Multistep Single-Field Strong Phase Transitions from New Fermions - - PowerPoint PPT Presentation

Multistep Single-Field Strong Phase Transitions from New Fermions

Peisi Huang University of Nebraska-Lincoln @Searching for new physics- Leaving no stone unturned! University of Utah, Aug 9, 2019

Based on work with Andrei Angelescu, 1812.08293, PRD

What do we really know about the Higgs?

• We have discovered the Higgs boson and measured its

properties with precisions.

• However, we know very little about the Higgs potential.

V(Φ) Φ

vev, measured from GF

v ' 246 GeV

1

What do we really know about the Higgs?

• We have discovered the Higgs boson and measured its

properties with precisions.

• However, we know very little about the Higgs potential.

V(Φ) Φ

vev, measured from GF

v ' 246 GeV

2

Higgs mass measured at the LHC

mh ' 125 GeV

What do we really know about the Higgs?

• We have discovered the Higgs boson and measured its

properties with precisions.

• However, we know very little about the Higgs potential.

V(Φ) Φ

v ' 246 GeV

3

mh ' 125 GeV

• V = −µ2H†H + λh(H†H)2

Completely specify the Higgs potential in the SM, but NOT directly measured

• λh = M 2

h/(2v2) ' 0.13

µ2 = M 2

h/2 ' (88 GeV)2

What do we really know about the Higgs?

• We have discovered the Higgs boson and measured its

properties with precisions.

• However, we know very little about the Higgs potential.

V(Φ) Φ

v ' 246 GeV

4

mh ' 125 GeV

λ

κ 2 − 2 4 6 8 ] σ Significance [ 1 2 3 4 5 6 7 8 b b b b γ γ b b τ τ b b Combination

ATLAS Preliminary

• 1

= 14 TeV, 3000 fb s Simulation and Projections from Run 2 data Systematic uncertainties included

Self coupling, Limited sensitivity at HL-LHC

What do we want to know about the Higgs?

• The shape of the Higgs potential is closely related to the electroweak

phase transition.

V(Φ) Φ V(Φ) Φ

T=0 T >> 100 GeV Know nothing beyond v, and mh EW symmetry restored

?

5

Electroweak Phase Transitions

• First Order?
• In the SM, the EW symmetry is

broken by a smooth cross over.

• v (T) changes smoothly
• No energy barrier; no bubbles;
• no cosmological relics

6

V(Φ) Φ

T

Electroweak Phase Transitions

• For a first order phase transition,

7

λ

κ 2 − 2 4 6 8 ] σ Significance [ 1 2 3 4 5 6 7 8

b b b b γ γ b b τ τ b b Combination

ATLAS Preliminary

• 1

= 14 TeV, 3000 fb s Simulation and Projections from Run 2 data Systematic uncertainties included

' 5 3 < κλ < 3 (

PH, A. Joglekar, B. Li, and C. Wagner. 2015

Enough room for new physics

⇠

• ⇠
• V = µ2H†H λ(H†H)2 + f −2(H†H)3

Electroweak Phase Transitions

• First Order Phase Transition
• v is discontinuous
• Veff has a barrier, bubbles nucleated
• Possibly interesting cosmological

relics!

8

h h h h )

New physics to generate a barrier

V(Φ) Φ

Generating a barrier

9

SM + Scalar Singlet

Espinosa & Quiros, 1993; Benson, 1993; Choi & Volkas, 1993; McDonald, 1994; Vergara, 1996; Branco, Delepine, Emmanuel-Costa, & Gonzalez,1998; Ham, Jeong, & Oh, 2004; Ahriche, 2007; Espinosa & Quiros,2007; Profumo, Ramsey-Musolf, & Shaughnessy, 2007; Noble &Perelstein, 2007; Espinosa, Konstandin, No, & Quiros, 2008; Ashoorioon & Konstandin, 2009; Das, Fox, Kumar, & Weiner, 2009; Espinosa, Konstandin, & Riva, 2011; Chung & Long, 2011; Wainwright,Profumo, & Ramsey-Musolf, 2012; Barger, Chung, Long, & Wang, 2012; Huang, Shu, Zhang, 2012; Jiang, Bian, Huang, Shu, 2015; PH,Joglekar, Li, ,Wagner, 2015; Chen, Kozaczuk, & Lewis (2017)

SM + Scalar Doublet

Turok, Zadrozny 92, Davies, Froggatt, Jenkins, Moorhouse 94, Cline, Lemieux 97, Huber 06, Froome, Huber, Seniuch 06, Cline, Kainulainen, Trott 11, Dorsch, Huber, No 13, Dorsch, Huber, Mimasu, No 14, Basler, Krause, Muhlleitner, Wittbrodt, Wlotzka 16, Dorsch, Huber, Mimasu, No 17, Bernon, Bian, Jiang 17...

