20080906-e

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10th General Meeting of the ILC Physics Subgroup Meeting
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June 13 (Sat) at Room 425, Building 3, KEK
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Attendants
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H.Ono (NDU)
D.Harada (Sokendai)
R.Yonamine (Sokendai)
T.Suehara (ICEPP)
T.Tanabe (ICEPP)
S.Kanemura (Toyama)
S.Matsumoto (Toyama)
Y.Takubo (Tohoku)
T.Saito (Tohoku)
K.Yoshida (Tohoku)
M.Asano (Tohoku)
H.Yamamoto (Tohoku)
J.Tian (Tsinguha)
Y.Okada (KEK)
K.Ikematsu (KEK)
H.Ito (KEK)
K.Fujii (KEK)
N.Maeda (Hiroshima)

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Reports from Subgroups
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1) ZHH
1-1) ZHH -> qqHH full simulation (Reported by Y.Takubo)
Mh=120GeV
HHqq : 157 ab
BG total: 224 fb
2 ab^-1
Status:
- Event selection
MLP in TMVA (Neural Net)
Epoch: 500
Rec. Mt, Rec. Mw, Y-, Thrust, Nb(H1), Nb(H2), Nb(Z)
- Signal: 27.2
BG: 82.1
--> significance 2.6
bbcssc: 37.6
bbcsdu: 14.3
- With Nbc <= 2
--> significance 3.0 sigma
bbcssc: 27.4
bbcsdu: 12.0
Q: In quick simulator analysis, BG was much lower.
What is the difference between the quick sim. and full sim.
A: Will investigate.
Next Step:
- tbtb BG first with the existing sample created with an incomplete generator.
- Investigate the difference from the quick simulation results.

2-2) ZHH (Reported by J.Tian)
Status:
- ZHH -> qqbbWW* moe
WW* -->qqqq: 45% (today's topic)
WW* -> lnuqq: 45 % (not yet)
Looked at ymax, Mh1, Mz, Mw1, Mh2
--> Signal = 1.1, BG (tt) = 2644
--> impossible!
- ZHH - > llbbbb mode
Looked at Ymax, Mh1, Mh2, Mz, Evis
Next Step:
- more BG, ZZZ, tbtb
- optimization of cuts and NN
- WW* -> lnuqq
- full simulation
Q: What is the b-tagging condition?
A: One 2-sigma-off-vertex track

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2) ZH subgroup
2-1) Br(H->cc) analysis (Reported by K.Yoshida)
Status:
- Event Selection
~40% signal efficiency
- Results
delta Br(H->cc) = 13.8%
Next Step:
- Make rBG free in the template fitting.
Q: What was the previous value?
A: delta Br(H->cc) = ~30%
Q: What is the main difference in the analysis?
A: Invariant mass cuts to improve S/B.
Q: There was a discrepancy between SiD and ILD. Is this problem resolved?
A: SiD assmed 4 times bigger production crossection for the singal, which was wrong.
C: You should inform SiD people about this.

2-2) ZH analysis (Reported by H.Ono)
Status:
- Data sample
Now using standard ILD sample with the standard SM BG.
- Event Selection
Same as the GLDPFA analysis
- nunuH
--> S= 4582 with eff =24%
BG = ~5600
--> Mh = 120.8 +/- 0.11 GeV
- qqH
--> S = 9491 with eff = 18%
BG = 19000
5C (4C+Mz) fit
--> Mh = 10.76 +/- 0.1
Next Step:
- Fitting fun. kinematic fitting, selection
- flavor tagging
- First concentrate on H->bb and then H -> WW*.

