20080906-e

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9th General Meeting of the ILC Physics Subgroup Meeting
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Apr. 11 (Wed) at 1F Big Meeting Room, Building 2, KEK
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0) Attendants:
N.Okada (KEK)
Y.Okada (KEK)
H.Ono (NDU)
D.Harada (Sokendai)
R.Yonamine (Sokendai)
K.Ikematsu (KEK)
T.Suehara (ICEPP)
S.Kanemura (Toyama)
Y.Takubo (Tohoku)
E.Asakawa (Meiji Gakuin)
K.Fujii (KEK)

Via Video Conference System:
M.Asano (Tohoku)
N.Maeda (Hiroshima)

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Reports from Subgroups
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1) ZH subgroup
1-1) ZH (Reported by H.Ono)
Status:
- Ph.D thesis finished. --> congratulations!
ZH -> nu nu qq
- GLDPFA : sigma_Ej/Ej < 30%/sqrt(Ej) for Ej=45 GeV
- PandraPFA reaches almost the same level of performance as the Cheated PFA
ZH -> 4 jets
Q:
Next Step:
- shift to new full simulation tools for ILD
- new topics

2) ZHH (Reported by Y.Takubo)
Mh=120GeV
HHnunu : 40 ab
HHqq : 135 ab
1-1) HHqq
Status:
- Event selection
chi2 cut
Mass cut (Mh & Mz)
Missing Pt
6-b requirement
- Status of S/B
3.8(ZHH) + 0(tt) +0.5(tbtb) -> observation seems possible
ttg & tth contributes to the remaining tbtb BG.
Q: How are t and tbar decayed?
A: By the decay package of MadGraph
- NN analysis
--> Try the same variables as used in the simple cut method
Next Step:
- More realistic b-tag with full simulation
- NN analysis
- HHnunu will be added, no data available for the moment.
*) Tsinghua group started looking at WW* mode.
Q: How to generate ttbb?
A: tt(g->bb) -> ttbb -> parton shower.

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3) TTH (Reported by R.Yonamine)
Status:
- Currently working on the l+6j mode
Threshold enhancement ~ a factor of 2 at Ecm=500 GeV for Mh=120 GeV and Mt=175 GeV.
- S/B ~ 4.4 for 1 ab^{-1} with tt(g->bb) not included
Next Step:
- ttg->ttbb BG (~ 0.7fb) --> probably OK if Mbb ~ 120 GeV is required.
- Utilize beam polarization
- 8-jet mode
- H->WW*
- Full simulation

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4) AA->HH
4-1) Theory (Reported by D.Harada)
Status:
New phys effects may appear as anomaly in the self-coupling (delta kappa)
- dim-6 effect
- non-decoupling effect
top loop ~ -10% (prop. to mt^4)
- AAHH @ PLC
Features:
2-body -> kinematical advantage
Loop induced
Helicity selection
--> Anomaly in self-coupling appears near the threshold
--> We can tune Eee for mh
In the case of THD model
-> M^4 term appears in 1-loop correction
-> Cross section enhancement near the threshold
-> enhancement prop. to M^4
-> 3 peaks: threshold (h), tt, H+H-
gg->HH
160<Mh<180 GeV --> 30% measurement
--> becomes very difficult otherwise even at SLHC.
--> very asymmetric errors due to interference between box
Nest step:
- Discuss what to do with gg->HH
- WW -> hh @ LHC

4-2) Exp (Reported by N.Maeda)
Status:
- Sensitivity study
1st assume 100% efficiency for S and no BG
--> E_AA~300 GeV is optimum.
2nd with BG (WW: 90 pb), while S ~ 0.04 fb
--> 10^{-6} suppression for BG is necessary even with 100% efficiency for S
to achieve sensitivity ~ 3.
--> signal cross section x luminosity -> 16 events / year (10^7 sec)
(sigma_eff(S) = 0.013 fb, (sigma_eff(BG) ~ 12pb)
- Simulation tools
HELAS/BASES/SPRING with Luminosity spectrum
- Analysis results
Compare chi2 for hh and chi2 for WW and choose the hh region
--> S/B not enough.
b-tag
If we assume el=0.005, ec=0.10, and eb=0.7
-> eta(B) = 3x10^{-8}
eta(S) = 0.1
-> n-sig method: eta(B) = 1.5x10^{-6}, eta(S) = 0.16
-> combined with chi2 cut and Ech > 2 GeV
0 BG event remained for 10^{7} events
21 signal events for 10 years (eta(S)=0.132) -> 4.6-sigma
--> It seems possible to observe the signal in 10 years.
Next Step:
- Other BG
C: Comment on the positron line in the PLC figure -> should be electron beams
C: Specify Ee.
A: Ee ~ 180 GeV -> no tt BG
C: bb(g->bb) BG

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5) New physics subgroup
5-1) Theory (Reported by M.Asano)
*) Generic WIMP studies
X+/- -> W+/- X0
Possibilities:
X+/- X0 (DM)
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0 0 : Dark Higgs
0 1 : unknown
1/2 1/2 : SUSY
1 0 : unknown
1 1 : LHT
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How can we distinguish them experimentally?
- Mass determination -> mass relation
- Total cross section
- Angular distributions
--> production angle distribution tells the spin
--> W polarization tells the decay vertex structure.
--> If t-channel particle is heavy, there will be no asymmetry.
--> Big asymmetry if t-channel contirubtion is significant.
--> Jet charge ID
Plan:
@500 GeV ILC : full simulation --> M_DM=43.7 GeV, M+/- = 23 GeV
@ 1TeV ILC: qucik simulation -->M_DM = 81.9 GeV M+/- = 368 GeV
C: There exists heavy lepton sector mixing <-- LFV constraints
--> futher LHT studies (heavy lepton production)

