Higgs decays to γγ and Zγ in models with Higgs extensions

Higgs decays to γγ and Zγ in models with Higgs extensions

Kei Yagyu (National Central U.)

Academia Sinica, September 14th

Collaboration with Cheng-Wei Chiang (National Central U.)

arXiv: 1207.1065 [hep-ph]

Plan of Talk

• Introduction - SM Higgs sector - Current states of the Higgs search at LHC• Extended Higgs sectors• Higgs decays into γγ and Zγ • Summary

Higgs, 希格斯 , ヒッグス• God particle? - Trigger the electroweak symmetry breaking - The Higgs VEV: Unique mass scale (Excepted for ΛQCD) - Origin of Mass: Gauge bosons → Higgs mechanism Quarks & Leptons → Yukawa interaction The “God” really has been discovered at the LHC ??

Higgs sector in the SM

All the masses of particles are given by the Higgs VEV.

V (φ)

φ0φ+

Higgs potential Φ: isospin SU(2) scalar doublet

f +

f 0 F =

Origin of MassGauge boson mass

SU(2)L×U(1)Y → U(1)EM

Higgs VEV

Fermion mass

<F>

<F>

<F>

<F>

F

F

<F>f

f

V

V

g2 y λ

Higgs mass

mV2 = g2v2 mf = y v mh

2 = λv2

Physical state: Only one neutral component h

Higgs sector in the SM

All the Higgs interactions are proportional to the mass

V (φ)

φ0φ+

Higgs potential Φ: isospin SU(2) scalar doublet

f +

f 0 F =

Higgs InteractionGauge interaction

SU(2)L×U(1)Y → U(1)EM

Higgs VEV

Yukawa interaction Self interaction

F

F

F

F

F

F

Ff

f

V

V

g2 y λ

∝ mV2 / v2 ∝ mh

2/v2∝ mf / v

Physical state: Only one neutral component h

Higgs search at collider experiments

Higgs boson

・・・

e+e- (LEP, ILC), pp (Tevatron),

pp (LHC),…

Production Decay

X

Depends on

Collision particle, Center of mass energy, …

Theory(Model)

Theory(Model)

Beam Detector

Detector performance, …

We should know the production and decay property of the Higgs boson.

Branching fraction

hf

f

hW+, Z

W-, Z

hγ, g

γ, g

‣ bb mode: Large branching ratio, but huge background ‣ γγ, ZZ(*) → 4 lepton mode: Tiny branching ratio, but small background

Higgs boson production at the LHC

Gluon Fusion ~ 10 pb

Vector Boson Fusion ~ 1 pb

W/Z association

Top quark association

V. Sharma, talk at Moriond (2011)

‣ The Higgs-like particle has been found at around 126 GeV at the LHC with 5σ.

Historic Milestone but only the Beginning. 　

h → ZZ* → 4 leptonh → γγ

R. Heuer, July 4th, CERN

Current states of the Higgs search at the LHC

Current states of the Higgs search at the LHCSignal strength (σobs/σSM) in each mode

1207.7235 [hep-ex], ATLAS1207.7214 [hep-ex], CMS


H → ZZ and H→ WW modes are good agreement to the SM prediction.



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

H → ττ and H → bb modes have large uncertainty. At CMS, H → ττ mode did not seem to be discovered yet.

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 in H→γγ mode• No observation from H→ττ mode

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

Explanation by extended Higgs sectors• Tiny neutrino masses - The type II seesaw model - Radiative seesaw models (e.g. Zee model)

• Dark matter - Higgs sector with an unbroken discrete symmetry • Baryon asymmetry of the Universe - Electroweak baryogenesis

Introduced extended Higgs sectors

SU(2) doublet Higgs + Singlets, Doublets and Triplets, …

Beyond the SMExtended Higgs sectors Determine

What is the true Higgs sector?There are hints to determine the structure of the Higgs sector.

