2HDM and chiral U(1)′ models - Yonsei...

2HDM and chiral U(1)′ models

1

Chaehyun Yu (KIAS)

Yonsei University, May 14, 2013

Based on Phys. Lett. B 717, 202 (2012);

EPJC 73, 2269 (2013);

JHEP 1303, 151 (2013).

with P. Ko (KIAS) and Yuji Omura (TUM)

2

• Higgs mechanism in the SM

Outline

• Chiral U(1)′ models

• Two Higgs doublet models with Z2 symmetry

• Phenomenology

- Top forward-backward asymmetry

- B→D(*)τν and B→τν

• Conclusions

• Two Higgs doublet models with spontaneous Higgs symmetry breaking

3

Introduction • A Higgs-like scalar boson with 125 GeV was discovered at LHC.

- a SM Higgs boson?

- exist extra Higgs bosons?

• Multi-Higgs scenario may be motivated by SUSY or GUT, etc.

- FCNC, gauge anomaly, stable charged particle,…

• two Higgs doublet models and chiral U(1)′ models.

4

Higgs mechanism in SM • generate particle masses in an SU(2)XU(1) gauge invariant way.

• three d.o.f masses for MW and MZ.

• fermion masses can be generated by using the same .

• resolve the unitarity problem in the SM.

5

Problems in SM • Hierarchy problem or naturalness problem.

• stability problem.

6

Stability of vacuum

7

New Physics extends Higgs sector

8

2HDM • One of the simplest models to extend the SM.

• Two doublets of SU(2) : 8 d.o.f. → 3 gauge boson masses+5 physical

Higgs bosons.

9

Two Higgs Double Model

• In general, the models with many Higgs suffer from Flavor changing

process.

mass matrix

neutral Higgs h coupling

• In general, each doublet couple to the SM fermions.

- type III or general 2HDM.

10

Two Higgs Double Model

• Flavor changing neutral current (FCNC).

11

• A simple way to avoid FCNC problem is to assign an ad hoc Z2

symmetry.

Z2 symmetry

→ Natural Flavor Conservation (NFC).

12


symmetry.

Z2 symmetry

S.L.Glashow, S.Weinberg, PRD15, 1958 (1977);V.D.Barger, J.L.Hewett, R.J.N.Phillips, PRD41, 3421 (1990); M.Aoki, S.Kanemura, K.Tsumura, K.Yagyu, PRD80, 015017 (2009).

• Type I :


Each sector (mass matrices) depends on one Higgs (VEV).

13


symmetry.

Z2 symmetry

• Type II :



14


symmetry.

Z2 symmetry

• Type III :



15


symmetry.

Z2 symmetry

• Type IV :



16

• It is well known that discrete symmetry could generate a domain wall

problem when it is spontaneously broken.

Generic problems of 2HDM

• Usually the Z2 symmetry is assumed to be broken softly by a dim-2

operator, term. †

1 2H H

17

2HDM with spontaneous Higgs Symmetry breaking

propose to replace the Z2 symmetry in 2HDM by a new U(1)H symmetry

associated with Higgs flavors.

• H1 and H2 have different U(1)H charges.

• no domain wall problem.

• Higgs signal will be changed by new U(1)H gauge boson ZH.

• Good CDM candidates will be naturally added.

• The origin of such a discrete symmetry is not clear at all.

18

• Higgs interacts with ZH.

Higgs sector

mass base

Z and ZH mix at the tree level.

SM

19

• could give the bound on the tree-level mixing.

ρ parameter

• In the 2HDM with U(1)H,

• Compared with the experimental value

• large mZH or small tanβ (for h1=0) is favored.

20

Gauged U(1)H

Potential in typical 2HDM

Source of pseudo-scalar mass Z2 odd

Good answer for FCNC and those problems is

massless eaten

Explicit Z2 may be required to avoid domain wall and light extra scalar scalars

light gauge boson (ZH)

required (?)

21

• is gauge-invariant if .

2HDM with U(1)H

†

1 2H H 1 2h h h

Source of pseudo-scalar mass

• is forbidden if . †

1 2BH H 1 2h h

• If not gauged with the extra U(1)H, encounter the usual problem of a

massless pseudoscalar.

• The massless mode is eaten by ZH.

