20080906-e

*******************************************************
11th General Meeting of the ILC Physics Subgroup Meeting
*******************************************************

September 19 (Sat) at Room 425, Building 3, KEK
--------------------------------------------------------------------------------
0) Attendants:
H.Ono (NDU)
D.Harada (Sokendai)
T.Tanabe (ICEPP)
Y.Takubo (Tohoku)
T.Saito (Tohoku)
K.Yoshida (Tohoku)
M.Asano (Tohoku)
Y.Okada (KEK)
K.Ikematsu (KEK)
I.Fleck (Siegen)
Y.Kiyo (KEK)
H.Itoh (ICRR)
K.Fujii (KEK)

Via TV:
J.Tian (Tsinguha)
N.Maeda (Hiroshima)
H.Yamamoto (Tohoku)

------------------------------------
Reports from Subgroups
------------------------------------

0) Opening Comments
Q: Physics panel activities?
------------------------------------
1) ZH subgroup
- nunuH : completed by Yoshida in LOI
- qqH : Wenbiao in LIO + this analysis
- llH : being looked at by Yoshida

1-1) qqH analysis (Reported by H.Ono)
Status:
- There is large discrepancy between Wenbiao's and SiD's.
Now using standard ILD sample with the standard SM BG.
- Analysis procedure
* forced 4-jet clustering with Durham jet finder.
* chi2 to select best combination
* BG reduction cuts w/o flavor tagging
* template fitting
Next Step:
- Understand the difference from Wenbiao's
- NN
- Publication
Q: Are the emplates include mis-combinations?
A: Yes.
Q: What is the fraction of mis-paring of jets?
A: Will investigate.

1-2) ZH -> llH analysis (Reported by K.Yoshida)
Mh=120GeV
Ecm=250GeV, Pol=(-80,+30), 250 fb^{-1}
ZH -> eeH : 11.1 fb
ZH -> mumuH : 10.4 fb
Status:
eeH:
- Event Selection
~60% signal efficiency
<O(1%) BG efficiency
- Results
delta Br(H->cc) = 28.9%
delta Br(H->bb) = 2.63%
mumuH:
- Event Selection
~60% signal efficiency
<O(2%) BG efficiency
- Results
delta Br(H->cc) = 29.5%
delta Br(H->bb) = 2.63%

Next Step:
- Check PFO ID and Lepton ID.
- Make rBG free in the template fitting.
Q: eecc / mumucc seems to be inconsistent with eeH/mumuH. Why?
A: Will check on it.

------------------------------------
2) ZHH
ZHH -> qqHH : Takubo
ZHH -> llHH : Junping
2-1) ZHH -> qqHH full simulation (Reported by Y.Takubo)
Mh=120GeV
Ecm=500GeV
0.5 ab^-1
Pol:(e-,e+)= (-80,+30)
HHqq : 157 ab
BG total: 414 fb
Status:
- Event selection
Nb=3, Nb>=4
Likelihood analysis:
chi2(ZHH), chi2(tt), Mh, MZ, Mw, Etop, Emiss, Thrust angle,
c-likeness for Z, total b-likeness, c-likeness, Nb, Nc
Remaining BG
Nb>=4 --> qqbbH --> signal 6.6 BG: 38.3
Nb=3 -> 6f --> signal 8.8 BG: 512.6
--> 1.1 @ 0.5 ab^{-1} which means 3.1 @ 4 ab^{-1}
--> Needs better flavor-tagging
- NN training for LCFIVertex @ 140 GeV

Next Step:
- Further investigate the impact of the new NN training.
Q: Is signal diagaram excluded from the 6f BG sample?
A: Will check on it.
C: Use Tanabe-san's tbtb BG generator.

2-2) ZHH -> ll(bb)(bb) and qq(bb)(WW*)(Reported by J.Tian)
sigma=152ab @ Ecm=500 GeV w/o beam polarization.
Mh = 120GeV
quick simulation.
2ab^{-1}
Status:
- Event Selection for llHH with MVA
--> S = 2.7, ZZZ BG = 0.48
- ZHH -> qqbbWW* moe
WW* -->qqqq: 45%
Looked at ymax, Mh1, Mz, Mw1, Mh2
--> Signal = 1.1, BG (tt) = 2644
--> impossible! (previous results)
- WW* -> lnuqq: 45 % (not yet)
under investigation.
Next Step:
- more BG, ZZZ, tbtb
- optimization of cuts and NN
- WW* -> lnuqq
- full simulation

------------------------------------
3) TT Threshold Enhancement (Reported by Y.Kiyo)
- Preturbative region: >50 GeV above threshold
tree vs 1-loop : 10% enhancement
1-loop vs 2-loop : quite small
--> 1-loop is enough --> alfs/pi
- Near threshold
NR approx.
--> Accidentally NR approx and tree+1-loop
--> Found a new overlooked width related factor.
--> Matching point arount E=20GeV.

