Taikan Suehara et al., ILC physics meeting, 2009/04/11 page 1

SUSY point5/Tau-pairSUSY point5/Tau-pairfull simulation studyfull simulation study

Taikan SueharaICEPP, The Univ. of Tokyo

Taikan Suehara et al., ILC physics meeting, 2009/04/11 page 2

• Tau-pairhttp://www.ilcild.org/documents/ild-loi-material/tau090316.pdf/at_download/file

• SUSY point5http://www.ilcild.org/documents/ild-loi-material/point5_090319_2.pdf/at_download/file

To be published??

Analysis notesAnalysis notes

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Tau-pair analysisTau-pair analysis

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[Observables] P(e-)=80%, P(e+)=30%, 500 fb-1

• σ, AFB (bg suppression)

• Polarization P()↑ Decay angle determination

Tau-pair processTau-pair process

σ=2600 fb-1 (e-Le+

R) σ=2000 fb-1 (e-

Re+L)

radiative events: ~70%

Difficulty on decay analysis

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BG suppressionBG suppressionBG suppression cuts

• # Track <=6• 1(+)+1(-) clusters• Opening angle >178 deg• |cos| < 0.9

• < 2 electrons, < 2 muons• 40 < Evis < 450 GeV• 30 < MaxE() < 240 GeV

Purity ~ 90% (almost bg free)

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Cut plotsCut plots

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σ: 0.33% (e-Le+

R), 0.37% (e-Re+

L) stat. error (count based)

AFB: 51.64 ± 0.29% (e-Le+

R), 44.18 ± 0.37% (e-Re+

L)

σ, Aσ, AFBFB

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• Leptonic (35.3% in total)– 「 Lepton ID 」 (high eff.)– P=0.22 (lost power by 2 s)

• Pinu decay (10.8%)– 「 only one 」 (simplest)– P=0.58 (full)

• Rhonu decay (23.7%)– 「 one +2 」　 P=0.49 (almost full)

• A1nu decay (12.9%)– 「 one +4γ 」 or 「 three 」 (each 50%)– P=0.45, 3-prong is useful.

Decay modes in ADecay modes in Apolpol analysis analysis

Branching ratio of tau

e17.9%

mu17.4%

pi10.8%

rho23.7%

a112.9%

misc17.3%

5 major decay modes

Minimize stat. error by

combining decay modes

P = analyzing powerM.Davier et al., PLB306 411 (1993)

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• Lepton ID• # Particle(charged neutral)• Invariant massDecay mode separation by

various information

a1 and a1 and 00 reconstruction reconstruction

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Mode selection (1)Mode selection (1)Leptonic mode

Pinu mode

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Mode selection (2)Mode selection (2)Rhonu mode

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Mode selection (3)Mode selection (3)A1 mode (3prong)

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AApolpol calculation ( calculation ( mode) mode)left right

MC truth with minimal cuts

Reco distwith

all cuts

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AApolpol calculation ( calculation ( mode) mode) (cont.)(cont.)

±

±

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• Pinu: 1.5% stat. error• Analyzing power is 4.5 times larger if

usingall modes

• Total stat. error estimation = 0.7%

Estimation using analyzing Estimation using analyzing powerpower

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SUSY jet analysisSUSY jet analysis

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SUSY chi1/ne2-pair processSUSY chi1/ne2-pair process

SUSY parameters:m0 = 206 GeV, m1/2 = 293 GeV,tan = 10, A = 0, = 375 GeV

m(±1) = 216.5 GeV, m(0

2) = 216.7 GeVm(0

1) = 115.7 GeV, Others heavy

(e+e- →+1-

1) = 132.2 fb(e+e- →0

202) = 23.3 fb

Degenerate

100 GeV diff.: decays W/Z + LSP　　　　　　　　　　　 (>95%)

5.7 times

BG suppression cuts

• 4-jet clustering (Durham)• # Track >= 20• 100 < Evis < 300 GeV• each Ejet > 5GeV• |cos|jet < 0.99• unlike 3jet (yth,3 > 0.001)• each jet has >= 2tracks• |cos|miss < 0.99• no > 25 GeV leptons

“qqqq + missing”

Loose cut(efficiency ~ 90%)

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Cut plots(1)Cut plots(1)

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Cut plots(2)Cut plots(2)

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Cut statisticsCut statistics

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W/Z mass dist. & kinematic fitW/Z mass dist. & kinematic fitDi-jet mass:

4-momenta Jet の相対角

3 patterns (12&34,13&24,14&23)• All combinations• Best combination

- Combination near W/Z mass- Kinematic fit convergence

Kinematic fit qqqq → 2 jet pairing

Adjust jet energy/directionfor di-jet masses are the sameObservables

1. Cross section - all combinations2. Mass measurement - Kinematic fit - Best combination

(W/Z mass for cut, kinfit conv. for pairing)

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Cross section measurementCross section measurement

↑ all events↓± template ↓0 template

↑ SM background

↓ Fit result

±: 0.64% resolution0 : 2.1% resolution

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Procedure

Mass fitMass fit proceduresprocedures

1. Kinematic fit2. W/Z separation with di-jet mass　→ upper plots3. SM background parametrization

2nd polynomial x Voigt　→ left plot

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Mass fit resultMass fit result

Procedure (cont.)4. SM dist. by toy-MC5. SUSY+SM fit (8 free param.)

Convolution of 2nd pol.& Voigt func. + SM(fixed)integration range of convolutionexpresses edges.

6. Mass by kinematics

Fit resultm(±

1) = 221.7 ± 2.4 GeVm(0

2) = 219.9 ± 0.9 GeVm(0

1) = 118.5 ± 0.8 GeV• Edge fit systematics exist• Much SM bg

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• Tau-pair– Enough cross section / AFB resolution

– ~70% efficiency/purity for decay mode selection

– 1.5% (pinu), 0.7% (combined) stat. errorfor polarization determination (500 fb-1)

• SUSY point5– Separation W/Z is promissing– 1-2GeV SUSY mass determination

SummarySummary

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The endThe end