Searches for new vacua II: A new Higgstory at the cosmological - - PowerPoint PPT Presentation

Searches for new vacua II: A new Higgstory at the cosmological collider

1904.00020, 1907.10624, 1908.00019 Anson Hook, Junwu Huang, Davide Racco

Junwu Huang

Perimeter Institute Oct, 2019 @ GGI

Hierarchy problem

(Credit: Giovanni Villadoro)

• EW hierarchy problem &

CC problem

• Symmetry + Naturalness
• Landscape/Multiverse +

Anthropics

Multiverse

• “…knowing that it could be out there is itself very

important information…” (Nima or Savas)

• Weinberg CC
• String Axiverse
• Split Supersymmetry
• How can we directly look for a minimum?
• Local bubbles
• High scale higgs minimum

One step further: see a new minimum!

0905.4720 hep-ph/0406088, hep-ph/0409232,1210.0555

Multiverse

• “…knowing that it could be out there is itself very

important information” (Nima or Savas)

• Weinberg CC
• String Axiverse
• Split Supersymmetry
• How can we directly look for a minimum?
• Go far away: Local bubbles
• Go back into the past: High scale Higgs minimum

Anson Hook, JH, arXiv:1904.00020

Outline

• The higgstory
• The tale of SM fermions
• Result and remarks
• A lower risk lower reward signal

Anson Hook, JH, Davide Racco arXiv:1908.00019

A new Higgstory

Higgs instability (Brief)

• Higgs instability
• Higgs quartic
• The EW minimum vEW is meta-stable
• During inflation (

), Higgs could leave EW minimum.

• What does Higgs instability + High scale inflation imply?
• New physics at low energy scales?
• New coupling of Higgs to Hubble/Inflaton?
• Can we be in a high scale Higgs minimum all along?

λh < 0@vλ=0 ∼ 1011 GeV H ≲ 6 × 1013 GeV

h V (h) vew vλ=0 vuv T = 0

1505.04825

Higgs instability (Implications)

• Higgs instability
• Higgs quartic
• The EW minimum vEW is meta-stable
• During inflation (

), Higgs could leave EW minimum.

• What does Higgs instability + High scale inflation imply?
• New physics at low energy scales?
• New coupling of Higgs to Hubble/Inflaton?
• Can we be in a high scale Higgs minimum all along?

λh < 0@vλ=0 ∼ 1011 GeV H ≲ 6 × 1013 GeV

h V (h) vew vλ=0 vuv T = 0

1505.04825 1711.03988

A new Higgstory

• During inflation
• Higgs fluctuate over

and roll to the UV minimum.

• Stay there the whole time when
• Require: Stringy/GUT contribution stabilize runaway

direction

• After inflation:
• Thermal contribution lift the UV minimum
• The Higgs rolls back and decays through scattering

with background SM radiation

• Require: Reheat to temperatures

vλ=0 vUV > H Tmax > vUV

h V (h) vew vλ=0 vuv T = 0 T = Tmax

H

h V (h) vew vλ=0 vuv T = 0

A new Higgstory

• During inflation
• Higgs fluctuate over

and roll to the UV minimum.

• Stay there the whole time when
• Require: Stringy/GUT contribution stabilize runaway

direction

• After inflation:
• Thermal contribution lift the UV minimum
• The Higgs rolls back and decays through scattering

with background SM radiation

• Require: Reheat to temperatures

vλ=0 vUV > H Tmax > vUV

h V (h) vew vλ=0 vuv T = 0 T = Tmax

H

h V (h) vew vλ=0 vuv T = 0

Summary: parameter space

In all of the white region,

• ur history

would apply.

