Model ID @ 500 GeV

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Taikan Suehara, 16 th general meeting of ILC physics (Asia) wg., 2010/07/17 page 1 Model ID @ 500 GeV Model ID @ 500 GeV Taikan Suehara ICEPP, The Univ. of Tokyo

description

Model ID @ 500 GeV. Taikan Suehara ICEPP, The Univ. of Tokyo. Three models. Inert Higgs WIMP: h I (scalar) Visible: h ± (scalar) SUSY WIMP: c 0 (fermion) Visible: c ± (fermion) LHT WIMP: A H (vector) Visible: W H ± (vector). All give 2W + 2WIMP fs. Analysis overview. - PowerPoint PPT Presentation

Transcript of Model ID @ 500 GeV

Page 1: Model ID @ 500 GeV

Taikan Suehara, 16th general meeting of ILC physics (Asia) wg., 2010/07/17 page 1

Model ID @ 500 GeVModel ID @ 500 GeV

Taikan SueharaICEPP, The Univ. of Tokyo

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Taikan Suehara, 16th general meeting of ILC physics (Asia) wg., 2010/07/17 page 2

1. Inert Higgs– WIMP: I (scalar)

– Visible: ± (scalar)

2. SUSY– WIMP: 0 (fermion)

– Visible: ± (fermion)

3. LHT– WIMP: AH (vector)

– Visible: WH± (vector)

Three modelsThree models

All give 2W + 2WIMP fs.

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• √s = 500 GeV, 500 fb-1

• full simulation• NO Initial polarization• Use same masses for all the models

m(visible) = 231.57 GeV, m(WIMP)=44.03 GeV

• Cross section is normalized (200fb & 40fb).• Use W hadronic decay (cut leptonic events)• Mass -> production angle calculation• Full SM background included

Weighted to 500fb-1

Analysis overviewAnalysis overview

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ILDILD detector &detector & frameworkframework

ILD detector (ILD00)• Vertex: Si pixel (3x2 layers)• Silicon Tracker: 4 layers• TPC(main tracker)• ECAL (0.5x0.5 cm tile, Si/W)• HCAL (3x3 cm tile, Sci/Fe)• Solenoid (3.5Tesla)• Muon detector

Event generation(signal, SM background)

Full-MC simulation(GEANT4)

Hit, MC info(LCIO file)

Event reconstructi

on

• Tracking• Particle Flow• Flavor tagging etc.

Analysis

Stdhep event files

Particle information (ROOT tree)

• Event weighting• Separation cuts• Analysis (mass, angle…)

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• Signal: JSF/physsimStructure

• HELAS for helicity amp. calculation• BASES for numerical integration• SPRING for event generation

– Pythia for quark fragmentation

– ISR/Beamstrahlung included– ~0.1 M events for each process generated

• Background: SLAC (ILC standard sample)– whizard/pythia for all SM processes– ~14 M events in total (80-200 fb-1 for 2/4/6

fermion events, 0.1-1 fb-1 for e/ events)

Event generationEvent generation

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Selection cutsSelection cuts

• 4-jet clustering (Durham)• # Track >= 20• 160 < Evis < 400 GeV• each Ejet > 5GeV• |cos|jet < 0.99• unlike 3jet (yth,3 > 0.001)

“qqqq (non-b) + missing”

• each jet has >= 2tracks• no > 25 GeV leptons• |cos|miss < 0.9• sum |cos| < 2.6• sum b-quark prob. < 1• kinematic fit converged• 65 < mW < 95 GeV

BG suppression cuts

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Selection efficiencySelection efficiency

• IH eff: 59.8%, pur (200 fb): 78.6%, pur (40 fb): 42.3%• SUSY eff: 58.3%, pur (200 fb): 77.7%, pur (40 fb): 41.0%• LHT eff: 58.9%, pur (200 fb): 78.2%, pur (40 fb): 41.8%

Acceptable selection performance

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W energy distribution (for W energy distribution (for mass)mass)

MC truth (signal only)

Reco (kin-fitted)MC & reco have a good correlation.Difference of shapes (esp.WH) is notused for the discrimination in this analysis.

