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Model ID @ 500 GeV

Model ID @ 500 GeV. Taikan Suehara ICEPP, The Univ. of Tokyo. Model ID status. The paper is almost ready Final meeting yesterday Theoretical side – at final draft? 500 GeV study – at final draft LHT is reprocessed (after generator bugfix) Cross section?

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Model ID @ 500 GeV

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  1. Model ID @ 500 GeV Taikan Suehara ICEPP, The Univ. of Tokyo

  2. Model ID status • The paper is almost ready • Final meeting yesterday • Theoretical side – at final draft? • 500 GeV study – at final draft • LHT is reprocessed (after generator bugfix) • Cross section? • 1 TeV study – waiting LHT reprocessing • Saito-san is trapped in M-thesis now • Text will also be improved • In this time – the paper must be submitted very soon!

  3. Three models • InertHiggs • WIMP: hI (scalar) • Visible: h±(scalar) • SUSY • WIMP: c0 (fermion) • Visible: c± (fermion) • LHT • WIMP: AH (vector) • Visible: WH± (vector) All give 2W + 2WIMPfs.

  4. Analysis overview • √s = 500 GeV, 500 fb-1 • full simulation • NO Initial polarization • Use same massesfor all the models m(visible) = 231.57 GeV, m(WIMP)=44.03 GeV • Cross sectionis normalized (200fb & 40fb). • Use W hadronic decay(cut leptonicevents) • Mass-> production angle calculation • Full SM backgroundincluded Weighted to 500fb-1

  5. Event generation • 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 (ILCstandard 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 eg/gg events)

  6. Selection cuts BG suppression cuts “qqqq (non-b) + missing” • 4-jet clustering (Durham) • # Track>=20 • 160 < Evis < 400 GeV • each Ejet > 5GeV • |cosq|jet < 0.99 • unlike 3jet(yth,3 > 0.001) • each jet has >= 2tracks • no > 25 GeVleptons • |cosq|miss < 0.9 • sum |cosq| < 2.6 • sum b-quark prob. < 1 • kinematic fit converged • 65 < mW < 95 GeV

  7. Selection 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

  8. Mass determination • Fitting: 2nd pol. x Voigt x rectangular (9 params) • All 9 params free • Fix 7 params (except edge positions):obtain errors of the edge positions

  9. Mass resolution • Masses (MC: 231.57/44.03) • < 5 % mass resolution for visible/WIMP in 40 fb • < 2 % in 200 fb • Slight difference from MC-truth • Shape effect of the fitting function – can be corrected in real experiment (with template method etc.)

  10. Production angle • 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. • ~30 % of the events arecut out because of negativediscriminant.

  11. 1D distribution • MC & reco have reasonable correlation. • IH-like is different from other two,SUSY-like & LHT-like are similar.

  12. 2D distribution (2 solutions) ~ 10 x statisticsex. SMBG Chi-square can be derived using these distributions.

  13. Chi-square distribution

  14. Separation power results • Good separation with 200 fb cross section • IH-like can be separated also in 40 fb

  15. Threshold scan • Cross section response to beam energy near the threshold reflects spin structure • SUSY has (s-s0)0.5 response whileIH/LHT has (s-s0)1.5 response.

  16. Strategy for threshold scan • Assume 40 fb cross section • 470, 485, 500 GeV with 50 fb-1 stat. each • Previously 470, 500 and 530 • 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 c2 of the fitting • SUSY should give low c2 for n=1/2, high c2 for n=3/2 • Opposite for IH/LH

  17. Chi-square results • Power of 0.5 result shows good separation between SUSY/other two models • Worse than previous (of cource)… Power of 0.5 Power of 1.5

  18. Summary • New physics models can be efficiently separated from background • < 5% mass resolution is obtained for 40 fb signal cross section • Three models can be separated using production angle distribution in 200 fb,and IH-like can be separated from other twoin 40 fb. • Threshold scan can separate SUSY-like and other two in 40 fb

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