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15th General Meeting of the ILC Physics Subgroup Meeting
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May 15 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
Y.Takubo (Tohoku)
H.Ono (NDU)
Y.Kikuta (Sokendai/KEK)
Y.Yamamoto (Sokendai/KEK)
T.Takahashi (Hiroshima)
T.Saito (Tohoku)
Posch (Sokendai/KEK)
S.Kawada (Hiroshima)
J.Tian (Tsinghua)
M.Asano (Tohoku)
E.Kato (Tohoku)
Y.Kiyo (KEK)
T.Suehara (Tokyo)
T.Tanabe (ICEPP)
H.Itoh (KEK/ICRR)
Y.Okada (KEK)
D.Harada (KEK)
Y.Okada (KEK)
K.Fujii (KEK)
Via video
K.Ikematsu (Siegen)
H.Yamamoto (Tohoku)
Kamai (Tohoku)
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Opening Comments
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Reports from Subgroups
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[A] Symmetry breaking & mass generation
1) ZH subgroup
1-1) xxH analysis (Reported by H.Ono)
Status:
- Setup: mh=120GeV, 250fb^-1@250GeV, Pol(e+,e-)=(+30%,-80%)
- qqH:
efficiency = 53% (cc), 56% (bb), 44% (Higgs BG), 5% (SM BG)
- nunuH:
efficiency = 45% (cc), 45% (bb), 35% (nunuH), 0.04% (SM BG)
- C.L. Template fitting
Introduced C.L. templates to reduce the binning dependence.
Next Step:
- Binning dependence has been improved significantly but there is
still some problem remaining -> to be investigated.
- Publication as soon as this binning dependence problem will have been solved
- New benchmark processes.
Q: What is your prospect for H -> glue glue
A: We will try the C.L. template method, but the template shapes for H -> WW* and gg
are similar.
C: H -> WW* can be positively identified.
1-2) ZH -> nunuH followed by H->WW* (Reported by Y.Takubo)
N.Hodgkinson, N.Okada, K.Ikematsu, and K.Fujii
Status:
- Looking for anomaly in the HWW vertex:
a/Lambda : HWW
b/Lambda : HW_{\mu\nu}W^{\mu\nu}
b~/Lambda : HW_{\mu\nu}~W^{\mu\nu}
- MC conditions
mh=120GeV, 250fb^-1@Ecm=250GeV -> Br(H->WW*)=15%
Polarization: use (Pol_e-,Pol_e+)= (+80%, -30%) to suppress WW BG.
- Event selection
mh, mm, cos_h, y-value, Etk<30GeV, Nb<=1 -> likelihood cut
-> 7.4 sigma signal --> delta sigma_ZH * Br(H->WW*) = 15%
Jet angle in W rest frame.
- Looked at phi between two decay planes by IDing charm quarks (eff_c=0.8 purity_c=0.2)
--> Reconstructed phi distribution by fitting mh distributions for different phi bins.
--> Asymmetry seen as expected.
- Prepared a physsim generator with anomalous couplings and generated MC events with anomalous
coupling.
- Looked at the phi distributions for the generated events and investigated if the deviation
from the SM case is detectable.
Next Step:
- Draw a contour plot to show the sensitivity to a, b, and btilde.
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2) ZHH
2-1) ZHH (Z->ll) full simulation status (Reported by Junping)
Status:
- Event selection for full simulation MC sample
lepton ID: E_cone(charged) turned out to be a better quantity than E_cone(all)
-> Optimized the cone angle and the cut in the (E_l, E_cone) plane.
-> Efficiency ~ 98% for leptons
< O(2%) for hadrons
- M_ll distribution: similar for both electrons and muons
Next Step:
- About 10% efficiency improvement with about 1% purity drop.
- ll4b, nunu4b, qq4b, and qqWW*
- New BG: ZZH (WWH will not be a problem but ZZH could be).
- WW fusion at 1TeV.
3) Top Yukawa in TT
3-1) Theory (Reported by Y.Kiyo)
Status:
- Can we measure the effect of H exchange?
SM: 9(4) % for mh=120(200)GeV
1-loop: +6(3)%
h+QCD: +3(1)%
SUSY: (~2HDM) 5% effect (-5% compared to the SM case,
which is due to the highs mixing angles, alpha and beta)
--> 4% or better theoretical accuracy desired to see the effect
- Big scale variation even after including 3-loop (NNLO'/NNLL') corrections
QCD: NLO, NNNLO'/NLL'
EW:
Why?
- RG improvement to the static QCD potential stabilizes the variation significantly
--> Though we need to improve NNNLO'/NNLL', we can hope that top Yukawa can be measurable.
Next Step:
- Improve NNNLO'/NNLL'.
C: Check the top Yukawa effect for H->gg.
Q: Time scale?
A: ~ 1 month.
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3) TTH
3-1) TTH (Reported by T.Tanabe)
Status:
- We have looked at the validity of the signal MC, the QCD correction, in particular.
--> The correct function from a theorist, Yokoya-san, has been compared with the
currently used heuristic one. The difference turned out to be small.
Nest Step:
- We are going to weight the results.
