14th General Meeting of the ILC Physics Subgroup Meeting
0) Attendants:
H.Ono (NDU)
T.Tanabe (ICEPP)
Y.Takubo (Tohoku)
T.Saito (Tohoku)
M.Asano (Tohoku)
D.Harada (KEK)
Y.Okada (KEK)
K.Fujii (KEK)
E.Kato (Tohoku)
K.Yoshida (Tohoku)
R.Yonamine (Sokendai)

Via video
J.Tian (Tsinghua)

Opening Comments
Reports from Subgroups
[A] Symmetry breaking & mass generation
1) ZH subgroup
- qqH: Ono
- nunuH : completed by Yoshida in LOI
- llH : being looked at by Yoshida
mh=120GeV, 250fb^-1@250GeV, Pol(e+,e-)=(+30%,-80%)
1-1) qqH analysis (Reported by H.Ono)
- Essentially the same (Egamma cut is slightly different) event selection criteria with SiD
-> efficiency = 53% (cc), 56% (bb), 44% (Higgs BG), 5% (SM BG)
- Template fitting
Investigating binning effect:
-> Try smoothing
-> Br(cc)/Br(bb) = 0.058 +/- 0.014 : 23.4% (12.3% before smoothing)
-> due to the distortion by smoothing.
-> set threshold for smoothing by checking the number of events in each bin.
-> optimized the threshold value
-> delta BR(cc) = 12.6+/-1.2%
-> some inconsistency with Yoshida san's analysis.
Next Step:
- Investigate the difference from Yoshida san's analysis.
1-2) llH analysis (Reported by K.Yoshida)
- Lepton ID
Ecal/Etot, Etot/p, isolation cuts
-> (efficiency, purity) = 88.3% (82.9%) for l=e, 96.4%(95%) for l=mu
All cuts (+Evis, Mll, costh, Mjj-Mrecoil)
-> efficiency ~ 15% for both l=e and mu
- Br measurement
-> delta rcc= 22%, delta rbb=3%

1-2) ZH -> nunuH followed by H->WW* (Reported by Y.Takubo)
N.Hodgkinson, N.Okada, K.Ikematsu, and K.Fujii
- 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}
- MCconditions
mh=120GeV, 250fb^-1@Ecm=250GeV -> Br(H->WW*)=15%
Polarization: use (Pol_e-,Pol_e+)= (+80%, -30%) to suppress WW BG.
- Event selection
mh, mm, cos_h, y-value, Etk<30GeV, Nb<=1 -> likelihood cut
-> 7.4 sigma signal --> delta sigma_ZH * Br(H->WW*) = 6.9%
Jet angle in W rest frame.
- Looked at phi between two decay planes by IDing charm quarks (eff_c=0.5 purity_c=0.8)
--> Reconstructed phi distribution by fitting mh distributions for different phi bins.
--> Asymmetry seen as expected.
--> The number of events after c-tag seems strange.
Next Step:
- Investigate the inconsistencies in the numbers of selected events.
- Prepare a generator with anomalous couplings and see how reconstructed distributions respond
to the change in the couplings

2) ZHH
ZHH -> qqHH : Takubo
ZHH -> llHH : Junping
2-1) ZHH full simulation status (Reported by Junping)
- Full simulation
Analysis tools have been prepared for the Marlin framework:
3 new processors now available.
Next Step:
- Do physics.

3) TTH
6-jet+lepton: Yonamine
8-jet: Tanabe
3-1) TTH (Reported by T.Tanabe)
- Aim
Direct top Yukawa coupling measurement at 500 GeV
- New features
Included QCD threshold corrections to both the signal and BG.
- delta g/g ~ 13% for both modes with Pol(e+,e-)=(-0.8,0.3).
--> combined -> 9%
Next Step:
- Complete the paper and submit it.
- Then full simulation.

4) AAHH group (Reported by D.Harada)
New physics effects from THDM, scalar LQ, chiral 4th generation scenarions
SM limit (sin(alpha-beta)=-1)
Non-decoupling limit (M=0: gauge invariant mass)
rho-parameter constraint -> mH=~mA=~mH+/-
- THDM (new particle = B) -> +ve effect
The cross section has a structure coming from WW (<< 2mh), tt, HH thresholds
The effect coming from SM-NP interference
- S-LQ (new particle = B) -> +ve effect
- Chiral 4th (new particle = F) -> -ve effect
--> generally the effects could be very large (> 100%) for the self coupling.
Next Step:
- Maeda san is transferring his knowlege to Kawaguchi, a new M1 student.
- Improve jet clustering which is essential to suppress ZZ BG.
C: The region where LHC can detect the effects is already excluded by Tevatron.
low mh region -> qq -> V h
high mh region -> gluon-gluon -> h
Low mh will be difficult at LHC.

[B] New physics
1) Model Discrimination @ 1 TeV (II) (Reported by T.Saito)
- Ew endpoints
-> delta m_DM < 10% if X-section = 200 fb with 500fb^-1.
- Production angle distributions
--> |cos th1| vs |cos th2|
--> Template fitting
--> Possible to discriminate different models.
--> Some errors seem too small.
--> Chi2/ndf values seem strange.
- Threshold scan
Fit region; 740~800 GeV assuming the same X-section @ 1 TeV
--> model discrimination seems possible with 200 fb.
Next Step:
- Check out the numbers.
- Prepare for the publicatoin.

2) LHT: ZHZH (Reported by E.Kato)
- MC Conditions
Same as the previous LHTpublication
- Event Selection
Significance > 100!
- Mass fitting
Found multiple solutions.
--> Trying to understand the reason.
Next Step:
- Understand the two solutions by investigating MC truth distributions
- Simultaneous fit to ZHZH and WHWH

3) Right-handed Neutrino (Reported by T.Saito)
Seasaw: Mnu = v^2 y^2 / 2 M_N
--> XD can make y small
--> M_N = (2n-1)/2R in TeV scale XD model --> can be as light as O(100GeV)
- Setup
Seasaw: Mnu = v^2 y^2 / 2 M_N
--> XD can make y small
--> M_N = (2n-1)/2R in TeV scale XD model
--> M_N = O(100GeV) and y = 0.1 possible
--> M_N = 150GeV to avoid the LEP constraint.
- Event selection
*) e nu qq (1st KK: 150 GeV, 2nd KK: 450 GeV)
Degenerate case:
1st KK: 0.4%, 2nd KK: 20.3%
1st KK: 0.7%, 2nd KK: 2.7%, 3rd KK: 10.1%
Inverted case has similar precisions
In the normal case, only 1st KK can be observed.
Next Step:
- Error estimate for the mass fit.
- tau mode.

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

Discussions on future direction and mile stones
*) Next target is Beijing LCWS.
Tanabe, Ono, Takubo, Suehara, Saito, Yoshida, Harada, Asano, Junping.
*) Physics-Accelerator joint meeting
joint meeting.
with some review talks on detector R&D.
--> Bring this idea to the EB meeting of the detector R&D group.
*) Conveners
Uozumi san left & Ikematsu san will leave soon.
--> Tanabe san & Yonamine san

Meeting Schedule:
Next general meeting (2010/05/15 10:00)

Working group web page:

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