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A Summary of The 29th General Meeting of the ILC Physics Subgroup
Jan.12, 2012 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
Present at KEK:
T.Horiguchi (Tohoku)
A.Ishikawa (Tohoku)
C.Calancha (KEK)
K.Fujii (KEK)
T.Tanabe (Tokyo)
T.Suehara (Tokyo)
M.Kurata (Tokyo)
S.Kanemura (Toyama)
S.Kawada (Hiroshima)
H.Ono (NDU)
F.Uchiyama (KEK)

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Opening Comments
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1) Higgs BR Studies for DBD (H.Ono)
Status:
- nnH @ 1TeV
mh=125GeV
Pol=(-0.8,+0.2)
- two-photon hadron BG
--> Optimized R for the kt algorithm --> R=1.1 for 2-jet reconstruction
- Results with 500fb-1
d(sigxBR)/(sigxBR)
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bb: 0.45%
cc: 4.4%
gg: 3.2%
WW*:4.2%
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- H->WW* analysis
Pol=(+0.8,-0.2)
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bb: 1.6%
cc: 17.3%
gg: 13.8%
WW*:10.1%
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Combined results: (500eL+500eR)
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bb: 0.43%
cc: 4.3%
gg: 3.1%
WW*:2.1%
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- ZH followed by H->WW* @ 250GeV (mh=120GeV)
eLpR combination done
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WW*: 8.1% (-0.8,+0.3)
WW*: 6.8% (+0.8,-0.3)
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Next Step:
- Invisible decay
- qqH->qqWW*->6jets
- mh=125GeV
- H->ZZ*

2) ZH analysis: rare modes, H->mu+mu- (C.Calancha)
Status:
- Z->H->mu+mu- @ Ecm=1TeV
BR(H->mu+mu-)=0.000221: very tiny
Signal:
45 events with 500fb-1 (-0.8,+0.2)
4 events with 500fb-1 (+0.8,-0.2)
Main BG: ZZ, WW -> vvmu+mu-
Now includes AA Hadron BG
- Fitting BG to create a BG template and perform toy MC to carry out
many pseudo experiments.
- Fit the mass distributions from the pseudo experiments
--> delta (sigma x BR) / sigma x BR = 31% (-0.8,+0.2) with 500fb-1
Next step:
- H->AA
- H->AZ

3) ZH analysis: H->tau+tau- (S.Kawada)
Status:
- Z->H->tau+tau- @ Ecm=250GeV 250fb^-1, P(e+,e-)=(+0.3,-0.8) (mh=120GeV)
BF(tau+tau-)=8.0% (Pythia)
- Full simulation study (w/ LOI samples)
- Z->ll (l=e,mu)
Significance = 7.4 sigma (Z->ee)
Significance = 8.5 sigma (Z->mumu)
- Z->qq
Reconstruct Higgs mass using collinear approximation
--> Significance = 25.6 sigma
- Combined results:
Significance = 28.0 sigma
--> delta (sigxBR)/(sigxBR) = 3.6%
--> 4.6% (for mh=125GeV LHC-tuned BR)
Next step:
- Z->vv
- WW-fusion

4) TTH Subgroup (T.Tanabe)
Status:
- Working on to full simulation for Ecm=1TeV, mh=125GeV, mt=175GeV
500fb-1 eLpR(-0.8,+0.2) + 500fb-1 eRpL(+0.8,-0.2)
- BG: ttZ, ttg* (g*->bbbar), tt
+ AA->hadron BG (new)
--> removed by kt-algorithm
- Results with BDT analysis:
l+6J --> 8.4-sigma
8J --> 7.9-sigma
--> 11.5 sigma --> delta gt/gt = 4.5% (delta y/y = 0.52 x delta sig/sig)
- ttZ problem:
Fast simulation result was an over-estimate due to the old QCD correction table.
Next Step:
- Combine ILD + SiD --> publication
- Study systematic errors

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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 milestones
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*) Meeting Schedule:
Next general meeting (2013/03/16 10:30) : Conf.ID: 788
*) Post DBD Studies:
Exp:
- mh=125GeV for 250GeV, and 500GeV analyses.
- h->ZZ*, AA, ZA for both ZH and vvH
- Further improvement of BR measurements
- Further improvement of self-coupling measurements
- Studies of systematic errors
Th:
- To what precision do we need to measure Higgs properties?
- How well do we expect to control theory uncertainties for both LHC and ILC?
- Comparison of LHC and ILC reach in a generic model space

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

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