSSM, EW baryogenesis
+ Delta: neutrino mass
--> "h (125)" as a probe of new physics. --> needs predictions at the 1-loop level
--> Consider 1-loop corrections in HTM
SM-like h plus h++/--, h+/-, A, H
--> rho != 1 at the tree level.
Case I: H++ < H+ < A, H
Case II: A,H < H+ < H++
Case III: all degenerate
Observables to calculate:
g_hXX: X= gamma, Z, W, h
(cf) expected precision at ILC: O(1)% for hZZ, hWW, 20% for hhh
Renormalization 1: rho != 1 requires one more input parameter.
4 input parameters needed for HTM: mW, mZ, alpha_em, s2w
Renormalization 2: V(Phi, Delta): 9 parameters
Expected deviations:
hZZ, hWW --> O(1)%
hhh --> O(10)%
Next Step:
- Extend the analysis to 2HDM, Model with a singlet
- Take into account LHC constraints

6) Self-coupling 1 (J.Tian)
DBD studies for ZHH at 500 GeV, vvHH at 1 TeV have just been finished.
Key differences from the LoI time:
- much better flavor tagging: LCFIVertex (LoI) --> LCFIPlus (DBD)
- isolated lepton sélection: bbbb 0.43% (LoI) --> 0.028% (DBD)
- weighting to enhance the self-coupling diagram
SGV performs pretty good. Use it for fast simulation.
Next Step:
- Weighting including BG.
- Include two-photon BG.
- Update the analysis to mh=125GeV.
- Color singlet clustering.
- Include H->WW* (Kurata)

7) Self-coupling 2: HH->bbWW* (M.Kurata)
Signature to look for
ZbbWW* --> qqbblvqq
--> bbbbqqqq
--> bbbblvqq
--> llbblvqq
--> llbbqqqq
Combined results
--> 1 sigma significance so far.
Most significant is all hadronic channel with 4 tight b-tagged jets.
(signal is just bbhh with BG being tt, ttQQ, ttZ, tth, and ZZh)
Next Step:
- Improve analysis
- Check overlapping with HH->bbbb analysis.

8) Top pair threshold (T.Horiguchi)
MC simulations with
mt=174 GeV, 11 points with 10 fb-1 each from 340 to 350 GeV in 1 GeV step.
beam polarization: (+0.8,-0.3)
efficiency: 0.4 - 0.45, almost linear function of Ecm.
Next Step:
- Evaluate sensitivity to top Yukawa
C: Try eLpR combination.

9) SUSY extended Higgs sector and SUSY strong dynamics (T.Yamada)
Choose EWBG as a guiding principle for model construction.
--> strongly 1st order EW phase transition is required.
--> 2HDM can realize the condition but it cannot be a UV complete theory
since some coupling must blow up at a relative low scale.
--> SUSY gauge theory which provides a IR picture of extended Higgs sector
with large couplings.
IR picture:
MSSM Higgs doublets
+ extra HD + charged singlets + Z2-even neutral singlets + Z2-odd neutral siglets
EW phase transition:
light scalars: Phi_u, Omega^-, eta
--> Confinement scale: Lambd_H < 15TeV
Collider phenomenology:
Exotic scalaires and ferminons
h->gamma gamma: -O(10)% reduction from SM
self-coupling: +O(20)% or more enhancement from SM

10) Phenomenology of Inert Doublet Model at ILC (H.Yokoya)
Z_2: phi_1 -> phi_1, phi_2 -> -phi_2
v_1 = v, v_2 = 0
--> 4 additional scalars: A, H, H+, H-
--> the lightest is stable (DM)
--> 40 GeV < m_H < 80 GeV
pp -> H+H-, HA, H+/-H, H+/-A
H+/- -> W+/-H(A)
A -> ZH
possible only if m_A - m_H > 50 GeV
e+e- -> HA, H+H-
--> relatively easy to observe.
--> mass and spin determinations are possible.

11) CP mixing of Higgs (S.Watanuki)
Measure cos(theta_Z) and extract the mixing parameter, eta.
Signal sample: eta=0 and mh=120GeV at Ecm=250 GeV with (P_e-,P_e+)=(-1,+1).
Select Zh -> mmh using ZFinder + cuts on m_Z and m_rec
--> reconstructed cos(theta_Z)
Next Step:
- BG study.
- Estimate efficiency.
- Extract eta from the cos(theta_Z) distribution.
- Extend the analysis to nonzero eta samples to test the sensitivity to eta.

12) SU(2) septet mixture (K.Tsumura)
rho-parameter: guiding principle
rho=1.0004 +0.0003/-0.0004 (exp)
--> rho_tree=1
--> Pell's equation in number theory. x^2 - n*y^2 = 1
with x = (2I+1), y=2Y, n=3
--> Next minimal solution: (x_2, y_2)=(7,2) --> a septet
1 Higgs doublet + 1 Higgs septet
with U(1) breaking term to eliminate exact NG boson.
After some simplification, the model contains M_7, c_alpha, tanbeta=v2/(4v7)
- k_V >> 1 possible as compared to k_V^{2HDM} <= 1.
- mu_v > 1 and mu_gamma > 1 and mu_f < 1
consistent with ATLAS though not with the recent CMS results.
ILC Phenomenology:
- e+e- -> W+/-H-/+ --> v3[v7] ~ O(GeV) can be probed.
C: What about RG running?


The slides shown at the meeting is available from
see them for details.

Discussions on future direction and milestones
*) Meeting Schedule:
Next general meeting (2013/05/18 10:30) : Conf.ID: 539
*) Post DBD Studies:
- mh=125GeV for 250GeV, 350GeV, and 500GeV analyses.
- h->ZZ*, AA, ZA for both ZH and vvH
- Further improvement of BR measurements
- Further improvement of self-coupling measurements
- Investigate lumi upgrade options
- Studies of systematic errors
- To what precision do we need to measure Higgs properties?
- How well do we expect to control theory uncertainties for both LHC and ILC?
- Comparison of LHC and ILC reach in a generic model space

Working group web page:

Slides are available from http://ilcphys.kek.jp/meeting/physics/