7th General Meeting of the ILC Physics Subgroup Meeting

A Summary of The 7th General Meeting of the ILC Physics Subgroup
Nov. 8 (Sat) at Room 425, Building 3, KEK
0) Attendants:
T.Kusano (Tohoku)
R.Sasaki (Tohoku)
M.Asano (ICRR)
T.Honda (Tohoku)
K.Ikematsu (KEK)
H.Itoh (KEK)
Y.Okada (KEK)
N.Okada (KEK)
D.Harada (Sokendai)
T.Suehara (Tokyo)
Y.Sumino (Tohoku)
H. Ono (NDU)
T.Watanabe (Kogakuin)
N.Maeda (Hiroshima) via TV connection
K.Fujii (KEK)

Reports from Subgroups
1) ZHH
--> to be presented in the Higgs session.
1-1) HH nunu: 120GeV (Reported by Y.Takubo)
--> to be presented in the Higgs session of LCWS08.
- sigma_S = 40 ab
- Problem with the Madgraph generated top has been solved.
--> intermediate Ws are needed for the hadronizer.
--> Use DECAY in cascade: t -> b W -> W -> ffbar
- Event selection
Mass cut
Missing Pt
4-b requirement
vertex mass > 1 GeV
- Status of S/B
7.3(ZHH) + 1.8(ZZ) + 29(tt) +0(tbtb) + 0(ZH)
--> isolated lepton veto
Next Step:
- Increase tt BG statistics
- Try isolated lepton veto
- Look at remaining BG events with event display
- Other decay


2) ZH subgroup (H.Ono)
- Full detector simulation, continue with Ecm=250GeV case
Has been using Jupiter/Satellites (GLDPFA)
--> Established an analysis sequence with PandoraPFA.
- 2-jet mode (250fb^-1)
Q: Does the Z mass cut affect H mass reconstruction?
A: Will check the effect.
C: Need to
Gamma= 4.07: PandoraPFA (3.71: Cheated) GeV @ 250 GeV
Q: Reconstructed Mh seems to be lower than the input.
A: Will check calorimeter calibration constants.
- 4-jet mode (100fb^-1)
Gamma=4.8 GeV: PandoraPFA (3.75 GeV: CheatedPFA) @ 250 GeV
with Darham jet finder.
Next step:
- Comarison with GLDPFA.
- BR measurements with vertex tagging.
- Kinematical fitting.
C: Important to measure decay angular distribution of Z to separate T/L.

3) TTH (Reported by K.Ikematsu)
-> to be presented in loopverein, Top, and QCD session of LCWS08.
TT to demonstrate feasibility of multi-jet reconstruction with PFA.
l+6-jet mode
- S: 0.44 fb, BG (ttZ): 0.71 fb
- Study with cheated jet finder
--> This sets the ultimate goal of event selection
- ttbb BG generators prepared.
Q: Why ttbb_gluon < ttbb_nogluon?
- Event selection
isolated lepton
mass cut
Q: What is the cone angle?
A: Will check the cos theta value and post it to the mainling list.
Next Step:
- Study further the tt, ttg BG
- Realistic jet finder

4) AA->HH
4-1) Theory (Reported by D.Harada)
--> to be presented in the Higgs/AA joint session.
--> Contents will be essentially the same as in the last meeting.
Nest step:
- Will extend the study to gluon gluon at the LHC.

4-2) Exp (Reported by N.Maeda)
--> to be presented in the Higgs/AA joint session by T.Takahashi.
- Sensitivity study
1st assume 100% efficiency for S and no BG
--> E_AA~300 GeV is optimum.
2nd with BG (WW: 90 pb)
--> 10^ suppression for BG is necessary even with 100% efficiency for S
to achieve sensitivity ~ 3.
- Signal study
mass cut, b-tag, ...
- BG study (WW: 90 pb)
generated BG with Grace thanks to Kurihara-san.
2D chi2 cut, Ntracks, sorted cosHiggsj1j2 cut
--> Cut efficiency S: 730/1000, BG: 59/1000
Next Step:
- Implement luminosity spectrum.
- BG study:
cross section, detector simulation, analysis
- Take into account luminosity distirbution with CAIN (so far delta fun).
Q: Why are Ntracks distributions different for WW and HH?
A: Mh > Mw and h->bb.
C: Use the number of charged tracks.