1. Electroweak rho parameter ρexp = 1.0008

Additional Doublets or Singlets Additional Triplets or Higher isospin reps.→ ρtree = 1 → In general, ρtree ≠ 1

Small triplet VEV or Custodial sym. (Georgi-Machacek model)

-0.0007+0.0017

2. Flavor Changing Neutral Current (FCNC)

Tree level FCNC process should be suppressed.

Extension of Multi-doublets → In general, there appears the FCNC at the tree level.

A discrete Z2 symmetry is often imposed to avoid the tree level FCNC. Glashow, Weinberg

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


We discuss the 2 Higgs doublet model and the Higgs triplet model as important examples.



Two Important examples• 2 Higgs Doublet Model (2HDM) - Many new physics models deduce the 2HDM.

ex. MSSM, Dynamical Sym. breaking models, Radiative seesaw models, and so on.

　 - Source of the CP-violation

• Higgs Triplet Model (HTM) - Tiny neutrino masses can be generated via the type-II seesaw mechanism.

Cheng, Li (1980); Schechter, Valle, (1980); Magg, Wetterich, (1980);Mohapatra, Senjanovic, (1981).

Higgs potential in the 2HDMThe Higgs potential under the softly broken Z2 sym. (Φ1 → + Φ1, Φ2 → -Φ2)

Physical scalar states: 8-3 = 5 Tanβ = v2/v1

Mass formulae (sin(β-α) ~1 )

SM-like Higgs boson Extra Higgs bosons

Goldstone bosons

CP-even Higgs Charged Higgs CP-odd Higgs

　Barger, Hewett, Phillips PRD 41 (1990)

Grossman NPB 426 (1994)

ud

Φ ２

eΦ１u

d

Φ ２

e

ud

Φ ２

e

Φ１

Type-I Type-II (MSSM)

ud

Φ ２

eΦ１

Type-X Type-Y

Four types of the Yukawa interaction

Aoki, Kanemura, Tsumura, Yagyu, PRD 80, 2009

t sb

γW － H －

γ

b t s

Bs → sγ Imposing Z2 symmetry → 　 Only one of the two doublet couples to each fermion.

In the Type-I and Type-X 2HDM, a light charged Higgs boson can be allowed.

CP-odd Higgs (A) decay in the case withsin(β-α) = 1, mA = mH =150 GeV

Type II (MSSM-like) Type X

(μ+)

(μ-)

Kanemura, Tsumura, Yokoya, PRD 85 (2012)

Higgs potential in the HTMThe Higgs potential

Physical scalar states: 10 -3 = 7

NG bosonsDoubly-charged Higgs

CP-even Higgs Singly-charged Higgs CP-odd Higgs

Mass formulae (vΔ/vφ << 1 )Triplet-like

SM-like

A, H

H+

H++A, H

H+

H++

Case I (λ5 >0) Case II (λ5<0)

Mass2 Mass2

Branching ratio of H++

Phenomenology with the mass splitting is drastically different from that without the mass splitting

Without mass splitting With mass splitting (mH++ - mH+ = 10 GeV)

Mass reconstructionqq’ → H++H- → (l+l+ννbb)(jjbb) qq’ → H+H → (l+νbb)(bb) qq → HA → (bb)(bb)

8.0 fb (14 TeV) 2.8 fb (7 TeV)

33 fb 12 fb

130 fb 42 fb

All the masses of the Δ-like scalar bosons may be reconstructed.

vΔ = 10-2 GeV

MT

MT

MT, Minv

mH++ mH+ mH, mA

Signal only

hH, AH+

H++

114 GeV119 GeV130 GeV

140 GeV

Aoki, Kanemura, KY, PRD85(2012)

Higgs decays into the γγ and Zγ


We discuss Higgs decays into the diphoton (hγγ) andthe Z + photon (hZγ).



Higgs to the diphoton channel

The signal strength σOBS/σSM exceeds 1 at the both experiments: 1.56± 0.43 (CMS), 1.9±0.5 (ATLAS).

