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Date/Time: 10:30~17:30 JST, June 14th, 2021
Place: Online Web Meeting
Official Language: English
Zoom Connection: (changed)
https://cern.zoom.us/j/63020693078?pwd=MkcyTE9UVWpBWnRTd3ZKdWZzN3lhUT09
TV meeting(via CERN Zoom):
1. 188.184.85.92 or 188.184.89.188
2. meeting ID: 630 2069 3078
the 72nd general physics meeting of ILC physics subgroup
— participants:
Yumi Aoki (Sokendai)
Takahiro Mizuno (Sokendai)
Keita Yumino (Sokendai)
Keisuke Fujii (KEK)
Daniel Jeans (KEK)
Tomohisa Ogawa (KEK)
Key Hidaka (Gagugei)
Yu Kato (Tokyo)
Junping Tian (Tokyo)
Jurina Nakajima (Sokendai)
Wataru Ootani (Tokyo)
Taikan Suehara (Kyushu)
Mami Kuhara (Kyushu)
Tomoki Onoe (Kyushu)
Yuki Ueda (Seikei)
Arindam Das (Hokaido)
********Morning Session************
— openning remark (K. Fujii)
- Pre-Lab proposal submitted together document from JAHEP
- Budget request not yet ready to be approved
- Moving forward: Snowmass resumed; ILCX 2021 in October, hybrid or fully online
- Political environment stays good
- KEK PIP process startedJ
- AHEP ILC steering panel established: outreach; X+ILC talks in universities (7 times)
- Message from IDT chair: MEXT will setup a panel to review submitted ILC documents,
hopefully to completed before end of this calendar year; we community should provide as support as possible
- WG3-PHYS meeting on July 16; WG3-SOFT tutorial
— Probing a minimal U(1) model at future e+e- via fermion pair production (A. Das)
- arXiv:2104.10902
- Missing in SM: tiny neutrino mass; relic abundance of dark matter;
- Energy frontier / Intensity / Cosmic
- U(1) model
extra singlet scalar phi; U(1) charge combination of hyper charge and B-L;
anomaly cancellation condition; dark matter candidate, right handed neutrino
- U(1) breaking gives Z’ mass; neutrino mass with seesaw mechanism
- Z’ couples to left / right handed fermion differently
- choices of x_H keeping x_phi = 1
- new particles: Z’, N_R, Phi
- limits on model parameters
Q: LHC limit comparison (including HL-LHC)
Q: dominant contribution
- 4-parameters: x_H, x_Phi, g’, mZ’
Q: preferred value of g’
A/C: free parameter, below perturbative bound, < 1 for mZ’ ~ 7.5 TeV.
Q: possible origin of U(1)_X
A: GUT SU(5)
*******Lunch Break**********
— e+e- —> gamma Higgs (Y. Aoki)
- Motivation: new physics in HAZ and HAA couplings (A for photon)
- Cross section peaks at around 250 GeV; significant destructive interference between box W diagram and top triangle diagram; sigma ~ 0.2 fb, challenging analysis
- EFT: two effective couplings HAZ, HAA; HAA can be constrained well at HL-LHC using BR(H—>AA)
- Full simulation
- Pre-selection: Photon ID (Pandora); E_A > 50 GeV; recovery of split clusters
- H—>bb channel
b-tag cut: bmax1 > 0.77
MVA: E_A, mh_bb (angular method)
significance: 0.26 for e_L
- H—>WW*->gamma + l + 2-jet + missing
C: add a step of isolated lepton finder
significance: 0.31 / 0.04 for e_L/R
- MC uncertainty
- qq background breakdown: dominated by bb; little room for better flavor tagging
- combined upper limit: sigma_L < 1.8fb, sigma_R < 0.5 fb
- interpretation in EFT for bounds on HAZ coupling
Q: lower bound from positivity?
C: upper bound
C: two-parameter bounds, independent constraint on HAA
A: yes, will do
— Tau reconstruction in e+e- -> tau tau (K. Yumino)
- highest lepton; only lepton to hadrons; requires neutrino reconstructed for maximum sensitivity to tau spin
- A_tau can be measured with A_FB and A_e (from beam polarization)
- A_tau can be also measured with tau polarization as a function of tau polar angle
- previous study by D. Jeans et al relies on track impact parameters
- this study uses only kinematic constraints with known m_tau, E_tau; Cone method, tau momentum should be on a cone around visible product, cone size constrained; solutions are at the intersection of two cones (after one cone flipped)
- restrict signal without hard ISR: m_tautau > 240 GeV
- no solution when no intersection
- generate event w/o ISR & beam energy spread
everything MC, still no solution ~5% events, why?
A: ISR, beam energy spread
- next step to investigate how impact parameter can help
C: acceptance should be defined based on MC polarimeter histograms before and after selection
Q: P11, both tau plotted?
A: Yes
Q: how are two neutrino momenta determined?
A: explained in P7
C: need to study how the methods are affected by detector effects, e.g. allowed cone sizes should be smeared by detector resolutions
— Exploring Right Handed Neutrinos at ILC (J. Nakajima)
- RHN: same sign leptons significantly reduce background
- Forgot to consider Br of N->eqq (assuming 100% for the following)
- Using Delphes fast simulation
- Invariant masses look good, but having some bias
- Charge mis-ID: using full sim background. Not negligible but not overwhelming.
Q Is g1' Z'NN coupling?
A yes
C g1' = 1 means xH = -1.2. Enhancement on RHN production occurs at the parameter.
B-L means xH = 0, where LEP2 limit is tight.
C Background statistics show 1% mistag rate of the charge, but it seems too high.
It should mainly come from pion contamination. Should check MC truth.
C Cut plots should be provided except cuts on the parameter concerned.
— Higgs exotic decay & kinematic fitting (Y. Kato)
- WIMP DM couples with scalar mediator phi
- b probability: using sum of four b-likeliness
- mumuH, H->bb is main background
- ~0.1% Br limit (90%CL) obtained at 15-60 GeV phi mass
- Kinematic fit - see some improvements
Q How to calculate significance?
A Combine significance of each bin
C Should not use Gaussian assumption to calculate significance because of low statistics.
C Fitting the distribution should be more reasonable
C Simple cut on the plot (with automatic tuning) is also good,
Å@but have to care that we don't know the true mass?
C OK if we assume cuts to optimize at each mass.
C Using 2 higher b-tag values should not be good. 2 lower b-tags should work.
Q Is h -> ZZ, ZZ -> 4b dominant?
A 2nd dominant. ZZ decay not checked.
C Should reduce h->bb if using y-value to separate 4-jet and 2-jet.
— Discussions (all participants)
- next general physics meeting, August 25, Wednesday from 10:30am
- meeting announcement to be circulated to theorist mailing list