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Mass determinationMass determination

Fitting: 3rd polynomial x Voigt function (10 params)

1.All 10 params free2.Fix 8 params (except edge positions):obtain errors of the edge positions

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• Edge positions from the fit: (MC: 96.32/174.78)

• Masses (MC: 231.57/44.03)

Mass resolutionMass resolution

Low edge(200 fb)

High edge(200 fb)

Low edge(40 fb)

High edge(40 fb)

IH 97.00 ± 0.13 GeV

174.22 ± 0.19 GeV

97.86 ± 0.38 GeV

176.22 ± 0.84 GeV

SUSY 97.12 ± 0.15 GeV

173.46 ± 0.21 GeV

96.10 ± 0.54 GeV

176.02 ± 0.85 GeV

LHT 96.94 ± 0.16 GeV

174.39 ± 0.10 GeV

99.56 ± 0.48 GeV

174.67 ± 0.34 GeV

Visible(200 fb)

WIMP(200 fb)

Visible(40 fb)

WIMP(40 fb)

IH 232.28 ± 0.12 GeV (0.12)

43.41 ± 0.58 GeV (0.57)

232.40 ± 0.37 GeV (0.39)

35.42 ± 2.78 GeV (2.23)

SUSY 232.59 ± 0.13 GeV (0.14)

44.84 ± 0.63 GeV (0.64)

231.04 ± 0.51 GeV (0.50)

41.64 ± 2.63 GeV (2.50)

LHT 232.18 ± 0.13 GeV (0.13)

43.18 ± 0.52 GeV (0.50)

234.06 ± 0.35 GeV (0.41)

33.91 ± 2.07 GeV (1.56)

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• Production angle of the visiblenew particle can be calculatedfrom W directions with massesof new particles andback-to-back assumption.

• The angle has spin info.but two-fold ambiguity (solution of 2nd equation) exists.

Production angleProduction angle

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• The distribution looks reasonable.• ~30% of the events cannot be used.

(discriminant > 0 events selected)

Discriminant distributionDiscriminant distribution

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• MC & reco have reasonable correlation.• Three models seem to be

discriminated.

1D distribution1D distribution200fb

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2D distribution (2 solutions)2D distribution (2 solutions)

SUSYIH

LHT SMBG

Chi-square can be derived using these distributions.

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• Powerful for larger templates• Confirmed by comparing “same” model but statistically

independent samples– Uncertainty exists with finite statistics

reflects the statistical fluc. of templates between Di and Ti

Separation powerSeparation power

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• Good separation with 200 fb cross section

• Nearly 3 separation with 40 fb• IH/SUSY has better separation

– Consistent with intuitive view

Separation power resultsSeparation power results

Uncertainty from statistics : ~2Uncertainty from statistics : ~.3

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• Uncertainty of masses can cause uncertainty on the angular distributions

• We are examining such effects by simulation with shifted masses (full or generator level)

Effect of mass measurementEffect of mass measurement

IH 40fb IH 200fb

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• With full simulation, no significant deviation can be seen between shifted and original samples(within MC statistics…)– Higher statistics with all shifted masses is not

practical

• Generator analysis has not been finished…– Need to ‘adapt’ the MC distributions to reco

ones… (with some coefficients)– Uncertainty of that adaptation should be also

investigated…

Results…Results…

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• Cross section response to beam energy near the threshold reflects spin structure– SUSY has (ECM-ETH)0.5 response while

IH/LH has (ECM-ETH)1.5 response.

Threshold scanThreshold scan

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• Assume 40 fb cross section• 470, 500, 530 GeV with 50 fb-1 stat. each• Threshold energy is treated unknown• SM bg and signal efficiency is assumed

to be the same as 500 GeV• Toy-MC with 3-point fittings

• Examine 2 of the fitting– SUSY should give low 2 for n=1/2, high 2 for n=3/2– Opposite for IH/LH

Strategy for threshold scanStrategy for threshold scan

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• Power of 0.5 result shows good separation between SUSY/other two models

Chi-square resultsChi-square results

Power of 0.5 Power of 1.5

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• Analysis almost finished– Cut optimization / mass fitting– Model ID with 2d angular distribution

• Some work left in the mass shift analysis

– Threshold scan

• Paper writing is ongoing (at final round?)– LCWS proceedings for both theory and 500

GeV experiment (this work) are already available

– Need consistency between 500 GeV and 1 TeV work

Summary/statusSummary/status