CMS, ICHEP ATLAS, ICHEP

‣ If this excess is really established, it must be explained by effects of new physics beyond the SM!

We focus on new physics effects to the H → γγ and H → Zγ modes.

h → γγ and h → Zγ decays in the SM‣The hγγ and hγZ verteces are induced at the 1-loop level.

Top quark loop contribution W boson loop contribution

(Z) (Z)

‣Decay rate

Cahn, Chanowitz, Fleishon, (1979); Bergstrom, Hulth, (1985)

Ellis, Gaillard, Nanopoulos, (1976) ;Ioffe, Khoze, (1978); Shifman, Vainshtein, Voloshin, Zakharov, (1979)



(Z) (Z)

‣Decay rate

‣Input parameters: mh = 126 GeV, mt = 173 GeV

Mode Top-loop W-loop Decay rate Branching

h → γγ -1.84 8.38 10.7 keV 0.28 %

h → Zγ -0.643 12.1 7.12 keV 0.18 %

W and top loop effectsare destructive with each other.





(Z) (Z)

‣Input parameters: mh = 126 GeV, mt = 173 GeV

Mode Top-loop W-loop Decay rate Branching

h → γγ -1.84 8.38 10.7 keV 0.28 %

h → Zγ -0.643 12.1 7.12 keV 0.18 %

W and top loop effectsare destructive with each other.

How these predictions are changed by new physics effects?

‣Decay rate



New physics effects to h→γγ(Z) ‣ Any charged new particle which couples to the Higgs boson

can contribute to the h→ γγ and h → Zγ processes.

Spin 0 Spin 1/2 Spin 1

Ex. Charged Higgs boson, Squark, Slepton…

Ex. 4th generation fermion, Chargino… Ex. W’ boson…

(Z)

In this talk, we focus on modes with extended Higgs sector, where new charged scalar bosons are introduced to the SM.

(Z) (Z)

Previous works and our workThere are several papers where the h→γγ mode is studied in an extended Higgs sector.

・ 2 Higgs doublet model

・ Higgs triplet model

・ Zee model (2HDM + charged singlet)

Posch 2011;Arhrib, Benbrik, Gaur 2012;Ferreira, Santos, Sher, Silva 2012

Arhrib, Benbrik, Chabab, Moultakae, Rahilib 2012;Kanemura, Yagyu 2012; Akeroyd, Moretti 2012

Kanemura, Kasai, Lin, Okada, Tseng, Yuan 2000

We study the h→γγ(Z) more comprehensive way in various extended Higgs sectors.

Classes of extended Higgs sectors ‣ 3 classes of extended Higgs sectors.

Class I : Models with one singly-charged scalar boson

Class II : Models with one singly-charged and one doubly-charged scalar boson

Class III : Models with two singly-charged scalar bosons

Ex. 2HDM

Ex. Higgs triplet model, Zee-Babu model

Ex.: Radiative seesaw models (Zee model, Kauss-Nasri-Trodden model, Aoki-Kanemura-Seto model)

SM H±

SM H± H±±

SM H1± H2

±

List of models

‣ We consider Higgs sectors with additional SU(2)L singlets (S), doubles (D) and triplets (T).

Class I Class II Class III

Singlet

Doublet

Triplet

There are 13 models depending on the # of scalar fields.

(Y = 1)

(Y = 2)

(Y = 1/2)

(Y = 0)

(Y = 1)

SM-like Higgs boson ‣ We assume the SM-like Higgs boson (h): -The Yukawa coupling (hff) and the gauge coupling (hVV) is the same as those in the SM.

Same as the SMOnly h→γγ and h→Zγ decay modes can be modified significantly. The other decay rates are almost the same as the SM.

h

・・・Production Decay

X

Modified decay rate directly affects to the number of events.

Modified decay rates ‣ Decay rates are modified by new contributions from charged scalar bosons:

‣ The Higgs couplings with charged scalars (λSSh) and the Z boson (gSSZ) can be defined as

Points

1. Decay rate of h→γγ is enhanced when λSSh is negative.

suppressed when λSSh is positive.