• The scalar spectrum is different from the usual 2HDM.

2 2

5 / m

22

Z2→gauged U(1)H extension

• very naïve assignment

23

Type-I 2HDM

• Only one Higgs couples with fermions.

• anomaly free U(1)H with RH neutrino.

There appear an infinite number of new models.

24

Type-I 2HDM



25

Type-I 2HDM



• SM fermions are U(1)H singlets.

• ZH is fermiophobic and Higgphilic.

• is the main source of production and discovery of ZH. HH W Z

26

Type-I 2HDM



• U(1)H=U(1)B-L.

• ZH gets its mass from H2 (and also by Φ).

• different from the usual (B-L) model, where U(1)B-L is broken by Φ.

27

Type-I 2HDM



• U(1)H=U(1)R.

• ZH couples only to the RH fermions.

• the would-be SM Higgs doublet H1 also carries nonzero U(1)H charge.

28

Type-I 2HDM



• U(1)H=U(1)Y.

• different from the SM because h1=1/2≠0 (in SM, h1=0).

N.B. vectorlike U(1)B or U(1)L : anomaly free with extra chiral fermions.

29

Type-II 2HDM

• H1 couples to the up-type fermions, while H2 couples to the down-type

fermions.

• Requires extra chiral fermions for cancellation of gauge anomaly.

3(1)HU

2(1) (1)Y HU U

Two SM vector-like pairs

1 2

0 0 0 0 0

R R L R RU D Q L E N H H

u u u

30

Type-II 2HDM

• The mass terms of extra fermions are given by .

• forbid mixing terms which may cause FCNC such as

for .

or ij Li Rj ij Li Rjm q U q U ˆ ˆ, , 0,R R RQ Q n u

Extra fermions become stable ....

31

CDM in Type-II 2HDM

or

SU(2) doublet case SU(3) triplet case

U(1)H forbids the mixing with SM fields

U(1)H forbids the mixing with SM fields

stable charged and neutral stable colored particles

radiative corrections make charged heavier and

neutral becomes CDM

adding U(1)H charged scalar, X †

1 2i Ri L i Ri LX D q XD q

X is CDM

1 2 1, , 0 and 0,2 2

u d u dq h e l n h q u d h e n

32

Type-II,-III,-IV 2HDMs

• In Tyep-II case, possible to make the leptophobic Z′ model in the

context of E6.

- could generate the mixing terms between the SM fermions and the

extra fermions at tree level.

- the Yukawa couplings must be tuned.

• Type-IV case could be realized by nonzero u=e≠0.

• Type-III case: may be leptophobic or leptophilic models by

33

Phenomenology

• the phenomenology would differ model by model.

• a new channel is

h h

Z

ZH ZH

ZH

Contribute to Z boson mass.

<H> <H> h

ZH

ZH

Z Z Z Z X X

34

Minimal flavor violation

• might be a guideline for new physics.

• all flavor violating and CP-violating transitions are governed by the CKM

matrix and the only relevant local operators are the ones that are relevant

in the SM → Minimal flavor violation (MFV).

• new physics scale ~ a few TeV.

• 2HDM respects this hypothesis.

• the excellent agreement of flavor data with the SM predictions.

• If there exist experimental results with large flavor violation, MFV must

be broken.

35

Chiral U(1)′ model

• necessary to generate large FCNCs for the discrepancies without

conflict with experiments.

• extension of 2HDM with spontaneous Higgs symmetry breaking.

• slightly breaks the 2HDM with spontaneous Higgs symmetry breaking.

• difficult to assign flavor-dependent charges to down-type quarks due to

the strong constraints from FCNC experiments → assign U(1)′ charges

only to right-handed up-type quarks (flavor-dependent).

36


37


• consider a gauge boson of U(1)′ : Z′

• Z′ is leptophobic : avoid the LEP II and Drell-Yan bounds.

• a flavor-dependent leptophobic U(1)′ : anomalous.

- introduce additional fermions to cancel the gauge anomalies.

• exists a candidate of cold dark matters.

• Higgs sector must be extended to construct a realistic Yukawa interactions.

• Yukawa interactions : additional Higgs fields are inevitable.

• Both Z′ and Higgs fields affect the top AFB and charge asymmetry.