SM + Scalar Triplet

Patel, Ramsey-Musolf 12...

MSSM

Carena, Quiros, Wagner 96, Delepine, Gerard, Gonzalez Felipe, Weyers 96, Cline, Kainulainen 96, Laine, Rummukainen 98, Carena, Nardini, Quiros, Wagner 09, Cohen, Morrissey, Pierce 12, Curtin, Jaiswal, Meade 12, Carena, Nardini, Quiros, Wagner 13, Katz, Perelstein, Ramsey-Musolf, Winslow 14...

NMSSM

Pietroni 93, Davies, Froggatt, Moorhouse 95, Huber, Schmidt 01, Ham, Oh, Kim, Yoo, Son 04, Menon, Morrissey, Wagner 04, Funakubo, Tao, Yokoda 05, Huber, Konstandin, Prokopec, Schmidt 07, Chung, Long 10, Kozaczuk, Profumo, Stephenson Haskins, Wainwright 15...

Generating a barrier

• Scalars

V(Φ) Φ

(H†H) (

(H†H)2 (H†H)3

10

V (φh, φs, T) = m2

0 + a0T 2

2 φ2

h + λh

4 φ4

h + ahsφsφ2 h + λhs

2 φ2

sφ2 h + tsφs + m2 s

2 φ2

s + as

3 φ3

s + λs

4 φ4

s

Veff(H, T) = m2

0 + a0T 2

2 H2 + ✓λh 4 z 2y 2m2z 3v2 ◆ H4 + ✓8z2 4yzλh + 3yzλhs 6v2y ◆ H6.

Integrate out the singlet,

Generating a barrier

• Scalars
• Integrating out ,
• Thermal effect (high T expansion), negative cubic term
• Fermions
• Low T, scalars and fermions contribute equally

11

expansion)

(H†H)3

− T 2m2(φ) 2π2 K2

• m(φ)/T
• + O
• T 2m(φ)2e−2m(φ)/T

Consider the possibility of generating a barrier through fermions in this talk – leaving no stones unturned!

Outline

• Consider a Vector-Like Lepton (VLL) model.
• A non-trivial thermal history of the universe.
• Signatures
• Gravitational Wave signatures
• Collider signatures

12

A Minimal Vector-Like Lepton (VLL) Model

• Fermion models for strong first order phase transitions?
• Strong couplings to the Higgs!
• To avoid large mixing between the VLLs and SM leptons, and large

contributions to the T parameter, we add

LL,R = ✓ N E ◆

L,R

∼ (1, 2)1/2, N 0

L,R ∼ (1, 1)0,

E0

L,R ∼ (1, 1)1

• The most general Lagrangian is,

× × −LV LL = yNRLL ˜ HN 0

R + yNLN L ˜

H†LR + yERLLHE0

R + yELE LH†LR

+ mLLLLR + mNN

LN 0 R + mEE LE0 R + h.c. ,

13

A Minimal Vector-Like Lepton (VLL) Model

• 2 neutral and 2 charged VLLs
• Ranges of the parameters considered,

× × −LV LL = yNRLL ˜ HN 0

R + yNLN L ˜

H†LR + yERLLHE0

R + yELE LH†LR

+ mLLLLR + mNN

LN 0 R + mEE LE0 R + h.c. ,

mL, mN, mE ∈ [500, 1500] GeV, yNL,R, yEL,R ∈ [2, √ 4π].

• Constraints:
• S & T parameters
• Diphoton signal strength,
• Masses of the lighter states,

0.71 < µγγ < 1.29 eigenstates, m >

ATLAS, 1802.04146

es, mE1 > 100 GeV and mN1 > 90 GeV

LEP2, Phys Rept 427(2006)257-454

14

Thermal Evolution of the Effective Potential

• For each surviving point, calculate the phase transition strength, ξ = φc/Tc

V (φ, T) = V SM

tree (φ) + V SM 1−loop(φ, T) + V V LL 1−loop(φ, T) + VDaisy(φ, T)

(

• Benchmark A,

yNL ' 3.40, yNR ' 3.49, yEL ' 3.34, yER ' 3.46, mL ' 1.06 TeV, mN ' 0.94 TeV, mE ' 1.34 TeV. µγγ = 1.28, ∆χ2(S, T) = 1.33, mN1 = 400 GeV, mE1 = 592 GeV.