2. Decay rate of h→ Zγ depends on the isospin (I3) of the scalar boson.

Measuring both h→γγ and h→Zγ would be a useful tool to determine the true Higgs sector.

Relevant terms in Class I and II

⊃

⊃

Φ : SM doublet

: Extra scalar field1, 2

Relevant terms in Class III

M1 = M2 = M3

= M

M1 = M2 = M3

= M

Mixing angle:⊃=

≠

Results (Class I and Class II)

Class I

Class II

ΔB (h → X) = [Br(h → X)NP - Br(h → X)SM]/ Br(h → X)SM

mH+ = mH++ = 200 GeV

Not allowed by the vacuum stability bound.

Results (Class I and Class II)

Class I

Class II

R = Br(h → Zγ)NP/ Br(h → γγ)NP

mH+ = mH++ = 200 GeV

Not allowed by the vacuum stability bound.

Results (Class III)mH1+ = 200 GeV, mH2+ = 300 GeV, M = 308 GeV ΔB (h → X) = [Br(h → X)NP - Br(h → X)SM]/ Br(h → X)SM

Results (Class III)mH1+ = 200 GeV, mH2+ = 300 GeV, M = 308 GeV

R = Br(h → Zγ)NP/ Br(h → γγ)NP

Summary• To know the true Higgs sector → To determine physics beyond the SM.1. Direct way : Discovery extra Higgs bosons Decay of the extra Higgs is important to discriminate each Higgs sector. -Type-II 2HDM: qq → HA → 4b, Type-X 2HDM: qq → HA → 4τ, 2τ + 2μ - Decay of H++ in HTM: H++ → l+l+ (Small vΔ), H++ → W+W+ (Large vΔ), H++ → H+W+ (Large mass splitting). 2. Indirect way: Precise test of the Higgs couplings (hγγ and hZγ) 　 h → γγ and h → Zγ decay modes are sensitive to the new physics models. 　　　　→ Measuring both modes may be useful.　　　 We focused on effects of charged scalar boson which are introduced from various extended Higgs sectors. Class I: H±, Class II: H± + H±±, Class III: H1

± + H2±

　　　 When a charged scalar mass is taken to be around 200 GeV, h → γγ can be enhanced ~ 15 % , ~ 80 % and ~ 30 % in Class I, II and III, respectively compared with the SM prediction.

Scalar loop function

Potential in models Class III

In models w/ φSM + S1+ + S2

+, φSM + D1 + D2, φSM + T10 + T2

0 , μ is absent.

In models w/ φSM + D + S, φSM + D + T0, M3 and λ3 are absent.

Heavy case (mS = 400 GeV )

Class I

Class II

Measurement hZγ coupling at linear colliders

Dubinin, Schreiber, Vologdin, Eur. Phys. J. C30 (2003)

h → Zγ decay process has been analyzed via the vector boson fusion process at the future linear collider.

mh = 120 GeV, root(s) = 500 GeV, integrated L = 1 ab-1

Accuracy of ΔBR (h → Zγ) is expected to be 48 %By using polarized beam, this would be improved to be 29 %.

Branching ratios of H+, H and A

★ The H+ → f0 W+ mode can be dominant in the case of Δm ≠ 0.

★ The f0 → bb mode can be dominant when vΔ > MeV.

CP-even Higgs decay in the case withsin(β-α) = 1, mA = mH =150 GeV

Type II (MSSM-like) Type X

Kanemura, Tsumura, Yokoya, PRD 85

Type-X 2HDM simulation

b→sγ

Type-I, X

Type-II, Y

t sb

γW －

H －

γ

b t s

Barger, Hewett, Phillips PRD 41 (1990)

Higgs decays to γγ and Zγ in models with Higgs extensions

Documents

Transcript of Higgs decays to γγ and Zγ in models with Higgs extensions