20080906-e

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12th General Meeting of the ILC Physics Subgroup Meeting
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November 21 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
H.Ono (NDU)
T.Tanabe (ICEPP)
Y.Takubo (Tohoku)
T.Saito (Tohoku)
K.Yoshida (Tohoku)
M.Asano (Tohoku)
Y.Okada (KEK)
I.Fleck (Siegen)
M.Scharun (Siegen)
J.Tian (Tsinguha)
H.Itoh (ICRR)
Y.Okada (KEK)
Y.KIyo (KEK)
F.Uchiyama (KEK)
D.Harada (KEK/Sokendai)
T.Watanabe (Kogakuin)
K.Fujii (KEK)

Via TV:
N.Maeda (Hiroshima)
H.Yamamoto (Tohoku)

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Reports from Subgroups
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0) Opening Comments
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1) ZH subgroup
- qqH: Ono
- nunuH : completed by Yoshida in LOI
- qqH : Wenbiao in LIO + this analysis
- llH : being looked at by Yoshida

1-1) qqH analysis (Reported by H.Ono)
Status:
- There is large discrepancy between ILD's and SiD's.
Now using standard ILD sample with the standard SM BG.
- Analysis procedure now same as SiD.
C: Require isolation in addition to E cut for ISR gamma to further reject radiative return BG.
C: The effectiveness of # charged track cut is very different between SiD and ILD. Ask SiD why.
- Template fitting
-> Br(cc)/Br(bb) = 0.054 +/- 0.010 : 13% (Ono's original) 0.058+/-0.009 : 17% (SiD cut)
-> With finer binning, the accuracy becomes 9%.
--> Need to understand the binning effect.
Next Step:
- Understand the difference from SiD.
- Understand the behavior of template fitting
- Publication
Q: Can you use the unbinned likelihood?
A: Maybe not easy for this kind of sharp distribution.
C: Should use smoothing.
C: Or variable bin size.

1-2) ZH -> llH analysis (Reported by K.Yoshida)
Mh=120GeV
Ecm=250GeV, Pol=(-80,+30), 250 fb^{-1}
ZH -> eeH : 11.1 fb -> 2.8k events
ZH -> mumuH : 10.4 fb -> 2.6k
Status:
eeH:
- Event Selection
~70% signal efficiency
<O(1%) BG efficiency
- Results
delta Br(H->cc)/Br(H->bb) = 29%
mumuH:
- Event Selection
~88% signal efficiency
<O(2%) BG efficiency
- Results
delta Br(H->cc)/Br(H->bb) = 29%
-> Combined
delta Br(H->cc)/Br(H->bb) = 20%

Next Step:
- Reconsider about lepton ID

2-3) ZH -> nunuH followed by H->WW* (Reported by Y.Takubo)
N.Hodgkinson, N.Okada, K.Ikematsu, and K.Fujii
Status:
Looking for anomaly in the HWW vertex:
a/Lambda : HWW
b/Lambda : HW_{\mu\nu}W^{\mu\nu}
b~/Lambda : HW_{\mu\nu}~W^{\mu\nu}
Polarization: use (Pol_e-,Pol_e+)= (+80%, -30%) to suppress WW BG.
Event selection
7.5 sigma signal --> delta sigma_ZH * Br(H->WW*) = 13.3%(relative)
Jet angle in W rest frame.
- MC truth distribution has a peak at |cos theta| = 1
--> should check the MC generator
Next Step:
- isolated lepton rejection
- agnular distribution : why MC truth and rec. so different?
--> Look at decay angle distribution starting from H rest frame
instead of lab frame.
- Z->ll

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2) ZHH
ZHH -> qqHH : Takubo
ZHH -> llHH : Junping
2-1) ZHH -> ll(bb)(bb) and qq(bb)(WW*)(Reported by J.Tian)
sigma=152ab @ Ecm=500 GeV w/o beam polarization.
Mh = 120GeV
quick simulation.
2ab^{-1}
Status:
- Event Selection for llHH with MVA
--> S = 2.7, ZZZ BG = 0.48 --> significance 2.48 sigma
- ZHH -> qqbbWW* moe
WW* -->qqqq: 45%
Looked at ymax, Mh1, Mz, Mw1, Mh2
--> Signal = 1.1, BG (tt) = 2644
--> impossible! (previous results)
NN --> 1.0 signal 338 tt BG
- WW* -> lnuqq: 45 %
11.8 ZHH v.s. tt BG dominant : 4800
- Now working tt BG rejection
tt 6-jet vs ZHH : looking at difference
--> preselection
Next Step:
- Finalize preselection with NN using full simulation

