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Date/Time: 10:30~17:30 JST, February 10th, 2020
Place: Online Web Meeting
Official Language: English
Zoom Connection:
https://cern.zoom.us/j/98515664736
TV meeting(via CERN Zoom):
1. 188.184.85.92 or 188.184.89.188
2. meeting ID: 966 4733 5143
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Summary of The 69th General Meeting of the ILC Physics Subgroup
February 10, 2021 (Wednesday) held fully virtually because of COVID19
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0) Attendants:
Y.Okugawa (Tohoku)
Y.Aoki (KEK/Sokendai)
K.Yumino (KEK/Sokendai)
K.Fujii (KEK)
D.Jeans (KEK)
A.Miyamoto (KEK)
T.Mizuno (KEK/Sokendai)
J.Nakajima (KEK/Sokendai)
J.Tian (Tokyo)
M.Kurata (Tokyo)
K.Hidaka (Tokyo gakugei)
T.Tanabe (IPMU)
K.Goto (Kyushu)
0) Opening comments (K.Fujii)
1) e+e- -> gamma H @ 250GeV (Yumi Aoki)
Status:
sigma(Hgamma) = 0.2fb in SM.
- Modified the selection to assure flat acceptance.
- gamma H -> gamma (bb):
Major Bkg: gamma Z -> gamma (bb)
-> significance : 0.31 for 0.9ab^-1 (eLpR)
- gamma H -> gamma (WW*) -> gamma + 1 lepton + 2 jets:
Major Bkg: WW (gamma)
With TMVA(BDT)
-> significance : 0.24 for 0.9ab^-1 (eLpR)
Q: The new efficiency for the WW* channel seems too low?
A: Will check.
Next Step:
- Replace the signal sample with the new SM.
- Check the Bkg statistics with the new cuts.
- Do eRpL case.
- Understand the role of this measurement in the BSM model tests and
in the global EFT analysis.
2) e+e- -> Z gamma (Takahiro Mizuno)
Status:
- Just started physics analysis using DBD samples.
At ILC 90 M Zgamma events expected, significantly larger that SLC/LEP.
Now looking at M_z distribution reconstructed from jet angles.
Next Step:
- Move to new 250 GeV samples.
- Look at various distributions for the signal and backgrounds.
C: Fist look at MC truth distributions to compare the DBD and the new samples.
3) e+e- -> tau+ tau- (Keita Yumino)
Status:
- Collinear approximation didn't work well.
-> Decided to try a new method to reconstruct tau directions assuming tau+ and tau-
are back to back and there are only one neutrino from each tau decay.
-> Reconstruction accuracy seems better for events with leptonic decays than those with
only hadronic decays unlike expectation.
Next Step:
- Investigate the problem above.
C: Better first look at events for which the method should work, i.e., those with only
pi+nu decays and without initial state radiation or beamstrahlung. Try the method
also with MC truth to avoid effects of finite detector resolution.
C: Check reconstruction efficiency.
-- Lunch Break --
4) RHN (Jurina Nakajima)
Status:
- Generated 5k e+e- -> NN -> eW eW (same sign leptons, BR~36%) events for 4 sets of model
parameters:
MN=100,200GeV x MZ'=7,3TeV
at Ecm=500GeV using LCIO Delphes miniDST.
Q: Why is the BR ~36%?
A: The BR includes the effect of the N to nu_e + Z decay.
Q: Are the model parameters still allowed?
A: Yes.
Q: Why do the W mass distributions look different for different parameter sets?
C: Try perfect jet clustering.
C: Look also at the generator level MW distribution.
Next Step:
- Understand the MW distributions.
- Study potential backgrounds.
5) Discussions (conference talks)
5-1) JPS Meeting
- e+e- -> Z gamma (A_LR): TM
- e+e- -> tau+ tau-: KY
- e+e- -> N N: JN
5-2) LCWS2021
- e+e- -> Z gamma (A_LR): TM
- e+e- -> H gamma: YA
- e+e- -> tau+ tau-: KY
- e+e- -> N N: JN
We should discuss this next week at the regular weekly meeting with more participants.
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The slides shown at the meeting is available from
https://agenda.linearcollider.org/event/9086/
See them for details.
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*) Meeting Schedule:
Next general meeting: 2021/03/9 (Tue) 10:30)
Working group web page:
http://www-jlc.kek.jp/jlc/en/subg/physics