Dear colleagues,

Since the 25th meeting on Apr. 14, 2012, the working group
had made significant progress, thanks to your contributions,
and we could successfully hold our 26th general meeting.

Thank you very much for those who participated in the meeting.
The following is a short summary of the 26th meeting.

if you find any mistakes or accidental omissions, please let us know.

The next general meeting will be on Sep. 8, 2012.
Sincerely yours,

Working group contact persons
A.Ishikawa, H,Ono, S.Kanemura, T.Suehara
T.Tanabe, J.Tian, M.Nojiri, K.Fujii, and R.Yonamine

A Summary of The 26th General Meeting of the ILC Physics Subgroup
Jun. 9, 2012 (Sat) at Room 425, Building 3, KEK
0) Attendants:
Present at KEK:
T.Horiguchi (Tohoku)
J.Tian (KEK)
Y.Kikuta (KEK)
R.Yonamine (Sokendai)
Y.Okada (KEK)
M.Nojiri (KEK)
K.Fujii (KEK)
T.Tanabe (Tokyo)
R.Katayama (Tokyo)
T.Yamada (Tokyo)
T.Shindo (Kogakuin)
H.Ono (NDU)
S.Kanemura (Toyama)
T.Nabeshima (Toyama)
M.Kikuchi (Toyama)
P.Roloff (CERN)

Via video conf.
T.Suehara (Tokyo)

Opening Comments
[A] Higgs Related Topics
1) ZH analysis: main decay modes (H.Ono)
- DBD physics chapter
- A list of topics to cover shown.
H -> bb, cc, gg: done --> draft final-epsilon
Kawada @ Hiroshima has been assigned to work on H->tau+tau-.
- h->bb,cc,gg
Found a slight problem in the MC sample (redoing the analysis, to be finished soon)
dBr/Br = 2.7% (bb), 7.3% (cc), 8.9% (gg) for mh=120GeV
3.0% (bb), 8.2% (cc), 9.5% (gg) for mh=125GeV
- H->WW* study (with one W*->lnu)
dBr/Br = 10.6%(l+2j) 13.2% (4j), 8.4% (combined) for mh=120GeV -> 7.2% (mh=125GeV)
- H->ZZ*
on going.
- Spin measurement
on going.
- Invisible width
on going.
Next Step:
- Publication of H->bb,cc,gg: soon
- H->ZZ*, spin measurement, invisible width
- nnH @ 1TeV

2) Theory: Extended SUSY Higgs Sector and EW Baryogenesis (T.Shindou)
Ref.: PLB706
- B, B-L -> B (sphaleron era) at high T
or B generated in 1st order EW phase transition.
- 1st order EW phase transition --> Bubble in vacuum. -> The wall violates baryon number.
In sphaleron transition conserves B-L. --> If it's too strong it will wash out B.
At the same time, the 1st order phase transition should be strong enough to produce B.
--> In SM mh<60GeV: already excluded.
phi_c/T_c \propto 1/mh^2 > 1
--> In MSSM: light stop is necessary for strong enough 1st order phase transition
--> W = lambda Phi_u,d Phi'_1 Phi'_2 (inert Higgs) preferred.
2 Z_2 even (MSSM) doublets + 2 new Z_2 odd doublets + 2 Z_2 odd charged singlets
--> Anomaly in the lamba_hhh coupling!
--> many charged but non-colored particles
--> strong coupling theory with a light Higgs.
--> Landau pole at around Lambda_H = 1~10TeV --> SU(2)_H SUSY QCD beyond Lambda_H
Q: Is perturbation theory valid?
Q: Is Z_2 exact?

3) ZHH (Junping Tian)
- Perfect jet-clustering (perfect color single clustering + perfect flavor tagging)
delta sigma/sigma = 20%
- New flavor tagging
Idea: vertexing before jet clustering
After vertexing there are two options:
a) use vertices as jet cores --> enhances not only signal efficiency but also BG efficiency
b) treat particles from a single vertex as a single particle and apply usual jet clustering
--> (b) turned out to be the better option.
--> qqhh: S:9.2 B:11
--> 8.5(9.2) 11.7(11) --> 1.9 (2.1)sigma
--> 2.3 (2.6) sigma
- Color singlet clustering
Idea: define likelihood for each combination of mini-jets in each event.
Fact: delta mh increases rapidly at around the number of mini-jets becomes around 20.
Next Step:
- Continue working on the color single clustering.

4) Radiative seesaw model from a TeV scale U(1)B-L (T.ZNabeshima)
gauge symmetry breaking
- Motivation:
U(1)B-L gauge symmetry:
common origin to tiny neutrino masses, DM mass, and stability of DM.
- Physical states
h, H, S1, S2, eta+/-
- Signals:
LHC: Z'(1-10TeV), Z'->invisible (30%)
70fb at Ecm=14TeV for mZ'=2TeV and g_{B-L}=0.2
ILC: e+e- -> e+ eta^- -> e+/- Psi_1 + Psi_1 + l-/+
--> l+missing
l=mu: M_DM <~ 64GeV --> 3-sigma signal @ 350GeV (1ab^-1)
--> 5-sigma signal @ 500GeV (1ab^-1)
l=tau: cross section is 100 times larger.
: NR @ 3-sigma level at Ecm=1TeV (3ab^-1)
C: e+e- -> eta+ eta- should be easy to study at ILC. It is like smuon pair production.

