20080906-e

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16th General Meeting of the ILC Physics Subgroup Meeting
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July 17 (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.Saito (Tohoku)
Posch (Sokendai/KEK)
S.Kawada (Hiroshima)
E.Kato (Tohoku)
T.Suehara (Tokyo)
T.Tanabe (ICEPP)
Y.Okada (KEK)
D.Harada (KEK)
R.Settles (MPI)
R.Yonamine (Sokendai)
F.Borzumati (Tohoku)
F.Uchiyama (Tsukuba)
K.Fujii (KEK)

Via video
J.Tian (Tsinghua)

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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 = 40% (cc), 37% (bb), 32% (Higgs BG), 7% (SM BG)
- nunuH:
efficiency = 45% (cc), 45% (bb), 35% (nunuH), 0.04% (SM BG)
Next Step:
- 350 GeV analysis
- Binning dependence has been improved but there is still some problem remaining
such as difference between qqH and nunuH -> to be investigated.
- Publication as soon as this binning dependence problem will have been solved
- New benchmark processes.
H -> glue glue, WW*

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}
- Look at 3 variables
- phi, the angle between 2 decay planes in the H rest frame -> b, btilde
- p_W in the H rest frame -> a, b
- cos(theta_f) in the W rest frame. -> b, btilde

- 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
-> 7.6 sigma signal --> delta Br(H->WW*) = 15.7%
- (a,b), (a,tilde), (b,btilde) contours made for the SM MC sample
--> some problem in the definition of chi2 --> to be fixed.

Next Step:
- Fix the problem with the contours
- Check physics models
- Publish the results asap

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2) AA->HH Group
2-1) Experiment (Reported by Kawada)
Status:
- Issues
Other BGs
ZZ BG
4b BG
NN training
- Verified the scheme of AA->ZZ generation assuming on-shell Z's in the helicity eigen-states.
- Checked the NN training
--> consistent among Kawada's samples but some discrepancy with Maeda's sample.
Next step:
- 4b BG -> Kurihara san
- Compare distributions between Kawada's and Maeda's
- Write a paper.

2-2) Theory (Report by Harada)

Status:
THDM, Scalar LQ, & 4th generation
- top loop -> -10% in SM (non-decoupling)
- with new physics, X-section enhanced by
- new particle loop
- effective 1-loop huh vertex enhanced by non-decoupling effects
--> effect is small in the vector-like 4th generation
because of T-parameter constraint
Next step:
- Preparing a paper: to be published in 4 months.

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3) ZHH (Reported by Junping)
Status:
- Sensitivity
ZHH@500GeV: (delta lambda/lambda) = 1.8 x (delta sigma/sigma)
nunuHH@1TeV: (delta lambda/lambda) = 0.85 x (delta sigma/sigma)
- Analysis
- ZHH -> (ll)(bb)(bb) -> 2l + 4jets @ 500GeV (full sim.): completed
- nunuHH -> (nun)(bb)(bb) -> missing + 4jets @ 1TeV (fast sim.): completed
- ZHH -> (nun)(bb)(bb) -> missing + 4 jets @ 500GeV (full sim.): on going
- ZHH -> (ll)(bb)(bb)
signal: 4.93, BG: 0.50 -> ZHH excess: 3.6sigma significance for 2ab^-1
--> 5.4+3.5-2.3 events (68% CL interval) -> delta sigma/sigma = 54%
--> delta lambda/lambda = 94%
--> significance is expected to become 3.2 sigma if llbbH BG
- nunuHH -> (nunu)(bb)(bb) @ 1TeV (fast sim.)
--> signal significance: 2.5 sigma
--> delta lambda /lambda = 45%
Next Step:
- Finish ZHH -> (nunu)(bb)(bb)
- More BG for (ll)(bb)(bb)
C: Combine Takubo's (qq)(bb)(bb) result which has 2-sigma significance.

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4) TTH
4-1) TTH (Reported by T.Tanabe)
Status:
- Signal(tth): 0.45fb w/NRQCD correction (no beam pol.)
- BG: ttg(g->bb), ttZ(Z->bb), tt(reducible but large)
- NRQCD correction to ttH, ttZ
- Analysis
l+6jet: finished -> see prev. slides by Katsumasa or Ryo
8jet:
isolated lepton veto
y(9->8)cut, thrust, btag, mass
--> tth:14.7, tt:24.3, ttZ:11, ttg:5.9
--> 1.9-sigma with 1ab^-1
- Sensitivity to the Yukawa coupling (delta gt/gt)
--> no pol: 13.8% (3.6sigma)
(-0.8,+0.3): 10% (5sigma)
Nest Step:
- Publish the results.
- Move on to full simulation
C: y(8->7) should be used.

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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 allows large y and small M_N
--> 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.
- Today's topic: tau nu qq analysis
signal(normal): 5.49 fb
(inverted): 4.18 fb
- selection and reconstruction
Etau, MW, likelihood-enW, likelihood-emode, 80<MN<160
MN calculation with EN estimated from MN measured in the e-mode
--> signal significance: 6.2 (normal), 4.9 (inverted)
--> delta (sigma(tau)/sigma(e)) = 13.1% (normal), 12.4% (inverted)
Next Step:

- Submit the paper.

2) LHT: ZHZH (Reported by E.Kato)
- MC Conditions
Same as the previous LHT publication

- e+e- -> ZHZH followed by ZH->AH+H (mH=134GeV)
Status:
- Event selection

--> Improved with H->WW* rejection
--> left edge of E2j distribution becomes sharper
- AH-ZH 2D Mass fitting
--> 2 solutions: AH mass: 4.2% ZH mass: 1.3%
--> the false solution eliminated by performing simultaneous fit
with WHWH
mass --> AH: 1.3%, WH: 0.20%, ZH: 0.56%
Next Step:

- vev from combined fit of WHWH and ZHZH
- Move onto eHeH

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
-> clear model separation possible with 200fb^-1
--> studying the effect of mass measurement
- Threshold scan
--> 3-point fit to sigma(rs,n) = a(rs-rs0)^n with n=1/2, 3/2
@ rs=470, 500, 530 GeV with 50fb^-1 each assuming sigma=40fb
Next Step:
- Finish the mass shift study
- Write a paper
C: Fix the definition of the separation power.

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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
*) AD&I meeting on July 23.
*) BAW meeting on Sep.7 - 10.
*) Oct.18-22: ECFA/CLIC Meeting

Meeting Schedule:
Next general meeting (2010/10/09 10:30)

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

Slides are available from http://ilcphys.kek.jp/meeting/physics/