• Charged Higgs bosons contribute to B physics.

38

• U(1)′ charged Higgs fields generate the Z′ boson mass.

Why need additional Higgs?

• If there is no Higgs fields charged under U(1)′, the top quark would be

massless.

• similar to the WLWL scattering in the intermediate vector boson model.

- restores unitarity with U(1)′ charged Higgs fields.

• also true in the W′, axigluon, and any other models if a new spin-1

particle has a chiral U(1)′ charge.

39

• Charge assignment : SM fermions

Left-handed quarks and right-

handed down-type quarks have

universal couplings.

Flavor-dependent

Higgs


40

• Charge assignment : Higgs fields

• The U(1)′ is spontaneously broken by U(1)′ charged complex scalar Φ.

• introduce three Higgs doublets charged under U(1)′ in addition to H

uncharged under U(1)′.


41

• Anomaly cancelation requires extra fermions I: SU(2) doublets

one extra

generation

vector-like

pairs

SU(2)L2∙U(1)′

U(1)′ 2∙U(1)

a candidate for CDM


42

• Anomaly cancelation requires extra fermions II: SU(3)c triplets

a candidate for CDM

• introduce the singlet scalar X to the SM in order to allow the decay of

the extra colored particles.


43

• 2 Higgs doublet model :

∝ the fermion mass

1 2 3( , , ) (0,0,1)u u u


44

• 3 Higgs doublet model: 1 2 3( , , ) ( ,0, )u u u q q


45

• Gauge coupling in the mass base

- Z′ interacts only with the right-handed up-type quarks

- The 3 X 3 coupling matrix is defined by

biunitary matrix diagonalizing the up-type quark mass matrix


46

• Yukawa coupling in the mass base (2HDM)

- lightest Higgs h:

- lightest charged Higgs h+:

- lightest pseudoscalar Higgs a:


47

• Our models are

so-called type-III-like 2HDM (3HDM),

where Yukawa couplings are controlled by gauged U(1) symmetry.

There are tree-level FCNCs.


- large (t,u) of scalars, Z′ → enhance the top AFB

, , ,Z h H a Z

- O(1) (t,u) coupling is required to achieve a large top AFB

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• Tevatron

forward

backward

Top AFB at the Tevatron

• AFB is generated by the difference in top and anti-top distributions.

q

q

- an incident quark repels the top quark, while it attracts the anti-top

quark.

- an incident anti-quark repels the anti-top quark, while it attracts the top

quark.

• QCD Coulomb interaction

49

• LHC

q

q

Top charge asymmetry at LHC

• Charge asymmetry is generated by the shape difference in distributions.

q

q in the parton rest frame

50

Top AFB at Tevatron in ~5 fb-1

~ 2σ

~ 2σ No conclusive evidence for the dependence of top AFB on the ttbar invariant mass.

51

Top AFB at CDF in 8.7 fb-1

~ 2σ

52


CMS-PAS-TOP-11-030

ATLAS, 1203.4211

SM prediction at MC@NLO : 0.006 0.002CA

0.004 0.010 0.012CA

0.018 0.028 0.023CA

53


• No tendency in distribution. ttm

• compatible with the prediction from MC@NLO.

54

History of AFB in the SM

• AFB in the b, t quark production in QCD : Halzen, Hoyer, Kim, PLB195

(1987).

• detailed QCD calculation at NLO : Kuhn, Rodrigo, PRL81 (1998).

- 4~5% at the Tevatron.

• update the previous analysis: Kuhn, Rodrigo, PRD77 (2008).

- at the Tevatron.

• NLO+NNLL accuracy: Ahrens, Ferroglia, Neubert, Peciak, Yang, PRD84

(2011).

• EW contributions at NLO: Hollik, Pagani, PRD84(2011); Kuhn, Rodrigo,

JHEP1201.

5.1 0.6%

NLO

NLO+NNLL

CDF lep+jets

55

FB

ttAFB( 450 GeV)tt

ttA M FB( 450 GeV)tt

ttA M

0.67

0.547.14

1.05

0.687.16

0.4

0.45.3

0.8

0.65.2

1.0

0.610.4

1.7

0.910.8

47.5 11.211.6 15.3

Ahrens,Ferroglia,Neubert,Pecjak,Yang,PRD84

15.8 7.5

(In units of %)

SM prediction at NLO+NNLL

56

Kühn, Rodrigo, JHEP1201 • reanalyze electromagnetic as well as weak corrections.

