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Testing the custodial symmetry in the Higgs sector of the Georgi-Machacek model at the LHC

Testing the custodial symmetry in the Higgs sector of the Georgi-Machacek model at the LHC. Kei Yagyu (National Central U). C.-W. Chiang, K Y , arXiv : 1211.2658 [ hep-ph ], t o be published in JHEP. National Taiwan University, 17 th December 2012. Plan of the talk. Introduction

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Testing the custodial symmetry in the Higgs sector of the Georgi-Machacek model at the LHC

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  1. Testing the custodial symmetry in the Higgs sector of the Georgi-Machacekmodel at the LHC Kei Yagyu (National Central U) C.-W. Chiang, KY,arXiv: 1211.2658 [hep-ph], to be published in JHEP National Taiwan University, 17th December 2012

  2. Plan of the talk • Introduction - Current status of the Higgs boson search at the LHC • Extended Higgs sectors - Motivation - The Georgi-Machacek model • Phenomenology - Higgs decays - Higgs productions - Simulation study at the LHC - Higgs to γγand Zγ decay • Summary

  3. Current states of the Higgs search at the LHC ‣The Higgs-like particle has been found at around 126 GeV at the LHC with 5σ. h → γγ h → ZZ* → 4 lepton Historic Milestone but only the Beginning. R. Heuer, July 4th, CERN

  4. Current states of the Higgs search at the LHC Signal strength (σobs/σSM) in each mode Hadron Collider Physics Symposium 2012, ATLAS Hadron Collider Physics Symposium 2012, CMS

  5. Current states of the Higgs search at the LHC Signal strength (σobs/σSM) in each mode Hadron Collider Physics Symposium 2012, ATLAS Hadron Collider Physics Symposium 2012, CMS H → ZZ and H→ WW modes are good agreement to the SM prediction.

  6. Current states of the Higgs search at the LHC Signal strength (σobs/σSM) in each mode Hadron Collider Physics Symposium 2012, ATLAS Hadron Collider Physics Symposium 2012, CMS Obs. H → γγ signal seems to be large compared to the SM prediction.

  7. Current states of the Higgs search at the LHC Signal strength (σobs/σSM) in each mode Hadron Collider Physics Symposium 2012, ATLAS Hadron Collider Physics Symposium 2012, CMS H → bb and H→ττ modes still have a large uncertainty.

  8. The SM-like Higgs boson? • At present, observed new resonance at 126 GeVlooks like the SM-like Higgs boson. (-Consistent with the precision measurements at LEP, - Observed from expected events γγ and ZZ → H is spin 0 or 2) • Large deviation from the SM prediction in H→γγmode • The central value for the H → ττ mode exceeds 0. We need to collect more data in order to clarify the property of the new particle w/126 GeV. Still there are possibilities to consider non-minimal Higgs sectors!

  9. Extended Higgs sector

  10. Why extended Higgs sector? • No principle in the Higgs sector - Negative μ2 term → Just an assumption - Higgs boson as an elementary scalar. → Cause for the quadratic div. in the Higgs mass correction. • Phenomena which cannot be explained in the SM - Neutrino masses - Dark matter - Baryon asymmetry of the Universe

  11. Why extended Higgs sector? • No principle in the Higgs sector →Supersymmetry, Dynamical symmetry breaking, Little Higgs models, … • Phenomena which cannot be explained in the SM - Neutrino masses → Rad. seesaw models, type-II seesaw mechanism - Dark matter → Discrete sym. in the Higgs sector e.g. Inert doublet - Baryon asymmetry of the Universe → Electroweak baryogenesis Predict How can we know the true Higgs sector? Extended Higgs sector New physics models higher than TeV scale O(100) GeV Determine

  12. Basic two constraints from experiments There are hints to determine the structure of the Higgs sector. +0.0017 1. Electroweak rho parameter ρexp =1.0008 -0.0007 Additional doublets or singlets Additional triplets or higher isospinReps. →ρtree= 1 →In general, ρtree≠1 2. Flavor Changing Neutral Current(FCNC) Tree level FCNC processes should be suppressed. Models with multi-doublet structure → There appear tree level FCNCs. ★Additional doublet(s) → FCNC, ★Additional triplet(s) → Rho parameter In this talk, we focus on the possibility that the Higgs sector has triplets.