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3) AA->HH (Reported by N.Maeda)
Status:
- Sensitivity study
--> 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 (HH -> 4b)
Preselection with b-tag (n-sig) requring 2 loose + 1 tight b-jets.
NN (JetNet)
chi2 (H, W), #tracks, Pt, Pl, Evis, ycut, Nb
--> 5 years
Signal = 16x5xeff = 12.5
BG = 1.5 x 10^7 x 5 = 3.9
--> 3.1-sigma (2.7-sigma for cut-based analysis)
--> Other BG: ZZ becomes the next problem.
-> 9.6 fb after folding in lumi. function -> 12000 events / yr
--> Developing ZZ generator
Next Step:
- AA -> ZZ BG generator
Z decay + lumi. function
- HH -> bb WW* (BR=0.18)
- Other BG (AA -> 4b)
- If hopeless, Mh -> 130 GeV?

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4) New physics subgroup
4-1) AMSB (Reported by T.Tanabe)
Ad: ICEPP Symposium 2010 @ Hakuba
AMSB : breaking of superconformal symmetry
- Phenomenology
- delta chi_1 = m_chi^+_1 - m_chi^0_1 ~ m_pi
- Generator
Chi^+_1 decay in Geant4
Q: How is the chargino helicity handled?
A: Should be checked. It might be lost if it is not contained in STDHEP.
- Reconstruction
a) 2 chargino tracks
b) 1 chargino track + 1 pion track
c) 2 pion tracks --> 2-photon BG?
Next Step:
- BG from full SM sample
- How well can we determine mass, mass difference, ...
- Parameters consistent with WMAP

4-2) Model Sepration (Reported by M.Asano)
Status:
Dark Matter Particle:
SUSY: R --> neutralino : J=1/2
LH : T --> heavy photon : J=1
Inert Doublet Model : Z2 --> dark H : J=0
Observables:
Masses of DM and its parent X particle
Angular distribution of X produciton --> X spin
Simulation
--> Some discrepancy in theory and MC reconstruction for LHT angular distribution
--> t-channel digaram was present.
Q: Can you construct any model with a vector X and a vector DM?
Next Step:
- Is W charge ID important?
- MC studies

4-3) Right-handed Neutrino (Reported by T.Saito)
Status:
- Setup
NuR in the bulk
--> M_NuR = O(100GeV) and y = 0.1 possible.
- Created event generator --> physsim
--> t-channel diagram dominates.
- Event selection
*) e nu qq (1st KK only)
--> Elepton cut
S: 2054 BG: 6301
--> significance : 22.5 --> delta sigma = 4.4%
*) mu nu qq (1st + 2nd KK's)
--> energetic isolated muon, M2j ~ mW, Ew
--> 1st KK: significance : 26.7 --> delta sigma = 3.7%
--> 2nd KK : significance : 17.8 --> delta sigma = 5.6%
Next Step:
- Include tt BG.
- 2nd KK for e nu W @ 500 GeV
- Higher KK (3rd and 4th) modes @ 1TeV.
- mass resolutions, decay modes -> MSN
- different parameters.
C: For 1st KK, we can study below tt threshold.

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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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*) Generalization of 2HWM by Harada, Kanemura, Asakawa, Okada, Tsumura, ...
to be presetned at the next meeting and then at the Beijing LCWS.
*) Some overview talk by theorists for the next meeting.
--> Takubo and Tanabe will find a candidate speaker.

Meeting Schedule:
Annual meeting on Dec. 2-3. (physics session on Dec.2)
Next general meeting (2010/01/16 9:30) -> Link with Detector Meeting ?
LCWS in Beijing : March 2010

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

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