- enhancement of AFB by about a factor 1.1.

• restrict the system to a transverse momentum < 20 GeV.

- enhancement of AFB by factors between 1.3 and 1.5.

tt

SM(NLO+EW)

MCFM(NLO)

CDF lep+jets

FB

ttAFB( 450 GeV)tt

ttA M FB( 450 GeV)tt

ttA M

8.7 1.0

5.8 0.9 4.0 0.6

12.8 1.1

8.8 1.3

47.5 11.211.6 15.3

6.2 0.4

15.8 7.5

(In units of %)

EW contributions in the SM

57

tt

TP

• D0 disagrees with MC@NLO.

• changes sign at ~ 20 GeV.

• disagreement between MC

generators.

• the asymmetry would be

enhanced if the data are lost

at high pT.

dependence D0, PRD84 ,112005(2011)

60

• flavor dependent.

• challenging to

construct a realistic

model.

- anomaly free,

renormalizable,

realistic Yukawa

couplings.

, ,Z W

New physics models for top AFB

61

General remarks on new models

• σth in new physics models must be close

to σexp.

• int quad. in new physics

• no evidence for a resonant state between

350 GeV and 1.5 TeV (model-dependent).

• required to produce a large AFB.

• the exotic decay of the top quark must be

suppressed.

62

Models with s-channel exchange

• requires couplings to both

and .

• axigluon, KK gluon, and etc.

5q qG

5t tG

• strongly constrained by dijet production,

where no resonant states have been

observed.

- small couplings to the light quarks.

- large coupling to the top quarks.

• LHC limits for top resonance could be

problematic.

• light gluon with a large decay width?

Ferrario, Rodrigo, PRD78; PRD80; Frampton, Shu, Wang, PLB683; Bai, Hewett, Kaplan, Rizzo, JHEP1103

63

Models with t-channel exchange

• Z′, W′, or scalar exchanges with large flavor

changing neutral currents.

• could not be constrained by dijet production

and top resonance searches.

• usually assume that only one off-diagonal

coupling to the top quark is relevant.

- can be realized in a complete model?

• severely constrained by the

same sign top pair production.

- the t-channel scalar exchange

model has a similar constraint.

64

Z’ model

• assume large flavor-offdiagonal coupling and

small diagonal couplings.

• In general, could have different couplings to

the top and antitop quarks.

• light Z′ is favored from the Mtt

distribution.

Jung, Murayama, Pierce, Wells, PRD81

65

Same sign top pair production at LHC

CMS: σ(pp→tt( j))<17 pb at 95C.L. ATLAS: σ(pp→tt( j))<2 pb at 95C.L.

CMS, JHEP1108; ATLAS, 1202.5520

• the t-channel Z′ or scalar exchange models are excluded?

66

Same sign top pair production at LHC

CMS: σ(pp→tt( j))<17 pb at 95C.L. ATLAS: σ(pp→tt( j))<2 pb at 95C.L.

CMS, JHEP1108; ATLAS, 1202.5520

• the t-channel Z′ or scalar exchange models are excluded?

• the answer is NO.

• assume the large coupling to the down and

top quarks.

69

W’ model Cheung, Keung, Yuan, PLB682; Cheung, Yuan, PRD83

• free from the same sign top pair production.

d

d

W

• could be constrained by the Mtt

distribution.

• D0 data:

- support W′ model.

(15.2 4.0)%l

FBA D0, PRD84, 112005

Berger et al., PRL108, 072002

(SM: (2.1 0.1)%)l

FBA

70

Models with u-channel exchange

• color-sextet, color-triplet models etc.

Ligeti, Schmaltz, Tavares, JHEP1106; Shu, Tait, Wang, PRD81; Grinstein, Kagan, Trott, Zupan, PRL107

: SU(3)c Clebsch-Gordan coefficients connecting the color indices between scalar and quarks.

a

rT

• not constrained by the same sign top

pair.

• enhancement in the large tail.

