Phenomenology of the Higgs Triplet Model by pptfiles

VIEWS: 5 PAGES: 55

									 Testing the custodial symmetry
    in the Higgs sector of the
Georgi-Machacek model 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
                   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 γγ and Zγ decay

• Summary
    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
    Current states of the Higgs search at the LHC
Signal strength (σobs/σSM) in each mode

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

 Hadron Collider Physics Symposium 2012,   Hadron Collider Physics Symposium 2012,
 CMS                                       ATLAS




H → ZZ and H→ WW modes are good agreement to the SM prediction.
     Current states of the Higgs search at the LHC
  Signal strength (σobs/σSM) in each mode

 Hadron Collider Physics Symposium 2012,    Hadron Collider Physics Symposium 2012,
 CMS                                        ATLAS




Obs. H → γγ signal seems to be large compared to the SM prediction.
    Current states of the Higgs search at the LHC
Signal strength (σobs/σSM) in each mode

Hadron Collider Physics Symposium 2012,   Hadron Collider Physics Symposium 2012,
CMS                                       ATLAS




      H → bb and H→ττ modes still have a large uncertainty.
            The SM-like Higgs boson?
• At present, observed new resonance at 126 GeV looks 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→γγ mode
• 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!
Extended Higgs sector
             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
              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 sector              Higgs
Extended Higgswe know the true New physics models
    sector?
      O(100) GeV              Determine        higher than TeV scale
     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 isospin Reps.
   → 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.
  The minimal Higgs Triplet                                        Cheng, Li (1980);
                                                                   Schechter, Valle, (1980);

  Model                                                            Magg, Wetterich, (1980);
                                                                   Mohapatra, Senjanovic, (1981).

                                                                  SU(2)I   U(1)Y     U(1)L
The Higgs triplet field Δ is added to the SM.
                                                          Φ         2       1/2        0
・Important new interaction terms:                          Δ        3         1        -2
                             Lepton number breaking parameter




 ・Neutrino mass matrix


                                              MΔ : Mass of triplet scalar boson.
                                              vΔ : VEV of the triplet Higgs
                 O(0.1) eV          246 GeV
    O(0.1) eV
                                                                 The HTM can be
                  O(1)                O(100) GeV               tested at colliders !!
   The minimal Higgs Triplet                                   Cheng, Li (1980);
                                                               Schechter, Valle, (1980);

   Model                                                       Magg, Wetterich, (1980);
                                                               Mohapatra, Senjanovic, (1981).

                                                              SU(2)I    U(1)Y    U(1)L
 The Higgs triplet field Δ is added to the SM.
                                                       Φ         2       1/2       0
・Important new interaction terms:                       Δ        3        1        -2
                           Lepton number breaking parameter




  ・Neutrino mass matrix


                                           MΔ : Mass of triplet scalar boson.
                                           vΔ : VEV of the triplet Higgs


Non-zero vΔ breaks the custodial symmetry → ρ deviates from unity at the tree level.
We discuss the extension of the HTM to keep the custodial symmetry.
                                                                Georgi, Machacek (1985)

           The Georgi-Machacek (GM) Model
★ The minimal extension of the HTM.                                 SU(2)I   U(1)Y   U(1)L
                                                      HTM   Φ         2      1/2      0
★ Two isospin triplet Higgs fields
                                                 GM         χ         3       1       -2
  are introduced to the SM.
                                                            ξ         2       0       0
★ 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)
                    Decomposition
      Δ:3×3                               Φ:2×2
                 Irreducible decomposition

    5 +3 +1                                  3 +1

                      Mixing (angle β):       Mixing (angle α) :
  5-plet Higgs        Goldston bosons         SM-like Higgs
                      + 3-plet Higgs          + Singlet Higgs


                                                  h, H1


The Higgs bosons belonging to the same multiplet are degenerate
in mass because of the custodial symmetry.
                                Interactions
(Neutrino) Yukawa interaction

                       l                              l                        l
     H5                             H3                       h, H1
          ∝1/sinβ
                       l                              l      ∝cosβ/sinβ
                                                                               l
                                         ∝cosβ/sinβ
(Usual) Yukawa interaction
                                                      f                        f
                                    H3                      h, H1
                                                   f                           f
Gauge interaction
                                           ∝tanβ            ∝cosα/cosβ, sinα/cosβ

                     V                                                         V
     H5                    ∝ sinβ                            h, H1
                      V                                                            V
                                                      ∝ cosβ*cosα, cosβ*sinα
                           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.
                   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:
  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 to gauge boson pairs.
   3-plet Higgs can couple to fermion pairs .

 We focus on the features 2 and 3 in order to identify
 the custodial symmetric GM model at the LHC.
Phenomenology
      Decay of the 5-plet Higgs bosons
                                                 Δm = mH3 – mH5
mH3 = 150 GeV, Δm > 0


         H5++                 H 5+                    H 50




The case of Δm > 0 is the same as the case of Δm=0.
         Decay of the 3-plet Higgs bosons
mH3 = 150 GeV




Δm > 0




Δm < 0
       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.
      4 regions on the vΔ – mΔ plane
★Region I: small vΔ and small mΔ


                                   ・5-plet Higgs decays
                                                  l
                                     H5
                                                  l
                                   ・3-plet Higgs decays

                                                      l
                                     H3
                                                      l
      4 regions on the vΔ – mΔ plane
★Region III: small vΔ and large mΔ


