20080906-e

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A Summary of The 32nd General Meeting of the ILC Physics Subgroup
June 22, 2013 (Sat) at Room 425, Building 3, KEK
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Attendants:
Present at KEK:
T.Tanabe (Tokyo)
T.Suehara (Tohoku)
T.Horiguchi (Tohoku)
C.Calancha (KEK)
H.Ono (NDU)
S.Watanuki (Tohoku)
K.Tsumura (Nagoya)
J.Tian (KEK)
S.Kawada (Hiroshima)
M.Kurata (Tokyo)
A.Ishikawa (Tohoku)
K.Fujii (KEK)

0) Opening comments (K.Fujii)

1) Higgs BR Studies for mh=125GeV at 250, 350GeV (H.Ono)
Status:
- New sample now available with new beam parameters
new mh = 125GeV
new BR : LHC Higgs XSWG
Ecm : 250,350,(500),
new detector model: ILD_01_v05
new software: ilcsoft v01-16
new flavor tag: LCFIPlus
- #events very similar to the LoI case because of new beam parameters in spite of the Higgs mass change to 125GeV.
- two-photon BG negligible at 250GeV -> Will not use the anti-KT jet clustering at 250GeV
- Event selection
vvh: cut values are fixed, now testing LCFIPlus performance, etc.
--> 6q500 tuning seems to be the best among qq91, qq250, and 6q500.
- Flavor template fitting
e.g.) Z->vv
delta sigma(zh)xBR(h->bb) / sigma(Zh)xBR(h->bb) consistent with extrapolation.
--> need to add likelihood cuts to improve h->cc and gg results.
Next Step:
- Complete BR studies for mh=125GeV in time for the Snowmass white paper.
- Investigate systematic uncertainties
C: Apply E_pfo cut first and optimize the cuts, then the electron ID might be further improved.

2) ZH: H->tau tau for mh=125GeV at 500 GeV (S.Kawada)
Status:
- Simulation conditions
mh=125GeV, sqrt(s)=500GeV, 500fb-1, pol=(-0.8,+0.3)
BR(h->tau tau)=6.32%
- Event selection (now concentrating on vvh)
13.1sigma --> 7.6%
--> Much better than our very rough guesstimate in DBD!
Next Step:
- Include 3f and aa_2f
- More optimization
- Include qqh

3) Higgs->AA at 500GeV (C.Calancha)
Status:
- New sample with mh=125GeV
- Expected number of signal events:
Ecm=250GeV, 250fb-1 --> 160 events
Ecm=500GeV, 500fb-1 --> 292 events
- H->AA samples
regenerated with the correct lumi_linker files (21 for 250 and 22 for 500 GeV).
--> now working mostly on 500GeV vvh analysis.
- Event selection for vvh
mass resolution: 2.9 GeV after correction for splitting photons
250GeV -> ~1sigma significance
500GeV -> much better
Next Step:
- Upgrade lumi to 900fb-1 at 250GeV and 1100fb-1 at 500GeV.
- Increase BG statistics.
- Get results by the Snowmass E-frontier meeting.

4) hWW coupling at 500GeV (J.Tian)
Status:
- Event selection
For h->bb, anti-kt: R=1.5 seems optimum.
For h->WW*, simple minded anti-it is not satisfactory.
--> MVA based two-photon hadron BG rejection + Durham work better.
- Results
h->bb: delta (sigma x BR) / sigma x BR = 0.667% (DBD extrapolated: 0.661%)
h->WW*: delta (sigma x BR) / sigma x BR = 2.8% (DBD extrapolated: 2.6%)
- Discussion on luminosity upgrade and running scenarios
With the constraint of t250+t500 = 10years, optimized t250 for coupling precisions.
--> The 250GeV running alone is not the optimum!

5) Recoil mass measurement (S.Watanuki)
Status:
- Signal sample: mh=125GeV at Ecm=250 GeV with (P_e-,P_e+)=(-0.8,+0.3).
- Recoil mass:
delta mh = 80MeV
delta sigma / sigma = 5%
--> too large? --> Something is wrong.
Next Step:
- Check and improve the fit.
- Optimize the cuts.

6) Self-coupling 2: HH->bbWW* (M.Kurata)
Status:
- Soft-jet finding
gluon jets are expected to be wider than quark jets.
--> MVA to form soft-jet-likeliness
Combined results
--> 1.9 sigma significance as compared to previous 1.15 sigma.
Next Step:
- Improve analysis

7) Top pair threshold (T.Horiguchi)
Status:
MC simulations with
mt=174 GeV, 11 points with 10 fb-1 each from 340 to 350 GeV in 1 GeV step.
beam polarization: (-0.8,+0.3) (Last time it was (+0.8,-0.3)
BG: WW, ZZ, qqH
Event selection:
efficiency: 0.4 - 0.45, almost linear function of Ecm.
Sensitivity to top Yukawa coupling
delta yt / yt = 4.2%
--> expect 3% if l+4j included.
Extracted the luminosity spectrum which was convoluted with the theoretical cross section from Kiyo san.
Next Step:
- Evaluate error on yt by fitting
- Evaluate error on mt and Gamma_t by fitting
- More BG
- l+4j after Snowmass Seattle.

8) What if K_V is not equal to one? (K.Tsumura)

9) EWkino Scan (T.Tanabe)
Status:
- Trying to inputs the results to the Snowmass process as a part of
the ILC BSM whitepaper.
- The current limits
LEP: m_{\chi^\pm} > 90GeV
ISR-tagging technique used for \Delta m ~ O(1GeV)
LHC: ATLAS 20.7fb-1 (8TeV) 3 leptons + MET search
(assuming that bino LSP, \chi_1^\pm, \chi_2^0 are wino and degenerate)
- Setup
EWkinos are the only light SUSY particles.
- Outlook
Standard search for delta m being large.
For higgsino LSP or wino LSP scenarios, delta m becomes small and standard search strategy will not work.
M_recoil against ISR gamma (J.List) --> looks promising.
--> delta m < 1GeV
Next Step:
- Parameter scan and input the results to the Snowmass process.

10) H->Invisible (A.Ishikawa)
Status:
- Full simulation
Ecm=250GeV, mh=125GeV, Pol=(-0.8,+0.3), (+0.8,-0.3)
Official DBD samples
- Event selection
No isolated electrons
- New peaking BG: qqH, vvH
Next Step:
- Finish up the analysis for Snowmass.

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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 (2013/08/24 10:30) : Conf.ID: 919

*) Contributions to Snowmass Seattle:
Exp:
- Tanabe: EWkino
- Horiguchi: ttbar
- Kawada: h->tatau
- Tino: h->gamma gamma
- Akimasa: TBC

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

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