1 / 39

Higgs self-coupling at photon collider (AA->HH Study)

Higgs self-coupling at photon collider (AA->HH Study). Shin- ichi Kawada AdSM , Hiroshima University. Outline. almost same contents @ LCWS11. Motivation Signal & Background Simulation & Analysis Result Summary & Next plan. Motivation.

gwyn
Télécharger la présentation

Higgs self-coupling at photon collider (AA->HH Study)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Higgs self-coupling at photon collider(AA->HH Study) Shin-ichi Kawada AdSM, Hiroshima University 23rd General Meeting @ KEK (2011/11/5)

  2. Outline almost same contents @ LCWS11 23rd General Meeting @ KEK (2011/11/5) Motivation Signal & Background Simulation & Analysis Result Summary & Next plan

  3. Motivation Final goal : measuring Higgs self-coupling constant λ Higgs self-coupling constant in the SM deviation parameter from the SM Before the final goal… We have to investigate the feasibility of measurement of Higgs pair creation in a PLC. 23rd General Meeting @ KEK (2011/11/5)

  4. Optimizing collision energy mH = 120GeV ∫Ldt = 1000fb-1 η = η’ = 1, ηBG = 0 270GeV (GeV)

  5. Beam parameters based on TESLA optimistic parameter x=3.76 in this study

  6. Luminosity distribution simulated with CAIN (GeV)

  7. Signal & Backgrounds γγ->WW γγ->ZZ tt threshold 270GeV

  8. # of events Signal γγ->HH :16 events/year Main backgrounds γγ->WW :1.462*107 events/year γγ->ZZ :1.187*104 events/year γγ->4b :1.37*105 events/year 23rd General Meeting @ KEK (2011/11/5)

  9. Event signature (1) b-jet b-jet mass distribution Mbb (GeV) 23rd General Meeting @ KEK (2011/11/5) • γγ->HH • HH->4b • Mbb = MH (120GeV)

  10. Event signature (2) 23rd General Meeting @ KEK (2011/11/5) • γγ->WW • σγγ->WW ~ 106σγγ->HH • suppressed by b-tagging • γγ->ZZ • ZZ->4b same as HH->4b • discriminate only by mass difference • γγ->4b • Mass distribution is different from signal, but still have events near signal region (~120GeV). • Angular distribution is different from signal.

  11. Simulation & Analysis 23rd General Meeting @ KEK (2011/11/5) • Event generation & Detector simulation • Event reconstruction • jet clustering • b-tagging • nsig method • jet pairing • Event selection • pre-selection • Neural Network (NN)

  12. Event reconstruction (1) information of mass M1, M2 : reconstructed mass i : H, W, Z, bb σ2j : mass resolution ex: χH2 distribution χH2 23rd General Meeting @ KEK (2011/11/5)

  13. Event reconstruction (2) :b-tagging nsig method When there are noffv tracks which satisfy this equation, we regarded this quark as a b-quark. relatively simple b-tagging method can be improved by further study 23rd General Meeting @ KEK (2011/11/5)

  14. Event selection by Neural Network (NN) N : # of events 23rd General Meeting @ KEK (2011/11/5) • 3 steps • W filter • 4b filter • Z filter • Maximize statistical significance

  15. Distribution of NN inputs:WW HH WW HH WW # of b-flavor jet with (nsig = 3.5, noffv = 2) analysis χH2 23rd General Meeting @ KEK (2011/11/5)

  16. Distribution of NN inputs:4b HH 4b HH 4b maximum |cosθ of jet| # of tracks 23rd General Meeting @ KEK (2011/11/5)

  17. Distribution of NN inputs:ZZ HH ZZ HH ZZ χZ2 χH2 23rd General Meeting @ KEK (2011/11/5)

  18. Cut summary (training sample) = (test sample)

  19. Cut summary (training sample) ≠ (test sample)

  20. Further improvement correct color singlet information improve mass resolution, b-tagging efficiency We investigated using generator information for HH, WW, ZZ (not for 4b). 23rd General Meeting @ KEK (2011/11/5) WW BG : almost completely suppressed! 4b & ZZ BG remained Possible improvement --- jet clustering