------------------------------------
3) TTH (Reported by K.Ikematsu)
Ecm=500 GeV with 1ab^{-1}
Status:
- NRQCD Correction to X sections
sigma_ttH = 0.45 fb with no beam polarization.
sigma_ttZ x Br(Z->bb) = 0.2 fb
sigma_ttg(g->bb) = 0.7fb
- Event Selection (L+6 jets)
S=23 B=32 --> 4.1 sigma --> delta g_Y /g_Y = 0.12 for pol=(0,0)
S=38.9 B=52.8 --> 5.4 sigma --> delta_Y/g_Y = 0.093 for pol=(-80,+30)
C: top Yukawa effect at tt threshold quickly vanishes as Mh goes up from Mh=110GeV to 120GeV.
Next Step:
- Include 8-jet mode.
- MVA
- accuracy as a function of Ecm
- Full simulation + high performance flavor tagging.

------------------------------------
4) AA->HH (Reported by N.Maeda)
Status:
- Sensitivity study
--> E_AA=260-270 GeV is optimum.
BG (WW: 90 pb), while S ~ 0.04 fb
--> E_AA below tt BG
--> signal cross section x luminosity -> 16 events / year (10^7 sec)
(sigma_eff(S) = 0.013 fb, (sigma_eff(BG) ~ 12pb)
- Event Selection (HH -> 4b)
Preselection with b-tag (n-sig) requring 2 loose + 1 tight b-jets.
NN (JetNet)
chi2 (H, W), #tracks, Pt, Pl, Evis, ycut, Nb
--> 5 years
Signal = 16x5xeff = 12.5
BG = 1.5 x 10^7 x 5 = 3.9
--> 3.1-sigma (2.7-sigma for cut-based analysis)
--> Other BG: ZZ becomes the next problem.
6fb/0.013fb = 500 --> BG x10 larger even after perfect 4b-tag
Next Step:
- AA -> ZZ BG
- HH -> bb WW* (BR=0.18)
- To study remaining BG events with MC truth
- Other BG (AA -> 4b)

------------------------------------
5) H->WW* (Reported by K.Fujii on behalf of N.Okada)
- New topics to be studied by
R. Neil Hodgkinson, N. Okada, Y.Takubo, K.Fujii, ...
- Anomaly in HWW couplings.
- SM type, H(EE-BB) type, HEB type

------------------------------------
5) New physics subgroup
5-1) Right-handed Neutrino (Reported by T.Saito)
Status:
- Setup
NuR in the bulk
--> M_NuR = O(100GeV) and y = 0.1 possible.
- Created event generator --> physsim
--> t-channel diagram dominates.
- Event selection
mu nu qq to avoid SM enuW BG.
--> energetic isolated muon, M2j ~ mW
- Look at M(l-W)
Next Step:
- Different parameters.
- Higher KK modes.

------------------------------------
6) tt g(g->bb) (Reported by T.Tanabe)
Status:
A ttg(g->bb) generator has been completed and included in physsim
- Necessary for may important processes including ZHH, ttH, ...
- To use full helicity amplitudes including W decays.
- Probelms:
Color connection.
--> Compare (tbar)(tbarb) with (ttbar)(bbar) and take the difference
as a systematic error.
Cross section
-> 763 ab (physsim) 679 ab (MadGraph)
Next Step:
- Check the systematic error.

---------------------------------------------------------
The slides shown at the meeting is available from
http://ilcphys.kek.jp/meeting/physics/
see them for details.
---------------------------------------------------------

------------------------------------
Discussions on future direction and mile stones
------------------------------------

Meeting Schedule:
Next general meeting (2009/11/21 9:30) -> Link with Detector Meeting ?
Annual meeting on Dec. 2-3.
LCWS in Beijing : March 2010

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

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