20080906-e

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A Summary of The 23rd General Meeting of the ILC Physics Subgroup
Nov.5, 2011 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
R.Settles (MPI)
A.Ishikawa (Tohoku)

A.Yamamoto (Tohoku)
T.Tanabe (Tokyo)
T.Suehara (Tokyo)
R.Katayama (Tokyo)
H.Ono (NDU)

S.Kawada (Hiroshima)
Y.Okada (KEK)
J.Tian (KEK)
T.Yamada (Sokendai)
R.Yonamine (Sokendai)
P.Posh (Sokendai)
D.Harada (KEK)
K.Fujii (KEK)

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Opening Comments
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[A] Symmetry breaking & mass generation
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1) ZH subgroup
1-1) ZH analysis (Reported by H.Ono)
Status:
- Setup: mh=120GeV,
250fb^-1@250 and @350GeV, Pol(e+,e-)=(+30%,-80%)
- BR(H->bb,cc,gg) -> preparing 1st draft for publication.
delta BR(bb)/BR(bb) = 2.7% (250GeV)
delta BR(cc)/BR(cc) = 8.1% (250GeV)
delta BR(gg)/BR(gg) = 9.0% (250GeV)
- Updated recoil mass plots @250GeV for mh=120, 130, 140GeV.
--> seems much nicer than the old GLD plot.
- New projects: include other decay modes such as H->WW*, …,
taking into account LHC results, focus on 115 < mh < 140 GeV
(Takubo: delta BR(WW*)/BR(WW*) = 15.7% (250GeV): 4J only)
- nnH @ 1TeV strategy
Next Step:
- Publication.
- Full simulation for different decay modes, masses
- nnH @ 1TeV
--> WL, ZL, H as new particles to be probed by high virtuality probe.
C: we need BR(H->tau+tau-, ZZ*, ZA, AA).

2) ZHH subgroup (Reported by J.Tian)
2-1) ZHH @ 500GeV
Status:
- Previous analysis
mH=120GeV, 2ab^-1
--> excess significance: 3.9 sigma
--> delta sigma_ZHH = 0.22+/-0.07fb (32%)
--> delta lambda/lambda = 57% (= 1.8 x delta sigma/sigma)
--> Not enough
- Temporary goal: a factor of 2 improvement!
- Possible places for the future improvements
jet clustering, b-tagging, jet paring, lepton ID
--> In order to estimate the limit we can achieve, develop cheaters
ISRTaggerProcessor
ColorSingletTaggerProcessor
SatoruJetFinderWithCheatProcessor
- Findings:
There are a significant number of photons associated with isolated leptons (FSR).
With cheated jet clustering, the mass separation became very good.
--> ZZZ, ZZH BG could be more cleanly separated.
--> llbbbb significance could be improved from 2.1sigma to 3.9sigma by cheating!!
Next Step:
- Continue cheating for other modes.
- Publication of the current results
- nnHH @ 1TeV
- different mH

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2) AA->HH Group
2-1) Experiment (Reported by Kawada)
Status:
- Increased the BG statistics and use different samples for NN training.
--> Signal significance dropped from 1.17 to 0.7 for 5 yeas running (TESLA optimistic).
--> With cheated jet clustering, the significance is 4.7.
Next step:
- Write a paper.
- Improve b-tagging & jet-clustering.
C: Higher Ecm might be more advantageous in terms of S/B ratio.
C: Check what happens to sensitivity plot if eta_BG is nonzero and eta_S is less than 1.

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3) TTH Subgroup (Reported by R.Yonamine)
Status:
- Moved on to full simulation for Ecm=500GeV, mh=120GeV, mt=175GeV
- ttH, ttg* MC samples: produced. ttZ: not yet.
- Now investigating lepton ID.
Next Step:
- ttZ data production.
- parameter optimization for lepton ID.
- cheated jet clustering.
- 1TeV
- mH=140GeV using H->WW*

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[B] New physics
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1) Higgs Portal (Reported by A.Yamamoto)
Setup:
By definition, Higgs portal DM only interacts with Higgs.
Signal: e+e- -> ZH -> ffbar (DM DM): 15fb @ 250GeV.
BGs: ZZ, nnZ, WW, enW, eeZ, ZH
Status:
- Event Selection
isolated lepton cut: effective to reprove WW BG.
forward e+/- cut to reject enW, eeZ BG.
Z mass cut
- Preliminary results
-->There is some inconsistency between the present analysis and that of Honda.
BGs are still high. --> Need to improve event selection.
Next Step:
- Optimize event selection.
- Try right-handed polarization.
- Do the same at 500GeV.
- t-channel H production at 1TeV.
C: Check the cross sections with other tools such as Madgraph.
C: Check the h-DM-DM Lagrangian.

2) Very light gravitino (Reported by R.Katayama)
Setup:
m_\tilde{G} = <F>/Mpl/3^{1/2} with 1/<F> ~ 1/(Mpl m_{3/2})
-> directly connected to the SUSY breaking scale.
m_\tilde{G} = O(1)-O(10)eV
-> interesting allowed region
hep-ph/9503210
ILC signal:
NLSP=stau
ctau ~ 100 microns (m_LSP=6.5eV, m_NLSP=120GeV)
(tau ~ 48pi M_pl^2 m_\tilde{G}^2 / m_stau^5)
Want to measure ctau, from which m_gravitino is extractable
given the stau mass is measured beforehand by E_tau, etc.
Simulation & Analysis:
Measure the deviation of the impact parameters for the tau decay products
from the SM prediction.
Status:
- A signal generator prepared.
- BG: tau+tau-, W+W-, Z0Z0, two-photon tau+tau-.
- Event selection using full sim. samples
--> Look at impact parameter distributions for tau+tau- & mu+mu- BG.
--> Cuts on Evis, Pt, acoplanarity, angle/Evis: essential to suppress AA->tau+tau-
--> AA->tau+tau- :suppressed from O(10^9) to 0.
- Stau mass reconstruction from end point.
--> delta m /m = 1.1 x 10^-2
--> Effect of non-Gaussian Ebeam spread?
- Life time fit
--> delta tau /tau = 1.4 x 10^-2
- Gravitino mass from tau and m measurements:
--> delta m_\tilde{G}/m_\tilde{G} = 3 x 10^-2
Next Step:
- More statistics for two-photon and Bhabha BGs.
- Study the mass extraction from threshold scan.
- Different stau mass and life time.
C: First make sure it is stau then make sure it decays into non-standard LSP.
Q: What is the range of life time to which this analysis method can be applied?

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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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*) Higgs WG
1st meeting: Nov.11 (fri) 16:00 : Conf. ID: 633.
Meeting Schedule:
*) ACFA2012 Meeting: April 23-26, Degu.
*) LCWS2012 Meeting: Oct 22-26, Arlington, Texas.
Next general meeting (2012/01/28 10:30) : Conf.ID: 863

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

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