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Search for H->WW in semileptonic decay

Search for H->WW in semileptonic decay. Introduction Higgs Mass reconstruction Search sensitivity at 2fb-1. Ai Mochizuki University of Tsukuba 2007.07.31. j. j. Introduction WW→lνjj decay mode. This channel has 3 times larger statistics than WW→lνlν decay mode

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Search for H->WW in semileptonic decay

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  1. Search for H->WW in semileptonic decay • Introduction • Higgs Mass reconstruction • Search sensitivity at 2fb-1 Ai Mochizuki University of Tsukuba 2007.07.31 summer school2007@FNAL

  2. j j IntroductionWW→lνjjdecay mode • This channel has 3 times larger statistics than WW→lνlν decay mode • We can reconstruct Higgs mass BUT、、、 • Huge QCD/W+2jet Background So, We try to optimize c-tag (Jet probability), kinematics cuts for best sensitivity. summer school2007@FNAL

  3. j j Higgs Mass Reconstruction Evaluated neutrino Pz to reconstruct Higgs mass. M(lepton+nu)=M(W=80.419GeV) 0 solution case  using real part of this solution. two solutions case Which NuPz is better?? We adopt the solution with |NuPz| closer to 0. (We considered 4 methods.) summer school2007@FNAL

  4. hepg level MH=150 NuPz HiggsMass NuPz-hepgNuPz Adopted solution ・all ・correct ・imagunary Discarded solution summer school2007@FNAL

  5. detector level HiggsMass NuPz-hepgNuPz MH=150 jets matched to hard process partons RMS=62.4 49.5(MH=170) 54.4(MH=200) ・all ・correct ・imagunary RMS=27.6 20.6(MH=170) 24.6(MH=200) RMS=60.9 No matching to hepg RMS=50.0 summer school2007@FNAL

  6. Search sensitivity at 2fb-1C-tagging with Higgs Mass reconstruction • Why c-tagging?? • Highly reject the huge W+LF background • Effective background rejection using spin information through • angular correlation summer school2007@FNAL

  7. Event SelectionH->WW->lvcs • One lepton (Pt>20GeV, CEM/PEM/CMUP/CMX) • electron |eta|<2, muon |eta|<1 • Missing Et>20GeV • Two jets with Et>20GeV (level 5), |eta|<2.4 • Cut 1 : C-tagging • Cut 2 : anti heavy flavor-tagging • Cut 3 : kinematic cut ⊿Rls • We didn’t analyze lvud decay mode. summer school2007@FNAL

  8. background purpose : crudely estimate the potential of this search channel. We only consider dominant background. • WW/WZ/ZZ • W+c+jets • W+bbbar • W+ccbar • W+LF summer school2007@FNAL

  9. Cut1 : Charm tagging cut • Aim to identify W->cs decay • Cut at jet probability=0.05 Cut2 : anti HF tagging summer school2007@FNAL

  10. l ν ⊿Rls s c Cut 3 : kinematic cut • Looking at angular distribution in Lab frame. • ⊿Rls is angle between lepton and strange. • ⊿Rls <2.2 summer school2007@FNAL

  11. Signal vs BackgroundHiggs Mass(150GeV) C-tag Before cut ⊿R Anti HF summer school2007@FNAL

  12. Expected number of events before cut summer school2007@FNAL

  13. Expected number of events after all cuts summer school2007@FNAL

  14. Summary&Plans • We developed a tool to reconstruct neutrino Pz. • RMS on reconstructed Higgs mass = 20.6GeV for events with right jet correction,for MH=170 • We performed sensitivity study at 2fb-1 • C-tagging and angular correlation used in event selection. • Challenging channel, our analysis needs improvement. • W+LF background is dominant , while few signal remains after cut. • Need to optimize tag conditions?? Thank you!! summer school2007@FNAL

  15. Expected number of events after all cuts 2fb-1 summer school2007@FNAL

  16. Expected number of events before cut 2fb-1 summer school2007@FNAL

  17. Different Higgs Mass withDetector level HiggsMass NuPz-hepgNuPz ・all ・correct ・imagunary RMS=50.9 MH=170 RMS=45.1 RMS=54.4 MH=200 RMS=45.8 summer school2007@FNAL

  18. back up summer school2007@FNAL

  19. Hepg level correct rate of each method imaginary 4.3% Correct : defined as the case where we pick the solution closer to Hepg(MC truth) Pz MH=150GeV Method3 is best！！ summer school2007@FNAL

  20. introductionHiggsの崩壊過程 ☆MH<135GeV (軽いHiggs) ・lepton,quark pairに崩壊 ・湯川couplingの測定 ☆MH>135GeV (重いHiggs) ・ほとんどがWW/ZZへ崩壊 解析しやすい bb b : 4.2 GeV t : 1.8 GeV c : 1.25 GeV tt cc Higgsは重いものと結合しやすい！ summer school2007@FNAL

  21. introductionHiggsの生成断面積 dominant production LEP Higgsとfermion との結合 湯川couplingに よるHiggsの生成 summer school2007@FNAL