109 1010 1011 1012 1013 1014 1015 1016 107 108 109 1010 1011 1012 1013 1014 1015

Bound on r No instability at 0 in mt No instability at +2 in mt TRH<vUV V+Vh<0

Cosmological collider

• f

SM fermions

Primordial perturbations (Brief)

• Primordial perturbation ζ(x)
• Correlation functions (Fourier)

ζ(x1) ζ(x2) ζ(x3) k1 k2 k3

…their correlations encodes information of inflation

⟨ζ(x1)ζ(x2)…ζ(xn)⟩

⟨ζ(x1)ζ(x2)…ζ(xn)⟩ → ⟨ζ(k1)ζ(k2)…ζ(kn)⟩

Power spectrum (leading effect)

• Power spectrum (leading effect):
• Density correlation function:

ζ(x1) ζ(x2)

⟨ζ(0)ζ(x)⟩ ∼ H2 log|x|

⟨ζ(k1)ζ(k2)⟩ = (2π)3 2π2Pζ k3

1

δ ( ⃗ k 1 + ⃗ k 2)

{

k1 k2 τ = 0

~ k1 + ~ k2 = 0

⟨δϕ(k1)δϕ(k2)⟩ ∼ H2 k3

1

δ ( ⃗ k 1 + ⃗ k 2)

Non-Gaussianity (Brief)

• Non-gaussianity:
• Cosmological collider
• Cosmological collider physics

concerns the case where there are intermediate massive particles

• Massive particle redshifts differently
• and lead to oscillating shapes in the

squeezed limit ( )

k3 < k2 ∼ k1

k1 k2 k3 ⌧ k10k2 τ = 0

(δφ)3

0911.3380, 1503.08043

Cosmological collider (Brief)

• Non-gaussianity:
• Cosmological collider
• Cosmological collider physics

concerns the case where there are intermediate massive particles

• Massive particle redshifts differently
• and lead to oscillating shapes in the

squeezed limit ( )

k3 < k2 ∼ k1

0911.3380, 1503.08043

k1 k2 k3 ⌧ k10k2 τ = 0

(δφ)3 k1 k2 k3 ⌧ k10k2 m/H τ = 0

(δφ)3

Cosmological collider (Brief)

(Credit: Zhong-Zhi Xianyu)

Muon/Galaxy Tracker/CMB Collision/Inflation Calorimeter/21cm

CMS detector

Using SM Fermions

• Why fermions?
• SM fermion masses scan many order of magnitude
• Fermions have no hierarchy problem
• Fermions enhance EW symmetry breaking
• How to use SM fermions?
• Couple them to inflaton (shift symmetric):

k1 k2 k3 ⌧ k10k2 f δφ f δφ f δφ τ = 0

τ1 τ2 τ3

1805.02656

Anson Hook, JH, Davide Racco, arXiv:1908.00019

A fermion story

• Fermion dispersion relation (small Hubble)
• Rolling inflaton ( ) breaks Lorentz Symmetry
• Fermion production ( )
• Fermion mode:
• Production rate:
• Effective density:
• Fermion redshift
• Fermion annihilation

(ω ∼ m, k ∼ ± λ)

k1 k2 k3 ⌧ k10k2 f δφ f δφ f δφ τ = 0

τ1 τ2 τ3

(k3 ∼ ω(τ3) ∼ m)

H ≪ m ≪ λ

A fermion story

• Fermion dispersion relation
• Fermion production ( )
• Fermion mode:
• Production rate:
• Effective density:
• Fermion redshift
• Fermion annihilation

(ω ∼ m, k ∼ ± λ)

k1 k2 k3 ⌧ k10k2 f δφ f δφ f δφ τ = 0

τ1 τ2 τ3

Non-adiabatic particle production

H ≪ m ≪ λ

A fermion story

• Fermion dispersion relation:
• Fermion production
• Fermion redshift:
• From

to

• sets oscillation frequency
• Fermion annihilation
• Fermions

can only pair annihilate

(ω ∼ m, k ∼ λ) (ω ∼ λ, k ∼ 0) ω ∼ λ (ω ∼ λ, k ∼ 0)

k1 k2 k3 ⌧ k10k2 f δφ f δφ f δφ τ = 0

τ1 τ2 τ3

(k2 ∼ k1 ∼ ω(τ1) ∼ λ) (k3 ∼ ω(τ3) ∼ m) k3 k1 ∼ m λ

Results & implications

Signal strength

• Signal from a fermion loop:
• Shape:
• Amplitude:

