20100116-e

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13th General Meeting of the ILC Physics Subgroup Meeting
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January 16 (Sat) at Room 425, Building 3, KEK
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0) Attendants:
H.Ono (NDU)
T.Tanabe (ICEPP)
T.Suehara (CEPP)
Y.Takubo (Tohoku)
T.Saito (Tohoku)
H.Yamamoto (Tohoku)
Y.Okada (KEK)
J.Tian (Tsinghua)
Y.Kiyo (KEK)
K.Ikematsu (KEK)
F.Uchiyama (KEK)
K.Fujii (KEK)
R.Yonamine (Sokendai)

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Reports from Subgroups
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0) Opening Comments
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1) ZH subgroup
- qqH: Ono
- 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:
- Common event selection criteria with SiD
-> efficiency = 53% (cc), 56% (bb), 44% (Higgs BG), 5% (SM BG)
- Template fitting
Investigating binning effect:
-> Try smoothing
-> Br(cc)/Br(bb) = 0.058 +/- 0.014 : 23.4% (12.3% before smoothing)
Next Step:
- Check the number of events in each bin and apply smoothing only where applicable
- Reconsider the original cuts to improve measurement accuracies

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}
Polarization: use (Pol_e-,Pol_e+)= (+80%, -30%) to suppress WW BG.
Event selection
7.5 sigma signal --> delta sigma_ZH * Br(H->WW*) = 13.3%(relative)
Jet angle in W rest frame.
- Looked at phi between two decay planes by IDing charm quarks (eff_c=0.5 purity_c=0.8)
--> Reconstructed phi distribution roughly reproduced the generated one
--> Reconstructed phi distributuion has a dip at phi = 0.
--> jet clustring bias?
Next Step:
- Investigate mis-ID effect of c
- Z->ll + W->l nu + W->c down
- Prepare a generator with anomalous couplings and see how reconstructed distributions respond to the change in the couplings

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2) ZHH
ZHH -> qqHH : Takubo
ZHH -> llHH : Junping
2-1) 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:
Quick simulation
- Event Selection for llHH with MVA
--> S = 2.7, ZZZ BG = 0.48 --> significance 2.48 sigma
- ZHH -> qqbbWW* moe
WW* -->qqqq: 45%
Looked at ymax, Mh1, Mz, Mw1, Mh2
NN --> 1.0 signal 338 tt BG
- WW* -> lnuqq: 45 %
11.8 ZHH v.s. tt BG dominant : 4800
Full simulation
- Comparison with quick simulation results

Next Step:
- Convert more BG (3-4sec/event)
- Get used to Marlin framework
- Optimize lepton selection
- NN training for ZZZ BG

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4) New physics subgroup
4-1) AMSB (Reported by T.Tanabe)
AMSB : breaking of superconformal symmetry
- Phenomenology
- delta chi_1 = m_chi^+_1 - m_chi^0_1 ~ m_pi
- Generator
Chi^+_1 decay in Geant4
--> helicity angle distribution is strange.
- Reconstruction
a) 2 chargino tracks
b) 1 chargino track + 1 pion track
c) 2 pion tracks --> 2-photon BG?
--> endpoint analysis
Next Step:
- BG from full SM sample + 2-photon pipi, beam induced BG
- Endpoint fit
--> How well can we determine mass, mass difference, ...
--> What about threshold scan?
--> X-section as a function of Ecm.

4-2) Model Discrimination @ 500 GeV (I) (Reported by T.Suehara)
Status:
Dark Matter Particle:
SUSY: R --> neutralino : J=1/2
LH : T --> heavy photon : J=1
Inert Doublet Model : Z2 --> dark H : J=0
Observables:
Masses of DM and its parent X particle from E_W
Angular distribution of X produciton --> X spin
Simulation
Full simulation @ 500 GeV
--> selection efficiency ~ 20%
Next Step:
- Mass fit
- Production angle (W charge targ?)
- Threshold scan.
--> Paper to be submitted before Beijing.

4-3) Model Discrimination @ 1 TeV (II) (Reported by T.Saito)
Status:
- Look at production angle distributions for different cases
--> |cos th1| vs |cos th2|
--> Template fitting
--> Possible to discriminate different models.
- Threshold scan
alpha = 1.5 (DH), 0.58 (SUSY), 1.60 (LHT)
--> Need to take into account errors
Next Step:
- Investigate the error on the threshold scan.

4-4) 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.
--> Fixed the generator to take into accout the mass degeneracy of 3 flavors.
--> Only electron mode has large cross section.
--> Tau mode might be feasible.
- Event selection
*) e nu qq (1st KK: 100 GeV, 2nd KK: 300 GeV)
--> delta sigma/sigma = 5.6% (normal), 0.4% (inverted), 0.5% (degenerated) for 1st KK
--> delta sigma/sigma = 2.9% (inverted), 3.3% (degenerated) for 2nd KK
Next Step:
- Higher KK (3rd and 4th) modes @ 1TeV.
Q: Why mu and tau so small?
A: Because of the MNS matrix.

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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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*) Next target is Beijing LCWS.

Meeting Schedule:
Next general meeting (2010/03/13 10:30)
LCWS in Beijing : March 26-30 2010

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

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