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3) TTH (Reported by R.Yonamine)
Status:
- Effect of polarization
- Currently working on the l+6j mode (1ab^-1)
(Pole-, Pole+) = (0,0)
TTH: 29 TTZ: 7 TT: 12 -> significance: 4.2
(-0.8,+0.3)
TTH: 49 TTZ: 5 TT: 20 -> significance: 5.7
(+0.8,-0.3)
TTH: 27 TTZ: 12 TT: 9 -> significance: 3.9
Next Step:
- ttg->ttbb BG (~ 0.7fb) --> probably OK if Mbb ~ 120 GeV is required.
- 8-jet mode
- H->WW*
- Full simulation
Q: The ttg BG generator has been the priority for long time but not yet done.
Is there any concrete plan to change the situation?
A: We will decide who is going to do this in two weeks.

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4) AA->HH (Reported by N.Maeda)
Status:
- Sensitivity study
1st assume 100% efficiency for S and no BG
--> E_AA=260-270 GeV is optimum.
BG (WW: 90 pb), while S ~ 0.04 fb
--> E_AA below tt BG
--> signal cross section x luminosity -> 16 events / year (10^7 sec)
(sigma_eff(S) = 0.013 fb, (sigma_eff(BG) ~ 12pb)
- Event Selection
chi2 & b-tag
-> n-sig method: eta(B) = 1.5x10^{-6}, eta(S) = 0.16
-> combined with chi2 cut and Ech > 2 GeV
0 BG event remained from ~45x10^{6} events
9 signal events for 5 years (eta(S)=0.11) -> 2.9-sigma
Next Step:
- HH -> bb WW* (BR=0.18)
- To study remaining BG events with MC truth
- Other BG (AA -> 4b)

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5) New physics subgroup
5-1) Nightmare Scenario (Reported by S.Matsumoto)
Naturalness requires lambda <= 1TeV while Exp requrires lambda >= 10TeV
case 1: susy, LHT, gauge-Higgs unification
case 2: 1% fine tuning -> lambda=10TeV --> nightmare
--> Veltmann condition: accidental canncellation between higgs loop & top loop
WIMP DM
Omega_DM h^2 ~ 0.1pb c / <sigma v> --> m_DM = 10GeV - 1 TeV
Singlet DM with a Z2 symmetry
S, F, V (J=0, 1/2, 1) --> Any signal through H : Higgs portal scenarios
Status:
- Theory
Boltzmann eq (exactly solved)
CDMS, XENON, XMASS + S-CDMS, S-XENON bounds
Invisible decay
@ LHC (visible if Br > 0.25 WBF with 30fb^-1)
@ ILC (visible if Br > 0.03 ZH recoil)
--> Results:
Direct search covers a large area
ILC has a potential to cover some important region (Higgs funnel).
Next Step:
- ILC x-section
- mh=150GeV
- IceCube
- Improvement of invisible width analysis @ ILC --> experimentalists
- m_DM >mh/2 case --> experimentalists (Honda)

5-2) Majorana Nature (Reported by S.Kanemura)
Status:
- delta m^2 ~ 8 x 10^-5 eV^2, 3 x 10^-3 eV^2
Leff = (cij/M) nu_L^i nu_L^j phi phi
--> m^nu_ij = (cij/M) v^2 < 0.1 eV (v=<phi>=250GeV)
--> seesaw @ tree level
m^nu_ij = yi yj v^2/M --> M ~ 10^11-15 GeV
loop (e.g. 3-loop) suppresion
--> M ~ 1 TeV
- Model Predictions
M.Aoki, SK, O.Seto : PRL102, 051805 (2009): 3-loop
TeV scale nu_R + Extended Higgs sector with (exact) Z2 symmetry
N_R, 2HDM (phi1, phi2) +singlet scalars (eta0, S+) --> eta0 becomes DM
Additional Z2 (softly broken) to avoid FCNC
Neutrino data prefer a light H+ <200GeV -> Type X
--> Data can be fit.
--> m_DM ~ 50GeV, m_S+ ~ 400 GeV, m_H+/A < 200GeV, m_N_R ~ 1TeV
Br(h->DM DM) = 36% for m_DM=48 GeV (eta0=DM)
A/H -> tau tau dominates for tanb > 2.
A large (20-40%) quantum correction to hhh coupling --> Testable @ ILC?
Majonara nature
--> e- e- --> S- S- with Majorana N_R exchange
--> sigma ~ 100 pb!!
Next Step:
- Fill up details and write a paper.
Q: X-section for direct production?
A: XMASS
Q: What about LFV?
A: B(mu->egamma) ~ 10^-11