5) Renormalization of the Higgs Triplet Model (M.Kikuchi)
Ref.: arXiv:1204.1951
- Introduction
Mnu, DM, #B
--> Minimal H in SM is just an assumption.
--> Many variation of extensions of the Higgs sector depending on new physics
Type II seesaw for tiny Mnu:
Type II seesaw = SM + one triplet H
--> H++/--, H+/-, A, H in addition to SM-like h
--> rho \ne 1, renormalization of mixing angles, L violation
In SM, no nuR --> no Dirac mass
hyper charge --> no Majorana mass
--> veb_triplet should be small.
--> Interesting mass relation between triplet mass and doublet mass:
m_H++^2 - m_H+^2 = m_H+^2 - m_A^2 (exact in tree level if vev of triplet=0)
dev of triplet = O(1GeV) from precision EW studies.
- Phenomenology
No studies in the past for the large mass difference case (delta m=30GeV)
--> Case I: H++ < H+ < A,H
Case II: A,H < H+ < H++
--> Cascade decays
--> End point of transverse mass --> m_triplet
--> Possible to measure all the triplet masses at LHC.
- Radiative Correction of the Triplet Higgs Model
Radiative correction to the mass relation
8 parameters for the potential
8 physical parameters
20 counter terms
--> Case I: mh=125GeV, alpha=0 (CP even mixing) with delta m :=(m_H++-m_H+)
--> delta m~100GeV, m_H++~O(100GeV) --> delta R = O(10%): fun. of lambda4 and lambda5.
- Radiative Correction to hhh coupling
--> Case I: mh=125GeV, alpha=0
--> delta ghhh/ghhh > O(25%)
Q: What is the mass limit on H++?
A: The current LHC limit of 300GeV assumes H++ -> leptons, which is no longer correct
if H++ cascade decays for the large mass difference case considered here.

6) TTH Subgroup (R.Yonamine)
- Working on to full simulation for Ecm=500GeV, mh=120GeV, mt=175GeV
new feature: more realistic lepton ID, b-tagging.
- BG: ttZ, ttg* (g*->bbbar), tt
Q: Is btw included?
A: Judging from the cross section
- Results with the cut-based analysis
l+6J --> 3.1(3.7)-sigma for 1ab^-1 (fast sim results)
8J --> 3.4(3.7)-sigma for 1ab^-1
- Results with likelihood analysis
One mystery:
The helicity angle distribution of the H decay after pre-selection is not flat!
(pre-selection = isolated lepton ID)
l+6J --> 3.2-sigma
8J --> 3.8-sigma
--> delta gt/gt = 10%
- ttZ problem:
Fast simulation result was an over-estimate due to the old QCD correction table.
Next Step:
- Investigate the problem with the helicity angle distribution.
- Investigate the tbW BG.
C: Try other classifiers.

7) Strongly Coupled Higgs Sector in SUSY Models (T.Yamada)
- Introduction
Def. strong <=> Landau pole below Lambda_Planck
4 ways to enhance the Higgs mass
I) MSSM w/top-stop loop only | III) Today's talk
Weak <-------------------------------------------------------------> Strong
II) NMSSM w/ singlet N | IV) Fat Higgs w/ singlet N:
W incl. lambda N Hu Hd |
lambda <0.5 V lambda~2
- UV Theory
SUSY SU(2)_H gauge theory with 6 doublets = 3 pairs of doublets w/ a new Z_2 parity
g_H (QCD-like) blows up at Lambda_H --> Below Lambda_H --> pion theory like
--> Can estimate lambda(Mz) which is about 2.
--> Hu, Hd, Phi_u, Phi_d,
N, N_Phi, N_Omega: SU(2) doublet
zeta, eta : SU(2) singlet
Omega^+/- : SU(2) singlet (2 charged singlets)
--> All higgs couplings are given by lambda (determined by the underlying gauge theory)
--> In SUSY limit, EW symmetry is unbroken.
--> Lambda_H <~ 4pi x 1TeV (SUSY tadpole problem)
Another solution is to assign Z_6 parity to T_1, …, T_6.
- Extension of the theory (addition of one Z_2 even SU(2)_H, SM singlet: S)
--> no HuHd term after integrating out S and N. (M_N ~ Lambda_H)
--> no tree level enhancement of mh by large lambda.
--> but just strong enough to realize mh=125GeV in the loop level.
- Phenomenology
Under studies.
--> Br(h->VV), V=gamma, W, Z will be affected by multiple extra Higgses that strongly couple to h.
--> Large tadpole (Lambda_H^2/4pi) can be large and make mu-terms large --> extra Higgs bosons
and Higgsinos can decouple.
--> huh coupling should significantly deviate from the SM value.
--> The lightest Z_2-odd particle can be stable. --> DM.


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

Discussions on future direction and mile stones
*) Many thanks to Okada-san for having been guiding the working group activities as one of the conveners
for such a long time. Many thanks also to his successor, Nojiri-san, who will take over his role.
We hope Okada-san will keep attending this meeting, though he must be very busy now being a KEK trustee.
Meeting Schedule:
*) LCWS2012 Meeting: Oct 22-26, Arlington, Texas.
Next general meeting (2012/09/08 10:30) : Conf.ID: 801

Working group web page:

Slides are available from