  13. Cheng, Li(1980); Schechter, Valle, (1980); Magg, Wetterich, (1980); Mohapatra, Senjanovic, (1981). The minimal Higgs Triplet Model The Higgs triplet field Δ is added to the SM. ・Important new interaction terms: Lepton number breaking parameter ・Neutrino mass matrix MΔ : Mass of triplet scalar boson. vΔ : VEV of the triplet Higgs 246 GeV O(0.1) eV The HTM can be tested at colliders !! O(0.1) eV O(100) GeV O(1)

  14. Cheng, Li(1980); Schechter, Valle, (1980); Magg, Wetterich, (1980); Mohapatra, Senjanovic, (1981). The minimal Higgs Triplet Model The Higgs triplet field Δ is added to the SM. ・Important new interaction terms: Lepton number breaking parameter ・Neutrino mass matrix MΔ : Mass of triplet scalar boson. vΔ : VEV of the triplet Higgs Non-zero vΔbreaks the custodial symmetry → ρ deviates from unity at the tree level. We discuss the extension of the HTM to keep the custodial symmetry.

  15. Georgi, Machacek(1985) The Georgi-Machacek (GM) Model ★ The minimal extension of the HTM. HTM ★ Two isospin triplet Higgs fields are introduced to the SM. GM ★ The doublet field and the triplet fields can be expressed as SU(2)L×SU(2)R form: SU(2)R SU(2)L ★ If we take two triplet VEVs are the same: <χ0> = <ξ0> SU(2)L×SU(2)R→ SU(2)V (Custodial Symmetry)

  16. Decomposition Δ : 3× 3 Φ : 2 × 2 Irreducible decomposition 5 + 3 + 1 3 + 1 Mixing (angle β): Goldston bosons + 3-plet Higgs Mixing (angle α) : SM-like Higgs + Singlet Higgs 5-plet Higgs h, H1 The Higgs bosons belonging to the same multiplet are degenerate in mass because of the custodial symmetry.

  17. Interactions (Neutrino) Yukawa interaction h, H1 f l l l f h, H1 H3 H5 H3 ∝1/sinβ ∝cosβ/sinβ ∝cosβ/sinβ f l l l f (Usual) Yukawa interaction ∝tanβ ∝cosα/cosβ, sinα/cosβ Gauge interaction V V h, H1 ∝ sinβ H5 V V ∝cosβ*cosα, cosβ*sinα

  18. Higgs potential ★ The most general SU(2)L×SU(2)R invariant potential: ★ There are 9 parameters in the potential: [m1, m2, μ1, μ2 : dimension full, λ1 – λ5 : dimension less] 2 VEVs : v, vΔ, 4 masses : mH5, mH3, mH1, mh, 1 mixing angle : α and reminding 2 parameters: μ1, μ2.

  19. Decoupling limit The mass formulae (α = 0) In the limit of vΔ →0 (β → 0, M22→ 0) ★ Triplet-like Higgs bosons are decoupled when M12 is taken to be large values. ★There is a relationship among the masses:

  20. Consequences of the custodial sym. 1. Electroweak rho parameter is unity at the tree level → Triplet VEV can be taken to be O(10) GeV. 2. Mass degeneracies among 5- and 3-plet Higgs bosons; mH5++ = mH5+ = mH50 = mH5, mH3+= mH30= mH3 3. Specific interactions; 5-plet Higgs can couple togauge boson pairs. 3-plet Higgs can couple tofermion pairs . We focus on the features 2 and 3 in order to identify the custodial symmetric GM model at the LHC.

  21. Phenomenology

  22. Decay of the 5-plet Higgs bosons Δm = mH3 – mH5 mH3 = 150 GeV, Δm > 0 H5++ H5+ H50 The case of Δm > 0 is the same as the case of Δm=0.

  23. Decay of the 3-plet Higgs bosons mH3 = 150 GeV Δm > 0 Δm < 0

  24. 4 regions on the vΔ – mΔ plane ★Decays of the triplet-like Higgs bosons can be classified into 4 distinctive regions depending on the vΔ and Δm.

