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Top quark spin and interaction in charged Higgs and top quark associated production at LHC Xue Gong 2013.01.04 In collaboration with Z. Si , S. Yang & Y. Zheng arXiv: 1210.7822. Outline. Motivation

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  1. Top quark spin and interaction in charged Higgs and top quark associated production at LHC Xue Gong 2013.01.04 In collaboration with Z. Si , S. Yang & Y. Zheng arXiv: 1210.7822

  2. Outline • Motivation • Charged Higgs production from process and its signatures at LHC • Observables to identify the Htb interaction • Summary

  3. Motivation • Electroweak spontaneous symmetry breaking mechanism (EWSM)  weak gauge bosons and fermions masses & the existence of Higgs bosons in SM EWSM has not been confirmed experimentally • One Higgs-like particle around 126 GeV has been discovered at LHC by ATLAS and CMS Whether it is indeed the SM Higgs boson is still open

  4. Motivation has been predicted by many non-mininal Higgs scenarios , eg. 2HDM,MSSM, LRSM The observation of would : • Be an unambiguous evidence for an extended Higgs vector • Help to unveil the mysteries of EWSB • Further to confirm the identification of Higgs-like boson (126GeV) & distinguish models

  5. Motivation Charged Higgs production channel Kunszt et.al(1992) Gunion et.al(1987), Barnett et.al(1988), Barger et.al(1994), Miller et.al(2000) identify Htb couplings

  6. 2HDM particle content One of the most important feature of all 2HDMs: the existence of charged scalar Higgs Potential: Two Higgs doublet fields: After SSB: 5 physical Higgs scalar left: 2 CP-even 1 CP-odd 2 Charged h0, H0 A0 H±

  7. Theoretical framework 2HDM Lagrangian: Coupling: with

  8. Process at LHC Signal: Background: • Charged Higgs and top quark associated production at LHC • Observables to identify the Htb interaction

  9. Cross section at LHC

  10. Invariant mass distribution To determine charged Higgs mass tan β=30

  11. Cross section of signal and background MadEvent tanβ=30 @ 8 TeV 20 fb-1@ 8 TeV

  12. Cross section of signal and background MadEvent 300 fb-1@ 14 TeV tanβ=30 @ 14 TeV

  13. Angular distribution p.st gagb Top quark spin effect is related to the product of ga and gb Angular distribution of charged lepton :unit 3-momentum of lepton in top quark rest frame : unit 3-momentum of top quark in tH c.m. frame : of lepton in anti-top quark rest frame : of anti-top quark in H- frame 2HDM

  14. Angular distribution >0 =0 <0 Before cuts After cuts After cuts Before cuts

  15. Angular distribution <0 =0 >0 After cuts Before cuts <0 =0 Before cuts >0 After cuts

  16. Predictions of AFB & AFB

  17. Summary • Based on 2HDM, we discussed tH- associated production via at LHC and find that the signal can be distinguished from the background for charged Higgs mass up to 1 TeV or even larger with 14Tev. • Identify Htb interaction from charged lepton angular distribution cosθ and Forward-Backward asymmetry AFB induced by top quark spin which are sensitive to ga gb

  18. Thanks for your attention!

  19. Coupling vs. top spin

  20. Process at LHC

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