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AA->HH Study AA->4b analysis & (preliminary) Summary

AA->HH Study AA->4b analysis & (preliminary) Summary. Shin- ichi Kawada ( AdSM , Hiroshima University). Outline. Introduction Previous results Today’s topic AA->4b BG analysis analysis of BG suppression (AA->WW, ZZ, 4b) Summary & Next plan. Introduction.

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AA->HH Study AA->4b analysis & (preliminary) Summary

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  1. AA->HH StudyAA->4b analysis & (preliminary) Summary Shin-ichi Kawada (AdSM, Hiroshima University) 22nd General Meeting @ KEK (2011/9/3)

  2. Outline 22nd General Meeting @ KEK (2011/9/3) • Introduction • Previous results • Today’s topic • AA->4b BG analysis • analysis of BG suppression (AA->WW, ZZ, 4b) • Summary & Next plan

  3. Introduction 22nd General Meeting @ KEK (2011/9/3) Photon Linear Collider (PLC) has been proposed as one of the options of ILC. It is expected that we can observe the Higgs self-coupling in PLC. Feasibility study of Higgs pair creation in PLC is needed.

  4. About PLC ILC : e+ e- collision PLC : gamma-gamma collision Electrons Backward Compton scattering gamma-gamma collision 22nd General Meeting @ KEK (2011/9/3)

  5. Reaction in gamma-gamma collision 4b = b b-bar b b-bar 22nd General Meeting @ KEK (2011/9/3) • Signal : AA->HH->4b • Many backgrounds • AA->WW, ZZ, 4b, etc… • Analysis of background reduction is necessary. • We assumed that Higgs mass equals to 120GeV in this study.

  6. Previous result (1) 22nd General Meeting @ KEK (2011/9/3) • Main backgrounds • AA->WW (~11.6pb, 1.5*107 events/year) • AA->ZZ (~9.42fb, 1.2*104 events/year) • Analysis with Neural Network • We can observe Higgs pair creation if we can develop good b-tagging method and jet clustering.

  7. Previous result (2) optimistic event pessimistic event γ b γ b b-bar : color string b-bar γ b b γ b-bar b-bar 22nd General Meeting @ KEK (2011/9/3) • Other background --- AA->4b • cross-section = 46.6fb (with luminosity & (2-jet invariant mass) < 15 GeV were cut) • ~ 6*104events/year • need the detector simulation & analysis

  8. Topic (1) : AA->4b BG analysis at the 21st General Meeting 4b(opt) : 1.81σ 4b(pes) : 1.47σ not bad, but not enough need more effective cuts/NN analysis • use other useful other parameters • cosθ of jet (cosθ of 2-jet) • event shape (thrust, sphericity, Y-value, etc...) • jet pairing • jet pair of least χH2 -> χH2 , cosθof 2-jet • jet pair of least χA2-> χA2, cosθ of 2-jet 22nd General Meeting @ KEK (2011/9/3)

  9. Analysis procedure (1) input these events to NN 22nd General Meeting @ KEK (2011/9/3) • MC samples • remained events after W filter & Z filter

  10. Analysis procedure (2) 22nd General Meeting @ KEK (2011/9/3) • 17 Input parameters to NN • no relation to χ2 (11 parameters) • visible energy, # of tracks, ycut value of jet clustering, thrust, sphericity, Y-value, cosθ of jet (4), max|cosθof jet| • jet pairing of least χH2(3 parameters) • χH2 , cosθof 2-jet (2) • jet pairing of least χA2(3 parameters) • χA2, cosθ of 2-jet (2)

  11. Result significance (evaluated signal & 4b BG only) 1.92σ 1.43σ 5.59σ Good suppression!! 5.49σ 22nd General Meeting @ KEK (2011/9/3)

  12. Discussion 22nd General Meeting @ KEK (2011/9/3) • Significance (signal v.s. single BG) with cheat jet clustering is good! • signal (cheat) v.s. WW (cheat) : 5.85σ • signal (cheat) v.s. ZZ (cheat) : 5.85σ • signal (cheat) v.s. 4b (optimistic) : 5.59σ • signal (cheat) v.s. 4b (pessimistic) : 5.49σ • try to apply the NN analyses to all events!

  13. Topic (2) : Analysis of BG suppression 22nd General Meeting @ KEK (2011/9/3) • Analysis procedure • pre-selection • W filter (1st NN selection) • 4b filter (2nd NN selection) • Z filter (3rd NN selection) • Cross-section : WW > 4b > ZZ

  14. pre-selection to suppress huge WW BG 22nd General Meeting @ KEK (2011/9/3) • Lorentz factor β2j > 0.05 • |cosθ of 2-jet| < 0.99 • nbj >= 3 • # of b-flavor jets with nsig=3.0 & noffv=1 analysis • nbtj>= 2 • # of b-flavor jets with nsig=3.0 & noffv=2 analysis

  15. Input parameters to NN Details are shown in page24. 22nd General Meeting @ KEK (2011/9/3) • 1st NN selection --- 9 parameters • χH2 , χZ2 , # of b-flavor jet, etc... • 2nd NN selection --- 17 parameters • same as page10 • 3rd NN selection --- 10 parameters • χH2 , χW2 , χZ2, etc...

  16. Cut Summaryreal clustering & 4b (optimistic) PRELIMINARY 22nd General Meeting @ KEK (2011/9/3)

  17. Cut Summaryreal clustering & 4b (pessimistic) PRELIMINARY 22nd General Meeting @ KEK (2011/9/3)

  18. Cut Summarycheat clustering & 4b (optimistic) PRELIMINARY 22nd General Meeting @ KEK (2011/9/3)

  19. Cut Summarycheat clustering & 4b (pessimistic) PRELIMINARY 22nd General Meeting @ KEK (2011/9/3)

  20. (Preliminary) Summary 22nd General Meeting @ KEK (2011/9/3) We can observe the Higgs self-coupling with ~5σ if we use cheat jet clustering. It is possible to measure the Higgs self-coupling in PLC if we can develop good jet clustering algorithm.

  21. Next Plan 22nd General Meeting @ KEK (2011/9/3) • Check the statistical fluctuation • Check/Evaluate the NN systematic error • Now : (training file) = (test file) • Write a paper

  22. Backup slides 22nd General Meeting @ KEK (2011/9/3)

  23. sphericity, Y-value normalized momentum tensor Mab pi : momentum of particle i 3*3 matrix eigenvalue 22nd General Meeting @ KEK (2011/9/3)

  24. Input parameters to NN (details) 1st --- 9 parameters χH2 , χZ2 , visible energy, # of tracks, ycut value of jet clustering, longitudinal momentum, transverse momentum, # of b-flavor jets with nsig = 3.5 & noffv = 1 analysis, # of b-flavor jets with nsig = 3.5 & noffv = 2 analysis 2nd --- 17 parameters same as page10 3rd --- 10 parameters χH2 , χW2 , χZ2 , energy of 2-jet (2), visible energy, # of tracks, longitudinal momentum # of b-flavor jets with nsig = 3.5 & noffv = 1 analysis, # of b-flavor jets with nsig = 3.5 & noffv = 2 analysis 22nd General Meeting @ KEK (2011/9/3)

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