Shu, Tait, Wang, PRD81

71

AFB and AC

ATLAS, 1203.4211

CMS

72

Model-independent approach Jung, Ko, Lee, Nam, PLB691; Jung, Ko, Lee, PLB701; PLB708; Zhang, Willenbrock, PRD83

• If new physics scale is high enough, the effective operator approach

where all heavy d.o.f. is integrated out is legitimate.

• useful approach even though AFB becomes close to the SM prediction.

73

1. Z′ dominant scenario

2. Higgs dominant scenario

3. Mixed scenario

cf. Babu, Frank, Rai, PRL107(2011)

cf. Jung, Murayama, Pierce, Wells, PRD81(2010) , ,Z h a

Z

2( ), ,

4

uaRut

X tu tu

g gY Y

Top-antitop pair production in chiral U(1)′ models

74

• decay into W+b in SM : Br(t→Wb)~100%.

• If the top quark decays to or , Br(t→Wb) might significantly

be changed. Z u h u

• requires Br(t →non-SM)<5% .

• choose either or . ' tZm m

h tm m

Top quark decay

75

• D0

• CMS

D0, 1105.2788

CMS, 1106.3052

( ) 2.90 0.59 pbpp tbq

( ) 83.6 29.8 3.3 pbpp tbq

In the SM,

2.1 1.5

0.7 1.7( ) 64.3 pbpp tbq

( ) 2.26 0.12 pbpp tbq

Single top quark production

76

• D0

• CMS

D0, 1105.2788

CMS, 1106.3052

( ) 2.90 0.59 pbpp tbq

( ) 83.6 29.8 3.3 pbpp tbq

In the SM,

2.1 1.5

0.7 1.7( ) 64.3 pbpp tbq

( ) 2.26 0.12 pbpp tbq

, ,Z h a

Single top quark production

⇒ no b quark or W boson in the final state

Z′ dominant case

77

= similar to Jung, Murayama, Pierce, Wells’ model (PRD81)

Favored region

78

Scalar Higgs (h) dominant case

= similar to Babu, Frank, Rai’s model (PRL107)

Favored region

Z′+h+a case

79

145 GeVZm

180 GeVhm

300 GeVam

1.1a

tuY

Favored region

• destructive interference between Z and Higgs bosons in the same signe top pair production.

• consistent with the CMS bound, but not with the ATLAS bound.

80

145 GeVZm

180 GeVhm

300 GeVam

0.01x

mixed case

Only Z′ case

1.0tuY

1.1a

tuY

145 GeVZm

0.029x

Invariant mass distribution

81

• In the SM,

LO,F NLO,F LO,B NLO,BSM LO NLOFB

LO NLO LO NLO

~ 8.7%.A

• In our calculation,

New LO NEW LO NEWFB

LO NEW LO NEW

( )~ 12%.

( )

KA

K

• Combining both contributions of NLO and New physics,

SM New

FB FB FB / ~18%.A A A K

AFB with SM NLO contribution

82

AFB versus σtt

145 GeVZm

180 GeV< 1 TeVhm

180 GeV< 1 TeVam

0.005< 0.025X

0.5<Y 1.5tu

0.5<Y 1.5a

tu

Z′+h+a case

83

AFB versus ACy

145 GeVZm

180 GeV< 1 TeVhm

180 GeV< 1 TeVam

0.005< 0.025X

0.5<Y 1.5tu

0.5<Y 1.5a

tu

Z′+h+a case

84

AFB versus σtt

145 GeVZm

180 GeV< 1 TeVhm

180 GeV< 1 TeVam

0.005< 0.025X

0.5<Y 1.5tu

0.5<Y 1.5a

tu

Excluded!