+ + + + · · ·

15

Thermal Evolution of the Effective Potential

Cross over Early universe, symmetric EWSB

16

Thermal Evolution of the Effective Potential

• The broken minimum becomes less and less deep
• A potential barrier starts developing between the

symmetric phase and the broken phase

• At Tc2 , a strong first order phase transition
• The universe tunnels back to the symmetric phase

EW symmetry restored

17

Thermal Evolution of the Effective Potential

EWSB again through a strongly first order phase transition, at Tc1

18

Thermal Evolution of the Effective Potential

Responsible for the BAU

19

Outline

• Consider a Vector-Like Lepton (VLL) model.
• A non-trivial thermal history of the universe.
• Signatures
• Gravitational wave signatures
• Collider signatures

× × −LV LL = yNRLL ˜ HN 0

R + yNLN L ˜

H†LR + yERLLHE0

R + yELE LH†LR

+ mLLLLR + mNN

LN 0 R + mEE LE0 R + h.c. ,

20

Signatures – Gravitational Waves

• When the bubbles collider, some of their energy is transferred to

gravitational radiation, and persists today as stochastic GW background.

• Multi-peak gravitational waves from a single scalar field!
• GW spectrum is (mostly) determined by two parameters,

− −

α = latent heat radiation energy

Larger 𝛽, stronger signal Larger 𝛾, weaker signal, higher frequencies

• Typically, for the later phase transition,

α ∼ 0.01 − 0.1, β/HPT ∼ 103 − 104.

g α2 < α1 and (β/HPT)2 > (β/HPT)1. are listed in Table. 2. We show in Fig.

• For the earlier one,

21

β = PT rate

Signatures – Gravitational Waves

• Peak frequency beyond Lisa ( f~ 0.01 -1 Hz is typical for VLL models)
• DECIGO, BBO, and AION are sensitive to the later phase transition
• The earlier one is too weak.

22

GW comparison with the singlet models

23

feeds into grav. wave calc.

L = Lsm + 1 2

• ∂µS
• ∂µS
• tsS m2

s

2 S2 as 3 S3 λs 4 S4 λhsΦ†ΦS2 2ahsΦ†ΦS .

= , ()/ > 0 = “” , ()/ > 1.3 = 1, PH, A. Long, L. Wang, 2017

Fermions

α ⇠ 10−3 10−1, β/HPT ⇠ 102 106

α ⇠ 0.01 0.1, β/HPT ⇠ 103 104

Weaker signal at higher frequencies

GW comparison with the singlet models

550 600 650 700 750 800 0.01 0.02 0.05 0.10 0.20 0.50 1.00

f [Gev] α

24

550 600 650 700 750 800 850 1 100 104 106

f [Gev] β/HPT

⇠

• ⇠
• V = µ2H†H λ(H†H)2 + f −2(H†H)3
• A. Angelescu, PH, arxiv:19xx.xxxx

For the fermion benchmark, f~ 550 GeV as calculated from the full theory

− α ∼ 0.07, β/HP T ∼ 1800

Preliminary

GW comparison with the singlet models

25

= , ()/ > 0 = “” , ()/ > 1.3 = 1,

550 600 650 700 750 800 0.01 0.02 0.05 0.10 0.20 0.50 1.00

f [Gev] α

550 600 650 700 750 800 850 1 100 104 106

f [Gev] β/HPT PH, A. Long, L. Wang, 2017

• A. Angelescu, PH, arxiv:19xx.xxxx

feeds into grav. wave calc.

Preliminary

Signatures – Colliders, Direct Production

• N1 can not be dark matter candidate – some mixing required.

Lmix = y1 LLH⌧R + y2 L

3 LHE0 R + h.c. ,

• From W𝜐𝜉 and Z𝜐𝜐 measurements, take
• The SM fermion + VLL production is suppressed by the mixing
• The dominant production mode is the pair production of VLLs, the

typical production cross section is around 0.1 to 0.4 fb.

• Direct searches at the LHC very challenging.

se y1 = y2 = 0.05. ions from the SM

26

Signatures – Colliders, Indirect Searches

• At least 15%

enhancement for the diphoton signal.

• Wil be fully tested at

the HL-LHC.

27

Conclusion

• VLLs can give rise to a non-trivial thermal history of the universe.

× × −LV LL = yNRLL ˜ HN 0

R + yNLN L ˜

H†LR + yERLLHE0

R + yELE LH†LR

+ mLLLLR + mNN

LN 0 R + mEE LE0 R + h.c. ,

28

Conclusion

• VLLs can give rise to a non-trivial thermal history of the universe.
• Multi-step phase transitions with a single scalar field!
• The later of the phase transition can be probed by BBO and DECIGO.

29

Conclusion

• VLLs can give rise to a non-trivial thermal history of the universe.
• Multi-step phase transitions with a single scalar field!
• The later of the phase transition can be probed by BBO and DECIGO.
• At least 15% enhancement in the diphoton signal is expected, so the

model will be fully tested by the HL-LHC.

30