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


                                         ・5-plet Higgs decays
                                                  V             H3
                                    H5             H5
                                                  V             V
                                       ・3-plet Higgs decays
                                                H5              H1
                                    H3             H3
                                                  V             V
      4 regions on the vΔ – mΔ plane
★Region II: large vΔ and small mΔ


                                    ・5-plet Higgs decays
                                                   V
                                      H5
                                                    V
                                    ・3-plet Higgs decays

                                                    f
                                      H3
                                                   f

    We discuss the phenomenology for Region II.
    Production modes for 5- and 3-plet Higgs
       Both                                  5-plet                     3-plet
1. Drell-Yan Process:            3. Vector boson fusion Process    5. Yukawa Process
                 H5 , H3
                                                                                 H3 +

                                                       H5
                 H5 ’ , H 3 ’
2. Mixed Drell-Yan Process:

                H5
                                4. Gauge boson associate Process                        H3 0
                                                      H5
                H3
                                                                                  H3 0 , H 3 +
                                                      V
                                                                                        ,t
    Production modes for 5- and 3-plet Higgs
       Both                                  5-plet                     3-plet
1. Drell-Yan Process:            3. Vector boson fusion Process    5. Yukawa Process
                 H5 , H3
                                                                                 H3 +

                                                       H5
                 H5 ’ , H 3 ’
2. Mixed Drell-Yan Process:

                H5
                                4. Gauge boson associate Process                        H3 0
                                                      H5
                H3
                                                                                  H3 0 , H 3 +
                                                      V
                                                                                        ,t
   Production cross sections




H5++                   H 5+




            H 50
         Production cross sections




      H5++                   H 5+


VBF




                  H 50
             Production cross sections




        H5++                     H 5+


VBF

Associated

                      H 50
           Production cross sections




       H5++                    H 5+




Mixed DY

                    H 50
                      Strategy
                                                                H5
         The VBF and associated processes
H5
                  2 forward jets tagging                        V
                                H5++ may be detected.

            Transverse mass cut + b-jet veto

                                 H5+ and H50 may be detected.

     The mass degeneracy of the 5-plet may be tested.

                The mixed DY process
H5

                   Transverse mass cut
H3


     The mass degeneracy of the 3-plet may be tested.
                        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
               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
                     Δη distributions
Difference of the pseudo-rapidity:
                     Δη distributions
Difference of the pseudo-rapidity:




            Δη > 3.5, (Δη > 4.0 for     event)
                   MT distributions
Transverse mass:
                   MT distributions
Transverse mass:




                    50 GeV < MT < 150 GeV
               Signal and background events
                         (int. luminosity 100 fb-1)




b-jet tagging efficiency: 0.6
            3-plet Higgs reconstructions
★ We use the mixed DY production processes.




5-plet Higgs bosons → diboson decay, 3-plet Higgs bosons → dijet
     Distributions in the mixed DY process




The Δη cut cannot be applied to the mixed DY process,
while the MT cut can be used.
  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.
                        Mjj distributions
★The dijet invariant mass distribution after taking the MT cut:




   The masses of H3+ and H30 may be measured by the peak
   in the dijet invariant mass distribution.
Higgs decays into γγ and Zγ


            +




                              RZγ


      Rγγ
                 Higgs to γγ and 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.
                           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.
Back up slides
Constraint from Zbb vertex
            The electroweak rho parameter
 ★ The experimental value of the rho parameter is quite close to unity.    ρexp ~ 1

Tree-level expression for the rho parameter (Kinetic term of Higgs fields)




                         ρtree = 1         ρtree ≠ 1
      ・ Standard Model
                                               ・ Models with Higgs fields
      ・Multi-doublet                              whose isospin is larger than ½
      (with singlets) model                       e.g., the HTM.
There is the custodial SU(2) sym.                The custodial SU(2) sym. is
in the kinetic term                              broken in the kinetic term.


                              These sector affects
                              the rho parameter by the
Higgs Potential               loop effects.                   Yukawa interaction
                                                                                   12/35
                       Custodial Symmetry
The SM Lagrangian can be written by the 2×2 matrix form of the Higgs doublet:

                                           When we take g’ and yA → 0,
                                           Lagrangian is invariant under SU(2)L×SU(2)R
★ Kinetic term
                                                              ,
                                           After the Higgs field gets the VEV:



★ Higgs potential
                                           this symmetry is reduced to
                                           SU(2)L=SU(2)R =SU(2)V (custodial symmetry).

                                                   SU(2)V breaking by g’ is included in
★ Yukawa interaction (top-bottom sector)           the definition of the rho parameter,
                                                   while that by yA is not.
                                                   There is a significant contribution to
                                                   the deviation of rho = 1 from the
                                                   top-bottom sector by the loop effect.
                                                                                         13/35
Testing an extended Higgs sector at colliders

• Direct way:Discovery of extra Higgs bosons
  Ex. Charged Higgs boson, CP-odd Higgs boson, …


• Indirect way:
Precise measurement for the Higgs couplings
Ex. hhh, hff, hVV
                        Interactions
Yukawa interaction

                    f                       f
    H3          ∝tanβ         h, H1        ∝ cosα/cosβ, sinα/cosβ

                    f                       f

Gauge interaction

                    V                        V
  H5                ∝ sinβ   h, H           ∝ cosβ*cosα, cosβ*sinα
                    V                           V
   5-plet Higgs can (cannot) couple to the gauge boson (fermons).
   3-plet Higgs can (cannot) couple to the fermions (gauge bosons).

								
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