- Then publish the results.
4) AA->HH Group
4-1) Experiment (Reported by Kawada)
Status:
- Updated the previous results by increasing statistics of ZZ BG to 1M events
- NN analysis
1st step: HH vs WW
2nd step: HH vs ZZ+WW (after filter 1)
--> significance 1.16 sigma
- Kawada (M1) took over Maeda's work.
Next step:
- Other BG like AA->bbbb.
- Verify the current scheme of AA->ZZ generation assuming on-shell Z's in the helicity eigen-states.
C: The current scheme is probably OK.
C: We will look into the program together with Posch-san.
- Investigation of statistical independence of training and analysis samples.
Q: Should we try a Higgs mass other than Mh=120GeV?
C: It is meaningful to try Mh=130, 140 GeV.
C: We had better publish our result now, since if we change Mh, we will need to generate new WW BG
sample at the new optimized energy.
4-2) Theory
Status and Plan:
- Writing a paper.
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[B] New physics
1) Right-handed Neutrino (Reported by T.Saito)
Seasaw: Mnu = v^2 y^2 / 2 M_N
--> XD can make y small
--> M_N = (2n-1)/2R in TeV scale XD model --> can be as light as O(100GeV)
Status:
- Setup
Seasaw: Mnu = v^2 y^2 / 2 M_N
--> XD can make y small
--> M_N = (2n-1)/2R in TeV scale XD model
--> M_N = O(100GeV) and y = 0.1 possible
--> M_N = 150GeV to avoid the LEP constraint.
- M_NR measurements
*) e nu qq (1st KK: 150 GeV, 2nd KK: 450 GeV, 3rd KK: 750 GeV)
Degenerate case:
500fb^-1@500GeV
1st KK: 0.42%
500fb^-1@1TeV
1st KK: 0.7%, 2nd KK: 3.0%, 3rd KK: 12.0%
Inverted case has similar precisions
In the normal case, only 1st KK can be observed.
*) tau nu qq
forced 3-jet clustering, tau jet ID, W reconstruction,
then likelihood analysis -> significance 4.0
-> No peak -> Difficult to observed the tau mode.
Next Step:
C: Use the measured M_NR in the electron mode analysis and estimate the tau
energy as E_tau = E_NR - E_W, then we can calculate M_NR much more accurately.
Q: Is the LFV constraint imposed?
A: Yes. That's why we hat to use electrons instead of muons.
2) LHT: ZHZH (Reported by E.Kato)
Status:
- MC Conditions
Same as the previous LHT publication
- Study the effect of the energy resolution
- Study the shifting of the energy edges.
--> The shift is significant: delta E = 26 GeV (all), 15.1GeV(bb), 33.6GeV(WW)
estimated by e+e- -> ZH @ Ecm=250GeV
--> average shift turned out to be delta E = 21.8GeV
C: Leptonic W decays should be removed for the mass measurement.
--> Problem: 2 peaks in M_ZH distribution.
Next Step:
- Understand the 2 peaks.
- Update the event selection criteria.
3) Model Discrimination
3-1) @ 500 GeV (I) (Reported by T.Suehara)
3 generic cases to be discriminated:
a) J=0: Inert H-like model
b) J=1/2: SUSY-like case
c) J=1: LHT-like case
- Event selection study using full simulation (signal and BG) samples
--> Performance good enough for the E_W end-point study.
- Mass determination
delta E_W = O(0.1(0.5)GeV) for 200(40)fb^-1
delta M_X = O(0.1(0.5)GeV) for 200(40)fb^-1
delta M_DM = O(0.5(2)GeV) for 200(40)fb^-1
- Angular distribution
200fb^-1 -> Separation possible
40fb^-1 -> Some separation
Next Step:
- 25 mass points (5 M_X and 5_DM) to investigate the effect of mass errors.
--> Use Reco/MC ratio? -> several days
- Threshold scan (Toy MC?) -> 1 day
- Write a paper -> 1 dedicated week?
3-2) @ 1 TeV (II) (Reported by T.Saito)
Status:
- E_W endpoints
-> delta M_DM ~ 1% if X-section = 200 fb with 500fb^-1.
- Production angle distributions
--> |cos th1| vs |cos th2|
--> Template fitting
--> Possible to discriminate different models.
--> Effect of the mass error.
- Threshold scan
Fit region; 740~800 GeV assuming the same X-section @ 1 TeV
--> model discrimination seems possible with 200 fb.
Next Step:
- Analysis completed.
- Prepare for the publication.
Q: Why 40fb and 200fb?
A: IH: 3fb, SUSY: 110fb, LHT: 300fb
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The slides shown at the meeting is available from
http://ilcphys.kek.jp/meeting/physics/
see them for details.
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Discussions on future direction and mile stones
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*) Physics-Accelerator joint meeting
August 9-12 at Kama-saki onsen
*) Oct.18-22: ECFA/CLIC Meeting
Meeting Schedule:
Next general meeting (2010/07/17 10:00)
Working group web page:
http://www-jlc.kek.jp/subg/physics/ilcphys/
Slides are available from http://ilcphys.kek.jp/meeting/physics/