5-3) N_R in XD (Reported by T.Saito)
N_R: gauge singlet
Usual seasaw
m_nu = v^2 y^2 / 2M ~ 0.1eV
--> for y = 1, M = 10^14GeV
--> y=10^-6 -> M=10^2GeV
--> y=0.1 M~100GeV if N lives in XD
Status:
Preparing a generator e+ e- -> nu N
Next Step:
- Complete the generator
- BG generation
- Analysis
C: Use e nu W generator as the start point.
C: A lot of discussions on the justification of the truncation of KK towers.

5-4) Tau pair (Reported by S.Taikan)
Status:
- sigma, AFB and Pol(tau) measurements
Progress
improved selection cuts
more BG (Bhabha, two-photon tau tau)
better mode selection with NN
optimal observable for Pol(tau) measurements
--> signal increase ~ 20%
Next Step:
- Pol value inconsistent with the MC input -->
- a1 mode
- paper --> Next JPS meeting?

5-5) Top (Reported by K.Ikematsu)
Full simulation studies with ILD framework
IDAG request: AFB in 6-jet mode
Status:
Charge ID using B from b-jet
--> efficiency ~ 28% with putiy 75%
--> AFB = 0.334 +/- 0.0079 for (Pol(e-), Pol(e+))=(-0.8,+0.3)
--> Problem with the measured AFB
Observed AFB strongly affected by ISR and beamstrahlung
Next Step:
- Charge ID with charm from W
- Investigate the discrepancy the Input value
- New physics subgruop: l+4-jet
-> Angular analysis
- A_FB (vertex charge)
--> Z' studies together with tau tau
Q: Is there any way to utilize B0?
A: Jet charge.
C: High Pt lepton from B decays.
C: K/pi separation with PID?
C: K/pi separation with mass assignment?

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The slides shown at the meeting is available from
http://ilcphys.kek.jp/meeting/physics/
see them for details.
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Discussions on future direction and mile stones
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Meeting Schedule:
Next bi-weekly meeting
The bi-weekly meeting will be merged into the weekly software meeting
on Thursday at 10:00AM (video conference ID = 31300).
The first half will be on physics analyses and the second hlaf will be on software/optimization
so theorists can attend the first part only.
Slides for this weekly meeting will be put on the software meeting web page from now on, while
slides for the general meetings will be put on the physics WG page as before.

Next general meeting (2009/09/19 9:30) -> Link with Detector Meeting

Proceedings:
"Proceedings of the ILC Physics WG Meetings", KEK, May, 2007 ~ June, 2009
Proceeding deadline: the end of June 2009:
Anybody can contribute even if he or she was not present at the meeting.
Contributors are encouraged to include most updated results at the time of submission
of their proceedings papers.

Future Directions:
Generic DM studies:
StdHEP output for DH and LHT events --> Suehara/Takubo
TTH/ZHH:
Generator development of ttbb and its StdHEP output --> Tanabe/(Fujii)
Generator development of ttZ --> Ikematsu/(Fujii) with consultation from Sumino/Kiyo (@KEK from 8/1)
SUSY (Suehara):
Paper being prepared by Jenny List (DESY)
ZH (Tohoku/NDU)
H.Ono will take over BR studies: (template fitting with all modes combined).
TT/tautau (Ikematsu/Suehara):
AFB(tt) requires lepton+4J mode --> Ikematsu
Will write 2 exp papers (Ikematsu/Suehara) + 1 th+exp paper (N.Okada)

Working group web page:
http://www-jlc.kek.jp/subg/physics/ilcphys/

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