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The 68th General Meeting of ILC Physics Subgroup

→ Asia/Tokyo
Keisuke Fujii (IPNS, KEK)
Description

Date/Time: 10:30~17:30 JST, November 11th, 2020

Place: Online Web Meeting

Official Language: English

 

Zoom Connection:

https://cern.zoom.us/j/93257269672?pwd=WHNFUDhjSmYrQXlWWlVwVmw0Nk9QQT09

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 68th General Meeting of the ILC Physics Subgroup
November 11, 2020 (Wednesday) held fully virtually because of COVID19
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0) Attendants:
R.Yonamine  (Tohoku)
Y.Aoki      (KEK/Sokendai)
K.Fujii     (KEK)
D.Jeans     (KEK)
A.Miyamoto  (KEK)
T.Mizuno    (KEK/Sokendai)
J.Nakajima  (KEK/Sokendai)
J.Tian      (Tokyo)
K.Hidaka    (Tokyo gakugei)
M.Kuhara    (Kyushu)
M.Kurata    (Kyushu)
T.Suehara   (Kyushu)
K.Inami
K.Ma        


0) Opening comments (K.Fujii)

1) e+e- -> tau+ tau- (Keita Yumino)
cancelled.

2) Deep Jet Clustering (Masakazu Kurata)
Status:
- Tool: Keras & Tensorflow backend
Convolutional NN applied to 9 64x64-pixel images
 (E, Q, D0sig. Z0sig, Ecal, Hcal, direction vector)
3 units for each of Encoder/Decoder 
 Application to ZHH->(qq)(bb)(bb) (q=u,d,s):
For the moment ignore color singlet.
            (2jet clustering by Durham for each color singlet)
            cross entropy L = (1/n) sum y_i log P_j
-> pseudo-labeling
     Perfect Durham clustering is not always best for CNN.
-> data cleansing
       Use 230000 events for training (90% for training, 10% for validation)
and compare confusion matrices for Durham and CNN
-> 1st 3 jets start to improve, last 3 bit worse
Next Step:
- Try to improve further.
 C: look at performance for clean 6-jet events without hard gluon emission.


3) e+e- -> Z gamma (Takahiro Mizuno)
Status:
- Used sample: 250 GeV DBD
- Kinematic reconstruction of jet energy using
 Method 3: consider ISR, use angles and mj1, mj2 as inputs 
    in full 4-momentum conservation
- Looked at JER as a function of two angles (phi/theta), energy, flavor,
 by fitting (E_J - E_MC)/E_MC with Gaus(core) + Gaus(base)+exponential
 and using the mean of the core for calibration.
-> for M3, the bias is of O(10^-4) or less.
Next Step:
- look at 2d dependences (E, theta)
 C: look at the charged particle fraction dependence


4) e+e- -> gamma H @ 250GeV (Yumi Aoki)
Status:
   sigma(Hgamma) = 0.2fb in SM.
- gamma H -> gamma (bb):
   Major Bkg: gamma Z -> gamma (bb)
-> significance : 0.36 for 0.9ab^-1 (eLpR)
- gamma H -> gamma (WW*) -> gamma + 1 lepton + 2 jets:
   Major Bkg: WW (gamma)  
   With TMVA(BDT)
-> significance : 0.27 for 0.9ab^-1 (eLpR)
- Combined limits on zeta_AZ
-0.0082 < zeta_AZ < 0.0082
- Checked the Bkg MC statisticas
- Checked the acceptance flatness with and without theta_gamma in MVA.
-> acceptance seems rather flat if theta is not included.
Next Step:
- Check the acceptance with the new sample
- Do eRpL case.
- Understand the role of this measurement in the BSM model tests and 
 in the global EFT analysis.



  -- Lunch Break --



5) LGAD simulation (Mami Kuhara)
Status:
- LGAD (Low Gain Avalanche Detector)
timing resolution 26ps (ATLAS, for 120 GeV pions)
- Simulation
E=1,2,5,10 GeV pi+/K+
<TOF> ~ 6ns for IP to ECAL front face
-> found the mass peak > 0.14 GeV for pi+
-> similar shift seen also for K+
-> calculating average TOF didn't help, need more investigation.
Next Step:
- Estimate resolution and PID combining LGAD and ECAL
- Make LGAD prototype and simulation
- Investigate the origin of the tail.
 Q: What about averaging time instead of mass?


6) Probing the quark flavor structure of New Physics by measuring the branching ratio of decays h(125) -> b dbar/sbar and bbar d/s (Keisho Hidaka)
- LHC limits on CLFV
BR(h->mu tau) < 0.28% @ 95%CL
BR(h->e tau) < 0.47% @ 95%CL
       while in SUSY inverse seesaw models a % level CLFV decay BR possible
- QFV at ILC?
BR(h->bs) can be as large as 0.17% in MSSM with large ss and sb mixing
No full simulation so far. -> One Snowmass target!
 Q: How important to separate s from d?
-> More information about BSM can be extracted if we can distinguish s from d.
 Q: Is there FCNC Z decay expected from the same mechanism?
-> Not studied yet.
 Q: Any parameter region left after CLFV search at HL-LHC?
-> Hopefully.


7) Discussions
7-1) Snowmass LoI presentations
- e+e- -> Z gamma (A_LR): TM (JT, KF): done
- e+e- -> H gamma: YA (JT, KF) (Mawatari): not yet
- e+e- -> tau+ tau-: KY (DJ, TS): done
- Higgs CP: DJ : Graham made a presentation
- RHN: RY (Nob Okada made presentation) 
- H->bs: KH (theory): not yet
- ttbar: YO (RP): not yet?
- ttbar (threshold): Warsaw Student (FZ)
- running b mass: Seidai Tairafune (MV): not yet?
- ZHH (Vertex Finding, Jet Clustering, MELA): MK, KI (+computing?): not yet?
- 2f final states: TS: done
 Ideas to expand the community:
 - Prioritize the 90 questions in the Snowmass study questions.
 - One invited (theory/experiment) talk per meeting.

----------------------------------------------------------
The slides shown at the meeting is available from
https://agenda.linearcollider.org/event/8966/
See them for details.
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*) Meeting Schedule:
 Next general meeting: 2021/02/10 (Web) 10:30)


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

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