Date/Time: 10:30~17:30 JST, May 12th, 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 71st general physics meeting of ILC physics subgroup
— participants:
Yumi Aoki (Sokendai)
Takahiro Mizuno (Sokendai)
Keita Yumino (Sokendai)
Keisuke Fujii (KEK)
Daniel Jeans (KEK)
Akiya Miyamoto (KEK)
Tomohisa Ogawa (KEK)
Keisho Hidaka (Tokyo Gagugei)
Yu Kato (Tokyo)
Junping Tian (Tokyo)
Kei Yagyu (Osaka)
Kentaro Kawade (Shinshu)
Tomohiko Tanabe (Iwate)
Taikan Suehara (Kyushu)
Shusaku Tsumura (Kyushu)
Mami Kuhara (Kyushu)
Kiyotomo Kawagoe (Kyushu)
Tomoki Onoe (Kyushu)
********Morning Session************
— openning remark (K. Fujii)
- study 125 GeV Higgs is more important than ever
- IDT formed for Pre-Lab; Autumn workshop ILCX2021, 3 options for full online, in person or hybrid
- ILC realization: strong support from US, ESU, community
- IDT WG3 physics & detector meeting every two weeks
- Pre-Lab Proposal, under review by ICFA, to be submitted to MEXT later this month
- Snowmass white paper: 1st draft at ILCX 2021, arXiv January 2022, final August 2022; call contribution in particular to new sections, Fixed-target program, Long-term future of ILC Lab
- IDT WG3 Physics group kickoff meeting on May 27, participate and subscribe to mailing lists
— Recent top-quark measurements @ LHC (K. Kawade)
- most massive particle; couple with many BSM; precision test of pQCD / EWK; important background
- top-factory: tt x-sec ~ 832 pb, Run2 ~120M tt events, 90% gg fusion, 10% qq annihilation
- signatures: high-pT lepton / q-jet, MET, b-jet, boosted top
- tt x-sec meas. cleanest channel e-mu instead of e-e or mu-mu to avoid Z background;
b-tag efficiency is obtained from data, MC does not reproduce the correct efficiency;
2.4% total uncertainty, dominated already by sys., ~2% luminosity;
differential x-sec: some tension between MC & data, better modeling needed.
- top mass meas.: vacuum stability (with m_h ~ 0.2 GeV uncertainty LHC Run2);
MC mass - direct reconstruction from top decay;
pole mass - short distance mass, indirect meas. from cross section.
- MC mass: direct meas., Jet Energy Scale calibration crucial; using W boson mass to reduce JES;
semi-leptonic + hadronic: 172.26 +/- 0.07 (stat+JSF) +/- 0.62 (syst) GeV.
- pole mass: tt x-sec; sensitive to PDF, alpha_S, etc.; differential x-sec is better;
simultaneous fit to triple differential x-sec., N_jets, m_tt, y_tt;
result: 170.5 +/- 0.8 GeV
(C: N_jet as # other than from top, discrete variable, dN_j = 1)
(C: 170.5 seems not to be consistent with right plot?)
- running mass: probed up to m_tt ~1TeV, consistent with SM NLO
- top decay width: direct m_lb, 1.9 +/- 0.5 GeV
- top-Yukawa coupling ttH: one primary target, 5.8sigma @ Run 2, 6.3sigma Run 1&2
- rare top process: ttbb, tXq**, ttX**, tttt, FCNC; test SM
- ttZ, ttgamma, ttW, < 1 pb: more ttX than tt @ Tevatron; important for measuring top Electroweak couplings to Z, gamma; large sys. error?
- tttt: ~12 fb, ttH CP, enhancement in many BSM; same-sign lepton channel or >= 3 leptons; 24 +7/-6 fb, ~ SM = 12.0 +/- 2.4 fb
- FCNC: 10^-14 in SM; upper limit ~ 10^-4; x4 improvement by HL-LHC
Q: how to convert MC mass to Pole mass?
A: relation not very clear, need to consult with theorist.
C: ILC can measure precisely pole mass or short distance mass by tt threshold scan
Q: b-tag efficiency, how precise? data vs MC?
A: extracted from data, MC doesn’t reproduce well.
Q: luminosity systematic error?
A: calibration by Van der Meer Scan, a method from 50 years ago; relying on forward detector; right now ~2% uncertainty; one limiting factor
C: measuring ratio of x-sec can cancel out luminosity sys.
Q: in differential x-sec meas., is there excess in high pT region?
A: no; seems over prediction in theory at high pT
Q: pole mass result on bottom right plot correct? 170.5 in the text?
A: not consistent here, need to check
Q: how about ATLAS on the pole mass?
A: 13 TeV results not published yet, resolution seems not better than CMS.
