20080906-e

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14th General Meeting of the ILC Physics Subgroup Meeting
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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)

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Opening Comments
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Reports from Subgroups
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[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)
Status:
- 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
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}
- 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

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

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3) TTH
6-jet+lepton: Yonamine
8-jet: Tanabe
3-1) TTH (Reported by T.Tanabe)
Status:
- 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)
Status:
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.

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[B] New physics
1) Model Discrimination @ 1 TeV (II) (Reported by T.Saito)
Status:
- 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)
Status:
- 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)
Status:
- 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:
500fb^-1@500GeV
1st KK: 0.4%, 2nd KK: 20.3%
500fb^-1@1TeV
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.

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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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*) Next target is Beijing LCWS.
Speakers:
Tanabe, Ono, Takubo, Suehara, Saito, Yoshida, Harada, Asano, Junping.
*) Physics-Accelerator joint meeting
joint meeting.
Theory
Experiment
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:
http://www-jlc.kek.jp/subg/physics/ilcphys/

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