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Analysis of 500 GeV Models: Study of Inert Higgs, WIMP, and SUSY Production Angles

This paper presents an in-depth analysis of three theoretical models (Inert Higgs, WIMP, and SUSY) at 500 GeV, focusing on particle production angles and events generated from simulation data. Using a comprehensive dataset of approximately 14 million events, we establish selection criteria for background suppression. The study evaluates cross-section responses and the mass resolution of WIMP particles. Results indicate that effective separation of these models can be achieved even with limited data samples, providing insights for future experimental validations.

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Analysis of 500 GeV Models: Study of Inert Higgs, WIMP, and SUSY Production Angles

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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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