— Jet Energy Scale Calibration using e+e- -> gamma Z @ ILC by T. Mizuno
- JES is crucial for precision measurements
- e+e- -> gamma Z -> gamma + 2-jet: jet energy can be reconstructed using jet angles and kinematical constraints
- event selection: 1 isolated energetic photon > 50 GeV by Pandora photon ID; 2-jet Durham algorithm in LCFI+
- jet angular distribution: higher energy jet very forward, lower one is rather flat
- signal: E_gamma ~ 108 GeV, m_jj ~ 91 GeV
- reject events with wrong photon selection
- reconstruction method: input from jet masses, jet angles, photon angles; 4-momentum conservation; output jet energies, photon energy, extra ISR energy; select the best out of 8 solutions, closest to directly measured photon energy
- preliminary new results with new jet MC truth definition
- observed flavor dependence
Q: how is jet energy distributed?
A: page 5.
C: better to check energy dependence on jet reconstruction.
Q: why is there large asymmetric tail in the JER plot?
A: not known yet, likely related to under estimated MC truth, need further investigation
*******Lunch Break**********
— 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)
- no solution when no intersection
- preliminary results more or less reasonable, compared with various MC expectation;
- polarimeter vector: in pi-v channel ~ simply momentum direction of pi; in rho-v channel, linear combination of pi+/-, pi0, and neutrino momenta
- further investigation needed, sometime reconstructed polarimeter using neutrino momentum is far from MC
- Mid-point method for failed events in cone method: correct correlation with MC seen, but differences are still large
Q: P11, both tau plotted?
A: Yes
Q: mid-point method is not for surface?
A: not at this moment
Q: how are two neutrino momenta determined?
A: explained in P7
Q: should be better just using visible energy in single pi decay.
A: yes, but the polarimeter method can be extended to include ISR.
Q: how about a1 and leptonic decay?
A: a1 possible, leptonic not possible with this method due to too many neutrinos, need another method
C: need to study how the methods are affected by detector effects, e.g. allowed cone sizes should be smeared by detector resolutions
— Radiative Charged Seesaw Mechanism & Implications to ILC (K. Yagyu)
- so far no SUSY, no extra Higgs, no DM..
- exciting news muon g-2, deviation with SM is larger 4.2sigma
- 31 papers next day
- not established, LQCD results is consistent with experiments, to wait
- radiative charged seesaw
to explain Fermion mass hierarchy;
to explain mu (or e) g-2 anomaly
- Dark sector, Vector Like-fermions, Inert scalars, Dark matter, connect with SM via quantum effect -> e/mu lepton mass & g-2 anomaly
- to give muon mass, M_VLf ~ O(1) TeV; to give electron mass, M ~ O(1) PeV
- sign of correction to g-2 is fixed: +; magnitude ~ (m_l / M_l)^2
- presented allowed parameter regions
- consistency with DM relic density & direct searches
- implications to ILC:
Yukawa couplings do not obey simply proportionality with mass; deviation is suppressed by loop-factor, but can still be sizable, ~O(1)
Direct searches with e+e- -> new scalar pair -> DM pair + WW, reaction happens only for opposite e+e- chirality, unlike SM background e+e- ->WW which required same chirality
Measure muon- / electron- Yukawa couplings!
beam polarization is very helpful!
Q: kappa_l flavor independent?
A: no, M_l can be different
Q: for direct searches at ILC, SM WW requires helicity flip?
A & C: yes, e+e- same chirality but opposite helicity
Q: how large can the electron Yukawa coupling be?
A: up to ~100%
C: ongoing analysis by Y. Aoki e+e- -> gamma Higgs can probe electron-Yukawa coupling, but is still not sensitive to even 100% larger y_e
Q: is there special role for tau Yukawa coupling term in your model?
A: realized at tree-level, no particular role on g-2, simply because m_tau is large, no need to generate with quantum effect.
— Kinematic fitting for arbitrary resolution functions (Y. Kato)
- develop kinematic fitter based on log-likelihood method, to deal with non-Gaussian detector response
- algorithm implemented and tested in e+e- -> ZH -> mu mu bb @ 250
Sequential Quadratic Programming method
Hessian matrix approximated by damped-BFGS method
size of iteration step is adjusted by Armijo condition
b-jet energy resolution as a function of jet energy, polar angle; modeled by Crystal Ball function
preliminary results look reasonable
proof of principle completed
- going to study signal process of exotic Higgs decay e+e- -> ZH -> mu mu + 4-b @ 250 GeV and apply kinematic fitting
C: very interesting for searches, might be not ideal for kinematic fitting due to appearance of 4 b-jets, more degree of freedom.
C: from statistical point of view, Z->qq might be dominant
A: start from mu channel and see how it goes
— Discussions (all participants)
- next general physics meeting, July 14, Wednesday from 10:30am
- to invite Sumino san for talk on top mass at LHC & ILC
- monitor recent ILC papers by theorists, try to invite some of them for future meetings
- LHC-ILC synergy: EFT; discussed how to proceed; JT to contact Okamura san from ICEPP (for flavor tagging and machine learning discussions already started)
- long discussion on conveners change: invite Daniel Jeans to serve (agreed); Yonamine san, Kurata san, Ishikawa san stepped aside; confirm theorists to keep them or propose others; conveners need to be active and effective!