10-1 100 101 10-2 10-1 100 101 102

Signal strength

10 20 30 40 102 103 104 105 106 107 0.1 0.2 0.3 0.4 0.5

Take home:

• 1. SM fermions scan Hubble
• 2. Multiple SM fermions can

be observed together

Distinguishing the signal

• How to distinguish the signal:
• Amplitude (fNL) and frequency -> Mass (m/H) & Coupling

(λ/H)

• Two/multiple fermions:
• Ratio of fermion masses:
• Implications:
• A new minimum!
• New probe of GUT, string theories…
• No two Higgs doublet, no new coloured states…

10 20 30 40 102 103 104 105 106 107 0.1 0.2 0.3 0.4 0.5

Implications

• How to distinguish the signal:
• Amplitude (fNL) and frequency -> Mass (m/H) & Coupling

(λ/H)

• Two/multiple fermions:
• Ratio of fermion masses:
• Implications:
• A new minimum!
• UV: New probe of GUT, string theories…
• IR: No two Higgs doublets, no many new coloured states…

We can look for the landscape, directly!

Low(er) risk & low(er) reward

Anson Hook, JH, Davide Racco arXiv:1908.00019

• Green: Lighter

SM fermions.

• Above Blue line:

Top quark

Parameter space II

How does the SM fermion density affect Higgs potential?

108 109 1010 1011 1012 1013 1014 1015 1016 106 107 108 109 1010 1011 1012 1013 1014 1015

Bound on r TRH<vUV

• n

l y d y n a m i c a l m i n i m u m

• t

w

• m

i n i m a 0 mt +2 mt h=0 h=0

• Fermions produced (effective density):
• Fermions impact the Higgs potential
• Correction to mass (small mass limit):

Dynamical Higgs minimum

mfnf ∼ y2

f λ2 f h2 ≫ H2h2

?

Top quark density affect Higgs potential!

• Fermions produced (effective density):
• Fermions impact the Higgs potential
• Correction to mass (small mass limit):

Dynamical Higgs minimum

k1

− →

p12

− →

p21

← −

k1

− →

a b α β ˙ β ˙ α

+

k1

− →

k1

− →

p12

− →

p21

← −

a b ˙ β ˙ α α β

Especially the top quark

?

mfnf ∼ y2

f λ2 f h2 ≫ H2h2

h V (h) vew v λt = 0 λt ̸= 0

Dynamical Higgs minimum

• Dynamical equilibrium:

1. Fermion production 2. Higgs roll to the minimum 3. Fermions become heavy 4. Particle production shuts off

• The resulting Higgs potential:

h V (h) vew v λt = 0 λt ̸= 0

• The resulting Higgs potential:
• The dynamical Higgs minimum:

Dynamical Higgs minimum

mt H = ( λt πH )

1/2

One parameter signal

• The signal shape:
• The signal amplitude:

20 25 30 35 40 100 101 102 0.2 0.3 0.4

k1 k2 k3 ⌧ k10k2 t δφ t δφ t δφ τ = 0

τ1 τ2 τ3

One parameter signal

108 109 1010 1011 1012 1013 1014 1015 1016 106 107 108 109 1010 1011 1012 1013 1014 1015

Bound on r TRH<vUV

• n

l y d y n a m i c a l m i n i m u m

• t

w

• m

i n i m a 0 mt +2 mt h=0 h=0

• n
• n

p e r t . e x p . 0 mt +2 mt

• Blue + Green: Dynamical minimum with Top quark signal
• Green: Lighter SM fermions signal from a true minimum

Conclusion

• Higgs can be in a distinct minimum during inflation
• Cosmological collider physics offers a way to tell
• The minimum can be a physical one, and we can

measure signals from light SM quarks

• The minimum can be generated dynamically, and

the top quark can be looked for

Does one new minimum hint multiverse? Would a few of them convince you?

Sempre caro mi fu quest'ermo colle, e questa siepe, che da tanta parte dell'ultimo orizzonte il guardo esclude. Ma sedendo e mirando, interminati spazi di là da quella...

• - Giacomo Leopardi