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Date/Time: 10:30~17:30 JST, March 9th, 2020
Place: Online Web Meeting
Official Language: English
Zoom Connection:
https://cern.zoom.us/j/64597061826?pwd=N2lXMmQwWUxwVGQ1aTc0WnV4OVl0Zz09
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 70th General Meeting of the ILC Physics Subgroup
March 9, 2021 (Wednesday) held fully virtually because of COVID19
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0) Attendants:
S.Tairafune (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.Suehara (Kyushu)
0) Opening comments (K.Fujii)
1) e+e- -> Z gamma: JES study (Takahiro Mizuno)
- JES study has never been presented at previous LCWS series.
Photon selection:
M2j < 125 GeV && Evis > 200 GeV
cos(theta_jet.gamma)<0.95 for both jets
-> correct photon fraction = 99.5%
Kinematical reconstruction of JE:
using theta, phi, Mj for 2 jets (8 variables) as inputs
to determine p_j, p_gamma, p_ISR (4 variables)
JES calibration:
Fit the kinematically reconstructed delta E distributions with a double gaussian
and decide the calibration factor to 10^-4 accuracy.
2) e+e- -> tau+ tau- (Keita Yumino)
Status:
- Tau polarization study using cone method and MC truth.
-> found reasonable agreement between MC truth polarimeter value and the one
from the cone method for both pi nu and rho nu decays.
Next Step:
- Repeat this at various levels of cheating.
- Think about new physics interactions that affect this process.
3) RHN (Jurina Nakajima)
Status:
- Signal channel
e+e- -> NN -> eW eW (same sign leptons, BR~36%)
- Set 4 benchmark points consistent with the current limits and generated
RHN pair production events with Whizard.
- Study event selection
M_W problem solved by inserting a W-resonance as an intermediate state
to pass to Whizard.
Next Step:
- Study potential backgrounds.
-- Lunch Break --
4) e+e- -> gamma H @ 250GeV (Yumi Aoki)
Status:
sigma(Hgamma) = 0.2fb in SM.
- Results for new SM sample (using proper 1-loop amplitudes)
- gamma H -> gamma (bb):
Major Bkg: gamma Z -> gamma (bb)
-> significance : 0.29 for 0.9ab^-1 (eLpR)
- gamma H -> gamma (WW*) -> gamma + 1 lepton + 2 jets:
Major Bkg: WW (gamma)
-> significance : 0.26 for 0.9ab^-1 (eLpR)
Checked Bkg statistics.
Next Step:
- Do eRpL case.
- Understand the role of this measurement in the BSM model tests and
in the global EFT analysis.
5) b mass study with e+e- -> bb (Seidai Tairafune)
Status:
- Motivation and method
m_b(MSbar) runs differently depending on what is in the loop.
Use m_b dependence of R_3 (3-jet fraction) to measure m_b.
- MC set
new 250 GeV sample
- Event selection
Bkg: radiative return to Z, WW, ZZ, ZH
- veto energetic gamma (E_gamma > 50 GeV)
- do forced 2 jet clustering and require Thrust > 0.85
- Plot R^{bl}_3(y)
-> found R^{bl}_3(y_c) > 1, meaning that b quarks radiate a gluon more frequently
than light quarks unlike naive expectation.
- Estimated m_b error
for m_b = 2.75 GeV, delta R_3^{bl} = 0.996,
-> delta m_b ~ 1 GeV @ 250 GeV
-> delta m_b ~ 0.1 GeV @ Giga-Z
C: You should look at y_c < 0.001, where you you expect m_b-dependence.
High y_c region has no sensitivity to m_b.
6) 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 t_i log y_j
-> pseudo-labeling (reassignment of color to minimize L)
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 (correlation)
New: Multi Center
to recover splitting jets.
-> now training so no result yet.
C: Maybe it is difficult for AI to invent QCD.
Next Step:
- Try to improve further.
C: look at performance for clean 6-jet events without hard gluon emission.
7) Discussions
7-1) JPS Meeting
- e+e- -> Z gamma (A_LR): Takahiro Mizuno
- e+e- -> tau+ tau-: Keita Yumino
- e+e- -> N N: Jurina Nakajima
- e+e- -> b b: Seidai Tairafune
7-2) LCWS2021
- e+e- -> Z gamma (A_LR): Takahiro Mizuno
- e+e- -> H gamma: Yumi Aoki
- e+e- -> tau+ tau-: Keita Yumino
- e+e- -> N N: Jurina Tairafune
- e+e- -> b b: Seidai Tairafune
- Kinematic fitting : Yu Kato
- NN vertex finding : Kiichi Goto
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/9134/
See them for details.
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*) Meeting Schedule:
Next general meeting: 2021/05/12 (Wed) 10:30)
Working group web page:
http://www-jlc.kek.jp/jlc/en/subg/physics