5-2) Theory (Reported by N.Okada)
New particles (mass, spin, ...)
New interactions (completely new, anomalous SM, ..)
*) Precision measurements of anomalous couplings
e+e- -> tau+tau-, ttbar
Exp: full simulation -> level of precision
Th: new physics effects on differential cross section,
initial/final state polarization, top width
--> flavor dependent Z' model (extra U(1))
Y = Y1 + Y2
LHC can find Z' -> l+ l- if MZ' ~ 1.5TeV
*) Distinguish WIMP DMs
--> DM and associated new charged particles
*) Type II & Type III seesaw in ILC
*) Hidden X production
--> Z gamma fusion --> T/L separation
Next Step:
- simulations

5-3) Exp-1: Tau/SUSY (Reported by T.Suehara)
Full simulation studies with ILD framework
Status:
Tau:
- Cross section and A_pol
-> Sensitive to MZ' up to 5TeV
SUSY:
Chargino/neutralino separation (chargino -> W+LSP, neutralino -> Z+LSP)
- gamma gamma -> WW BG turns out to be important
-> will investigate it with higher statistics
Cross section (arbitrary unit)
52.8+/-1.1 (2%)
7.6 +/-0.5 (6%)
- mass fit --> delta M <~ 1 (0.6) GeV for X+/- (X0) with 500 fb^{-1}
- production angle
- W/Z decay helicity angle
Jet clustering:
Modified ZVTOP (1event/1min)
--> Slow but very good performance
Next:
- tau tau (+ tt) -> Z' studies
- SUSY -> generic DM studies.

5-4) Exp-2: Top (Reported by K.Ikematsu)
Full simulation studies with ILD framework
Status:
Kinematical Fit (7C: 4C(4-momentum) +2C(mW) + 1C (mt1 = mt2)
-> mt line shape now as good as those from other studies
-> Lineshape function should be improved for mass fit.
delta sigma_tt / sigma_tt = 0.40 % @ 500 fb^{-1}
delta Mt =90 MeV, Gamma_t = 60 MeV @ 100 fb^{-1}
Next Step:
- New physics subgruop: l+4-jet
-> Angular analysis
- A_FB (vertex charge)
--> Z' studies together with tau tau

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6) LHT
6-1) Exp (Reported by Y.Takubo based on R.Sasaki's JPS talk)
A paper has been accepted for publication in PRD and its proof
has just been sent back to the publisher.
The results has also been integrated into the ILD LoI.
Simulation Conditions:
- Z_H -> A_H + h (100%) @ 500 GeV
AH=82GeV, ZH=369GeV, h=134 GeV
sigma_S=1.9fb
H decay : BR(bb)=55%, BR(WW*)=26%, BR(cc)=6.3%
- W_H W_H
m(WH) = 368 GeV, m(AH) =82 GeV
sigma_S=277 fb @ Ecm=1TeV with 500 fb^-1
W_H -> A_H + W (BR=100%)
Status:
*) Z_H A_H
- event selection
Mh cut, cos(th), Pt cuts
--> S/sqrt{B} = 3.7
- Edge fit -> masses
--> M_AH = 83 +/- 13 GeV, M_ZH = 366 +/- 16 GeV @ 500 fb^-1
*) W_H W_H
- High statistics very clean sample available
- Edge fit -> masses
--> M_AH = 81.58+/-0.67 GeV, M_WH=368.3+/-0.63 GeV
- delta f = 580+/-0.69 GeV
- delta kappa = 0.8%
Nest Step:
- ISR+beamstrahlung
- full simulation @ 500 GeV

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7) Comparison of ILD and SiD L'sOI (Reported by Y.Takubo)
7-1) ZH Recoil mass
7-2) H decay branchinf fractions
7-3) Tau
7-4) Top
7-5) SUSY

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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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TILC09:
ZHH: Exp by Y.Takubo
ZH: Exp by H.Ono -> phys+benchmarking
AAHH: Exp by N.Maeda (No theory talk) --> joint session with gamma-gamma : 14:00~15:30, Apir 19
TTH: Exp by R.Yonamine
LHT: Th+Exp by Y.Takubo
TT: Exp by K.Ikematsu -> phys+benchmarking
SUSY+tau tau: Exp by T.Suehara -> phys+benchmarking
Generic DM studies: Th (+Exp) by M.Asano
Physics Session Summary Speaker: N.Okada
Benchmarking Summary: to be covered by T.Suehara if possible

Next bi-weekly meeting (2009/04/30 13:00)
Next general meeting (2009/06/13 9:30) -> Link with Detector Meeting

"Proceedings of the ILC Physics WG Meetings", KEK, May, 2007 ~ May, 2009
Proceeding deadline: the end of April 2009:
Anybody can contribute even if he or she was not present at the meeting.
Contributors are encouraged to include most updated results at the time of submission
of their proceedings papers.

StdHEP output for DH and LHT events --> Fujii
Generator development of ttbb and its StdHEP output --> Fujii
Bootcamp for experimentalists in May?
--> generator generator's tutorial

Working group contact persons:
K.Ikematsu, Y.Okada, H,Ono, S.Kanemura, Y.Takubo, K.Fujii, T.Suehara

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

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