  25. 4 regions on the vΔ – mΔ plane ★Region I: small vΔ and small mΔ ・5-plet Higgs decays l l H5 H3 l l ・3-plet Higgs decays

  26. 4 regions on the vΔ – mΔ plane ★Region III: smallvΔ andlargemΔ ・5-plet Higgs decays l H3 H3 H3 H5 H1 H5 H5 l V V V ・3-plet Higgs decays

  27. 4 regions on the vΔ – mΔ plane ★Region IV: large vΔ andlargemΔ ・5-plet Higgs decays H3 H3 H3 H5 H1 H5 V V V ・3-plet Higgs decays V H5 V

  28. 4 regions on the vΔ – mΔ plane ★Region II: largevΔ and small mΔ ・5-plet Higgs decays f H3 f ・3-plet Higgs decays V H5 We discuss the phenomenology for Region II. V

  29. Production modes for 5- and 3-plet Higgs H5, H3 5-plet 3-plet Both 1. Drell-Yan Process: 3. Vector boson fusion Process 5. Yukawa Process H3+ H5’, H3’ H5 H5 2. Mixed Drell-Yan Process: H3 4. Gauge boson associate Process H30 H5 H30, H3+ V , t

  30. Production modes for 5- and 3-plet Higgs 5-plet 3-plet Both 1. Drell-Yan Process: 3. Vector boson fusion Process 5. Yukawa Process H5, H3 H3+ H5’, H3’ H5 H5 2. Mixed Drell-Yan Process: H3 4. Gauge boson associate Process H30 H5 H30, H3+ V , t

  31. Production cross sections H5++ H5+ H50

  32. Production cross sections H5++ H5+ VBF H50

  33. Production cross sections H5++ H5+ VBF Associated H50

  34. Production cross sections H5++ H5+ Mixed DY H50

  35. Strategy The VBF and associated processes H5 2 forward jets tagging H5 H5++ may be detected. H5 Transverse mass cut + b-jet veto H5+ and H50 may be detected. H3 V The mass degeneracy of the 5-plet may be tested. The mixed DY process Transverse mass cut The mass degeneracy of the 3-plet may be tested.

  36. Scenario • mH3 = 150 GeV, mH5 = 140 GeV, vΔ = 20 GeV, α = 0 → Concrete example for Region II • Branching fractions: BR(H5→VV) ~ 100 %, BR(H3+→ cs) ~ 30%, BR(H3+→ τν) ~ 70%, BR(H30→ bb) ~ 90% • We perform the signal & background analysis by using MadGraph5 with the parton level. We consider the hadronic decay of the 3-plet Higgs bosons

  37. 5-plet Higgs reconstructions ★ We use the VBF and associated production processes. Signal Background pp→ W+W+jj, pp→ W+Z jj, pp→ W+W- / ZZ jj, tt

  38. Δη distributions Difference of the pseudo-rapidity:

  39. Δη distributions Difference of the pseudo-rapidity: Δη > 3.5, (Δη > 4.0 for event)

  40. MT distributions Transverse mass:

  41. MT distributions Transverse mass: 50 GeV < MT < 150 GeV

  42. Signal and background events(int. luminosity 100 fb-1) b-jet tagging efficiency: 0.6

  43. 3-plet Higgs reconstructions ★ We use the mixed DY production processes. 5-plet Higgs bosons → diboson decay, 3-plet Higgs bosons → dijet decay

  44. Distributions in the mixed DY process The Δη cut cannot be applied to the mixed DY process, while the MT cut can be used.

  45. Signal and background events(int. luminosity 100 fb-1) After taking the same MT cut, the signal significance can exceed 5 in both the events.

  46. Mjj distributions ★The dijet invariant mass distribution after taking the MTcut: The masses of H3+ and H30 may be measured by the peak in the dijet invariant mass distribution.

  47. Higgs decays into γγand Zγ + RZγ Rγγ

  48. Higgs to γγand Zγ decay RZγ Rγγ ★ Current LHC data of h→γγ mode can be explained when mH5 <~ 150 GeV and mH3 = 150 GeV. ★ Measuring the h→Zγ channel is also important to test the structure of the Higgs sector. (Chiang, KY, arXiv: 1207: 1065[hep-ph]) When Rγγ ~ 1.6, RZγ ~ 1.2.

  49. Summary • The Georgi-Machacek (GM) model is the minimal model included Higgs triplet fields whose Higgs sector is custodial symmetric. • In the GM model, there are the 5-plet, 3-plet and singlet Higgs bosons under the custodial SU(2)V symmetry. • The masses of the Higgs bosons belonging to the same SU(2)V multiplet are the same. • Testing mass degeneracy among the 5-plet Higgs bosons: → The VBF and weak boson associated processes are useful. • Testing mass degeneracy among the 3-plet Higgs bosons: → The mixied DY process is useful after the detection of the 5-plet. The custodial symmetry in the GM model may be tested by above the two steps at the LHC.

  50. Back up slides

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