  21. Improve mass resolution JADE clustering Ex: mass distribution of HH & ZZ BG HH ZZ perfect jet clustering HH ZZ 23rd General Meeting @ KEK (2011/11/5)

  22. Cut summary with perfect jet clustering(training sample) = (test sample)

  23. Cut summary with perfect jet clustering(training sample) ≠ (test sample)

  24. Summary 23rd General Meeting @ KEK (2011/11/5) • We investigated γγ->HH in a gamma-gamma collider based on TESLA optimistic parameters. • Possible to suppress huge backgrounds with improved jet clustering. • Significance ~ 5 with 5 year PLC run • Next plan • Writing a paper -> now updating Ver.0 -> Ver.1

  25. Backup slides 23rd General Meeting @ KEK (2011/11/5)

  26. About PLC Electrons backward Compton scattering gamma-gamma collision 23rd General Meeting @ KEK (2011/11/5)

  27. Comparison of γγ and e+e- process : Higgs self-coupling Contribution of self-coupling is different way. Energy threshold of γγ process is lower than e+e- process. 23rd General Meeting @ KEK (2011/11/5)

  28. γγ->bbbb (4b) events b γ γ b b b : color string b b γ γ b b (2-jet invariant mass) < 15GeV were cut. We assume that we can cut these events. --> 5.872*104 events/year 23rd General Meeting @ KEK (2011/11/5)

  29. Calculation of 4b BG d -> b ELWK = 2 QCD = 2 Calculated with GRACE

  30. Jet clustering JADE clustering pi : 4-momentum of particle i Evis : visible energy Ycut : Ycut value of jet clustering 23rd General Meeting @ KEK (2011/11/5)

  31. Event selection --- pre-selection pre-selection β>0.05, |cosθ|<0.99 more than 3 b-flavor jets with (nsig = 3.0, noffv = 1) analysis more than 2 b-flavor jets with (nsig = 3.0, noffv = 2) analysis β : Lorentz factor of reconstructed particle θ : angle between reconstructed particle and beam axis b-tagging to suppress huge WW BG mainly 23rd General Meeting @ KEK (2011/11/5)

  32. Sphericity, Y-value normalized momentum tensor Mab pi : momentum of particle i 3*3 matrix eigenvalue 23rd General Meeting @ KEK (2011/11/5)

  33. W filter 23rd General Meeting @ KEK (2011/11/5) • 9 input parameters • χH2,χZ2 • visible energy • # of tracks • Ycut value of jet clustering • longitudinal momentum, transverse momentum • # of b-flavor jets (nsig = 3.5, noffv = 1 analysis) • # of b-flavor jets (nsig = 3.5, noffv = 2 analysis)

  34. 4b filter 10 : invariant mass of bb system 23rd General Meeting @ KEK (2011/11/5) • 17 input parameters • no relation to χ2 (11) • visible energy, # of tracks, Ycut value of jet clustering, thrust, sphericity, Y-value, cosθ of jet (4), maximum |cosθ of jet| • jet pairing of least χH2(3) • χH2, cosθ of 2-jet (2) • jet pairing of least χbb2 (3) • χbb2, cosθ of 2-jet (2)

  35. Z filter 23rd General Meeting @ KEK (2011/11/5) • 10 input parameters • χH2, χW2, χZ2 • energy of 2-jet (2) • visible energy • # of tracks • longitudinal momentum • # of b-flavor jets (nsig = 3.5, noffv = 1 analysis) • # of b-flavor jets (nsig = 3.5, noffv = 2 analysis)

  36. Cut summary(training sample) = (test sample)JADE clustering & 4b (optimistic) 23rd General Meeting @ KEK (2011/11/5)

  37. Cut summary(training sample) = (test sample)JADE clustering & 4b (pessimistic) 23rd General Meeting @ KEK (2011/11/5)

  38. Cut summary (training sample) = (test sample)perfect jet clustering & 4b (optimistic) 23rd General Meeting @ KEK (2011/11/5)

  39. Cut summary (training sample) = (test sample)perfect jet clustering & 4b (pessimistic) 23rd General Meeting @ KEK (2011/11/5)

More Related