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Date/Time: 10:30~17:30 JST, September 5, 2015
Place: Room 425, Building No.3, KEK
Official Language: English
Video Conference ID: 603 (KEK MCU2)
Fuze connection: http://fuze.me/30410114
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A Summary of The 43nd General Meeting of the ILC Physics Subgroup
September 5, 2015 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
Present at KEK:
A.Ishikawa (Tohoku)
K.Fujii (KEK)
J.Tian (KEK)
J.Yan (KEK)
T.Ogawa (Sokendai)
K.Hidaka (Tokyo gakugei)
H.Ono (NDU)
Remote connection:
K.Ikematsu (Saga)
Y.Sudo (Kyushu)
0) Opening comments (K.Fujii)
1) Leptonic recoil mass analysis (Jacqulline Yan)
Status:
Improvements since the last meeting:
Evis cut
TMVA
Cross section measurements (combined with invisible cross section)
Ecm=250GeV
(-0.8,+0.3) 2.65% 34.2MeV
(+0.8,-0.3) 2.95% 39.2MeV
Ecm=350GeV
(-0.8,+0.3) 3.27% 92MeV
(+0.8,-0.3) 3.63% 105MeV
Ecm=500GeV
(-0.8,+0.3) 5.29% 500MeV
(+0.8,-0.3) 5.34% 586MeV
Investigation of mode dependence
Major problem turned out to be coming from wrong lepton pairing for H->ZZ*, WW*.
-> Chi2 method to select the correct pair.
-> Improved but not sufficiently.
-> The bias is nevertheless very small already for the SM-like branching ratios,
negligible even for H20.
Next Step:
- TMVA for selecting best pair.
- increase MC statistics.
- publication.
- systematic error due to beam spectrum.
2) Anomalous HVV couplings (Tomohisa Ogawa)
Status:
Anomalous HVV couplings:
SM-like, FF, FFtilde
Zh production:
Observables:
- production angle of Z
- delta phi (angle btw production and decay planes of Z)
- sigma_Zh
Update since the last meeting:
Fit phi and theta simultaneously.
Studied the Ecm dependence.
-> Sensitivity to anomalous coupling, in particular for costh, seems to
increase with Ecm dramatically.
Updated the analysis to separate the sensitivity coming from shape and that
from the total cross section.
Optimize the cuts to maximize the overall signal significance, while keeping the
(phi and costh) acceptance as flat as possible.
Updated the analysis to separate the sensitivity coming from shape and that
from the total cross section. -> new chi2 definition.
-> New contours. -> delta b ~ 0.01, delta btild ~ 0.01 with 500fb-1 @ 500GeV.
Next Step:
- Do other channels and add them to the chi2.
3) Top Yukawa coupling study at 500 GeV (Yuji Sudo)
Status:
500GeV (500fb-1), (-0.8,+0.3)
Updates:
new 6f samples
jet pairing by maximum likelihood
-> 10% improvement for b-pair from the Higgs.
Results: (significance)
(-0.8,+0.3) 2.01 (8j)
1.91 (l6j)
0.88 (2l2j)
(+0.8,-0.3) 1.36 (8j)
1.30 (l6j)
0.61 (2l2j)
The numbers are for cut-based selection.
Next step:
- Resolve the problem with the cross section estimates.
— optimize the selection.
4) Higgs BR study (Hiroaki Ono)
Status:
500GeV analysis just started.
planning to do template smoothing, variable bin widths to improve template stability.
Next Step:
- investigate more on template stability.
- TMVA.
- Summarize 250 analysis.
5) Tools (Junping Tian)
Status:
Isolated lepton tagging algorithms
new MVA-based algorithm outperforms the old ones: Cone and LAL significantly.
-> 0.02% BG efficiency at 90% signal efficiency.
-> new training sample -> another factor of 2 for muons.
-> Investigating the source of mis-tagging.
most dominant was mus from jets.
2nd dominant was found to be Kaons (K to muv decay in CAL).
For electrons 2nd dominant was pions (charge exchange in CAL).
New jet-clustering
Potential impact on HHH coupling:
40% if we have perfect color-singlet clustering.
We know that Durham is correct till 20 mini-jets.
idea is to assign at this level the probability using parton shower PDF.
-> there seems to be correlation between these 20 mini-jets and partons
to certain extent.
Strategy is to follow all the history of parton showering.
Next Step:
- construct likelihood for parton showering
6) Discussions: all
Our highest priority is to prepare a short summary of BSM prospects at ILC.
Given the short time scale, we need to rely on existing studies.
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The slides shown at the meeting is available from
https://agenda.linearcollider.org/event/6793/
see them for details.
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*) Meeting Schedule:
Next general meeting (2015/10/24 10:30) : Conf.ID: 667
Working group web page:
http://www-jlc.kek.jp/jlc/en/subg/physics