  22. Expected number of events cut1 summer school2007@FNAL

  23. Expected number of events cut2 summer school2007@FNAL

  24. Expected number of events cut1 summer school2007@FNAL

  25. Expected number of events cut2 summer school2007@FNAL

  26. Method3solution1 rate & imaginary rate summer school2007@FNAL

  27. fを真空f0のまわりで展開し、ラグラジアンを求めるfを真空f0のまわりで展開し、ラグラジアンを求める Higgs doubletの4つの自由度 ３つ　⇒　３個の重いベクトルボソンの質量 残りの１つ　　⇒　１個のスカラー粒子(Higgs boson)の質量 質量0のgauge bosonに質量を与えることができた <Higgs boson mass> <Gauge boson mass> gw, g’w : coupling constants summer school2007@FNAL

  28. hadron colliderでのHiggs粒子生成過程 <gluon fusion> <vector boson fusion> jet backgroundが多い Ptが大きいjetが２本 <strahlung off vector bosons> <bremsstrahlung off top quark> ・top quarkの湯川結合 ・backgroundが少ない ・軽いMHには重要な過程 H Tevatronでは 主チャンネル summer school2007@FNAL

  29. search for the signal of a high-mass SM Higgs boson (135 GeV<MH<185GeV) • dominant SM Higgs production ⇒gluon-gluon fusion • dominant Higgs decay ⇒W boson ⇒lepton　１つ+neutrino 1つ or jet ２つ electrons,muons gg->H->WW->lνlν (leptons + neutrinos) summer school2007@FNAL

  30. 具体的には…<hardware triggerの場合> electron muon Pt > 6GeV Eem,t>8GeV Pt > 4GeV Pt > 8GeV summer school2007@FNAL

  31. Event Selection この2つのprimary leptonが必要 • Pt > 20GeV (trigger lepton) • Pt > 10GeV(non-trigger lepton) 　このような２つのleptonを選ぶ ⇒calorimeterやtrackで間違ったjetや重いquarkのsemileptonic decayからのleptonを落とすことができる summer school2007@FNAL

  32. Event Selection <jet veto> <今捜しているchannel> 終状態:lepton２つ＋neutrino2つ no jet <backgroundの一例> jet 終状態:lepton２つ＋neutrino2つ 　　　　　　 ＋jet２つ b l ν l jetをvetoすれば このようなbackgroundは 落とせるはず！ ν b jet summer school2007@FNAL

  33. ところが… • hadron collider大量のgluonが存在 gluon emissionがちょくちょく起こる　 initial state gluon radiation (ISR)のsoft jetはOKとする soft jet summer school2007@FNAL

  34. jet veto ISRが多いため、soft な1jet or 2jet eventも使う • for jet with Et>15GeV, |eta| < 2 ΔR=0.4 ☆number of jet = 0 ☆number of jet = 1 this jet Et< 55GeV ☆number of jet = 2 each jet Et< 40GeV summer school2007@FNAL

  35. ν l+ l- ν Higgs bosonの性質 • Higgs boson: spin 0の粒子 • Higgs decay to WW: WWのhelicityが揃う 終状態でlepton同士、ニュートリノ同士は同じ向きにでやすい φ • large missing Et • small azimuthal angle between leptons • small dilepton invariant mass summer school2007@FNAL

  36. cut後の主なbackgroundDrell-Yan過程 hadron-hadron衝突によるレプトン対の生成 leptonに崩壊するのは、 e,μ,τ τ->ντ+l+νｌ 崩壊にニュートリノを含む Z/ missing Etはない missing Etを持つ summer school2007@FNAL

  37. Conclusion • Searched for • SM Higgs boson production • leptonic decay (proton-anti proton collider at √s=1.96TeV) • no excess was observed • LHCでの期待が高まる！ gg->H->WW(*)->lνlν SM backgroundの期待値とdataはよく一致 Higgs massの関数として σ×BR(gg->H->WW)の95% CL upper limitを設定 summer school2007@FNAL

  38. 資料 • http://www-cdf.fnal.gov/physics/exotic/r2a/20050929.HWW/ • Conference note CDF 7893 • hep-ph/9803257 Electroweak Symmetry Breaking And Higgs Physics • Quarks And Leptons • 素粒子物理学 　　　原康夫　著　　　　　　　　　 summer school2007@FNAL

  39. Introduction <Standard Model> • 1990年代、LEP,Tevatronの実験結果により ☆標準モデル⇒非常に高い精度で検証 ☆力の源⇒ゲージ対称性 summer school2007@FNAL

  40. 大統一理論 電磁力、弱い力、強い力の３つの力の統一 summer school2007@FNAL

  41. Promising channels for SM Higgs(MH <140GeV) summer school2007@FNAL

  42. Promising channels for SM Higgs(MH>140GeV) 今回はこのchannelについて見る summer school2007@FNAL

  43. Signal and SM background expectation summary summer school2007@FNAL

  44. summer school2007@FNAL

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