Z′+h+a case

85

AFB versus σtt

126 GeVhm

180 GeV< 1.5 TeVZm

180 GeV< 1 TeVam

0.005< 0.025X

0.1<Y 0.5tu

0.1<Y 1.5a

tu

Z′+h+a case

86

mZ' versus σtt

126 GeVhm

180 GeV< 1.5 TeVZm

180 GeV< 1 TeVam

0.005< 0.025X

0.1<Y 0.5tu

0.1<Y 1.5a

tu

Z′+h+a case

87

AFB versus σtt

125 GeVhm

180 GeV< 1 TeVHm

180 GeV< 1 TeVam

0< 0.025X

0<Y 0.5h

tu

0<Y 1.5a

tu

160 GeV< 300 GeVZm

0<Y 1.5H

tu

Z′+h+H+a case

88

AFB versus ACy

125 GeVhm

180 GeV< 1 TeVHm

180 GeV< 1 TeVam

0< 0.025X

0<Y 0.5h

tu

0<Y 1.5a

tu

160 GeV< 300 GeVZm

0<Y 1.5H

tu

Z′+h+H+a case

90

Tauonic B decays

(*)B D B

(b,c) coupling (b,u) coupling

b

q

q

cB

(*)D

W

b

q

q

cB

(*)D

h

b

u

BW

b

u

B h

• Both decays may be affected by the same new physics.

• SM

91

(*)B D

(*)B D

BABAR, 1205.5442 BABAR

SM

( )R D*( )R D

0.297 0.017

0.440 0.071 0.252 0.003

0.332 0.029

Fajfer,Kamenik,Nisandzic, Mescia

2.0 2.7

combined 3.4

92

*( ) and ( ) in 2HDM (type-II)R D R D

BABAR, 1205.5442

• Allowed regions:

tan / 0.44 0 fo ( ).02 r Hm R D

*tan / 0.75 0 for .04 ( )Hm R D

• Combination of and

excludes full parameter

space with 99.8% probability.

SM ( )R D *( )R D

b

q

q

ch

2

2

tan

H

bm mm

BABAR 2HDM

93

BR( )B

• Before 2012 summer

• After 2012 summer

Y.Horii, Tau 2012

94

BR( )B

Y.Horii, Tau 2012

95

Effective Hamiltonian

• Effective Hamiltonian

Charged Higgs

96

Wilson coefficients Type-II 2HDM

• only CR has sizable contribution.

97

2HDM

( )R D*( )R D

• Large CL with CR=0 could

explain data.

• Large CR is not capable of

achieving R(D(*)) without

sizable CL.

• Type-II 2HDM (or 2HDM III

with MFV) generate only CR.

→ could not explain R(D(*)).

Crivellin,Greub,Kokulu,1206.2634

98

2HDM with FCNCs From Minoru Tanaka’s slide at HPNP2013

99

B physics

• Charged Higgs contributes to B physics.

( ) ( ) ( )

( ) ( ) ( )

( ) ( ) ( )

( ) ( )

a a a

uu uc ut R

a a a

L L L cu cc ct R

a a a

tu tc tt R

Y Y Y u

u c t Y Y Y c h ia

Y Y Y t

( )

du dc dt R

L L L su sc st R

bu bc bt R

Y Y Y u

d s b Y Y Y c h

Y Y Y t

Neutral (pseudo)scalar

Charged Higgs sector

Top mass enhance Top AFB

strong relation *

CKM2( )u au

ij li ljY V Y

B (*)B D in one loopb s

100

Wilson coefficients

Flavor-independent

New terms in chiral U(1)΄ model

• diagonalization matrix gR

: the same as the type-II 2HDM.

: generate non-MFV interactions.

101

Constraints from B

SM

In our 2HDM

• The small tanβ is favored from the tree-level ρ parameter.

→ can be

( ) (0,0,1)ku

102

B In our 2HDM

• The BABAR discrepancies require large charged Higgs contribution

(*)B D and

• B→τν requires small (t,u) coupling,

- cannot achieve a large top AFB.

103

3HDM • 2 pairs of charged Higgs + 2 CP-odd pseudoscalars.

• parameter spaces are large → not difficult to find the allowed region

without fine-tuning.

• ex) degenerate case 1 2h h

m m

104

Conclusions

• We also constructed 2HDM and 3HDM, where gauged U(1) controls

FCNC.

- difficult to accommodate all with data within MFV models.

• chiral U(1)′ models provide non-MFV couplings.

• AFB and B→D(*)τν requires large new physics effects while B→τν

strongly suppress new physics effects.

• In 3HDM, it might be possible to achieve top AFB, BABAR discrepancies,

and B→τν.

• We proposed a new resoluton of the Higgs mediated FCNC problem in

2HDM with gauged U(1)H.

• easily realize “Natural Flavor Conservation” for proper U(1)H assignment.

2HDM and chiral U(1)′ models - Yonsei...

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