5) LHT
5-1) Theory (Reported by M.Asano)
--> to be presented in the new physics session.
- Preparing a peper with experimentalists.
--> Nov.27-29 special camp for drafting the paper
- Trying to interpret Pamela positron excess
--> Non-thermal contributions.
--> Anti-proton excess is also expected.
--> maybe OK considering ambiguity.
Next Step:
C: Should consider A_H decay (T-parity violation via anomaly).
- AH -> boson bson (e.g. Z gamma)
- eH- eH+ pair production
- t T+ threshold

5-2) Exp: e+e- -> Z_H A_H (Reported by T.Kusano)
--> to be presented in the new physics session.
Goal: mass, cross section determinations
-> m(AH) and m(ZH) from E(h) min and max.
- Z_H -> A_H + h (100%) @ 500 GeV
AH=82GeV, ZH=369GeV, h=134 GeV
H decay : BR(bb)=55%, BR(WW*)=26%, BR(cc)=6.3%
- ZZ -> bbnunu/ccnunu BG study
- event selection
Mh cut, cos(th) cut
--> S/sqrt = 5.4
- Edge fit -> masses
--> M_AH = 80.8 +/- 1.8 GeV (No BG)
M_ZH = 370 +/- 2.9 GeV (No BG)
--> M_AH = 80.1 +/- 7.3 GeV
M_ZH = 366 +/- 17. GeV @ 500 fb^-1
Nest Step:
- BG study: tt, Zgamma
- Improve the fitting function.
- Draw a contour.
- Determine F from cross section.

5-3) Exp: e+e- -> W_H W_H (Reported by R.Sasaki)
--> to be presented in the new physics session.
Mass, WH production angle -> spin, helicity angle dist. of W decay
- m(WH) = 368 GeV, m(AH) =82 GeV
sigma_S=122 fb @ Ecm=1TeV with 500 fb^-1
- dominant BG: WW, eeWW
- Wiht detector simulation studying event selection to fight WW BG.
mW chi2 cut, missing PT --> S/B = 7
- M_AH = 82.42+/-1.09 GeV, M_WH=368+/-0.9 GeV
Q: Where is the fine structure in the anglular distribution coming from?
A: Maybe statistics.
C: Should plot |cos| instead of cos.
Next step:
- Investigate past chargino studies.
- BG study.
- M_NuH from production angle and total cross section.

6) New physics subgroup
--> to be presented in the new physics session.
6-1) Theory (Reported by N.Okada)
Extra Higgs doublet (dark doublet), eta, & nu_R both with Z2 odd parity
--> Only ordinary Higgs gets vev.
--> Seesaw and DM (eta_I).
Implications for ILC/LHC experiments
--> If eta_I lighter than Mh/2 --> invisible Higgs decay
--> eta^+/-, chi^+/-, WH^+/-
J=0, 1/2, 1
--> production angle distributions tell the spin
Q: Constraints from S,T?
A: No problem if M_etaR = M_eta^+/- (custodial symmetry for (eta^+, eta_R^0, eta^-)).
Q: If h decay is totally invisible, what happens to LHC?
A: WW fusion ->h-> invisible?
Next step:
- mass determination
- production angle distributions.
- W_L/T from W decay helicity angle.
- W charge ID in jet mode.
- Generator preparation for eta^+/-
--> paper with simulations (SUSY+LHT+eta^+/-)

6-2) Exp (Reported by T.Suehara)
--> to be presented in the new physics session.
Chargino/neutralino separation (chargino -> W+LSP, neutralino -> Z+LSP)
- mass fit --> delta M <~ 1 GeV with 500 fb^
- production angle
- W/Z decay helicity angle
- Cross section and A_pol
Jet clustering:
2ndary vertices as heavy flavor jet core
--> to be presented in the sim/reco session.
- Cross section measurements with full SM BG.
- Anglular distirbutions
- Translate experimental precision to parameter errors.
- Sensitivity to Z' effects
- Jet clustering: vertex finder.

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

Discussions on future direction and mile stones
A workshop with proceedings/LC notes/arXiv open to wider public.
--> 8th general meeting as the wokshop, Jan. 21, 2008, 9:00-17:00
--> Include all the achievments, not just new results, of the working group activities in the proceedings.

The next bi-weekly on Dec. 4 (Thu), 13:00 as usual.

Working group contact persons:
K.Ikematsu, S.Uozumi, Y.Okada, H,Ono, S.Kanemura, Y.Takubo, K.Fujii, T.Suehara

Working group web page:

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