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 Junwu Huang Perimeter Institute Oct, 2019 @ GGI 1904.00020 , 1907.10624 , 1908.00019 Anson Hook, Junwu Huang, Davide Racco

Hierarchy problem • EW hierarchy problem & CC problem • Symmetry + Naturalness • Landscape/Multiverse + Anthropics (Credit: Giovanni Villadoro)

Multiverse • “…knowing that it could be out there is itself very important information…” (Nima or Savas) • Weinberg CC One step further: • String Axiverse see a new minimum! 0905.4720 • Split Supersymmetry hep-ph/0406088, hep-ph/0409232,1210.0555 • How can we directly look for a minimum? • Local bubbles • High scale higgs minimum

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 Anson Hook, JH , arXiv:1904.00020 • Go back into the past: High scale Higgs minimum

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) V ( h ) • Higgs instability 1505.04825 λ h < 0@ v λ =0 ∼ 10 11 GeV v ew v uv • Higgs quartic h v λ =0 • The EW minimum v EW is meta-stable T = 0 H ≲ 6 × 10 13 GeV • 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?

Higgs instability (Implications) V ( h ) • Higgs instability 1505.04825 λ h < 0@ v λ =0 ∼ 10 11 GeV v ew v uv • Higgs quartic h v λ =0 • The EW minimum v EW is meta-stable T = 0 H ≲ 6 × 10 13 GeV • 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? 1711.03988 • Can we be in a high scale Higgs minimum all along?

A new Higgstory V ( h ) • During inflation • Higgs fluctuate over and roll to the UV minimum. v λ =0 v ew v uv h v λ =0 • Stay there the whole time when v UV > H T = 0 H • Require : Stringy/GUT contribution stabilize runaway direction V ( h ) • After inflation: T = T max • Thermal contribution lift the UV minimum v ew v uv h v λ =0 • The Higgs rolls back and decays through scattering with background SM radiation T = 0 • Require : Reheat to temperatures T max > v UV

A new Higgstory V ( h ) • During inflation • Higgs fluctuate over and roll to the UV minimum. v λ =0 v ew v uv h v λ =0 • Stay there the whole time when v UV > H T = 0 H • Require : Stringy/GUT contribution stabilize runaway direction V ( h ) • After inflation: T = T max • Thermal contribution lift the UV minimum v ew v uv h v λ =0 • The Higgs rolls back and decays through scattering with background SM radiation T = 0 • Require : Reheat to temperatures T max > v UV

Summary: parameter space 10 15 10 14 Bound on r 10 13 No instability at + 2 � in m t In all of the No instability at 0 � in m t 10 12 white region, our history 10 11 would apply. 10 10 V � + V h < 0 T RH < v UV 10 9 10 8 10 7 10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16

Cosmological collider of SM fermions

Primordial perturbations (Brief) ζ (x 1 ) • Primordial perturbation ζ (x) ζ (x 3 ) …their correlations ⟨ ζ ( x 1 ) ζ ( x 2 )… ζ ( x n ) ⟩ encodes information of inflation ζ (x 2 ) • Correlation functions (Fourier) k 2 k 1 ⟨ ζ ( x 1 ) ζ ( x 2 )… ζ ( x n ) ⟩ → ⟨ ζ ( k 1 ) ζ ( k 2 )… ζ ( k n ) ⟩ k 3

⃗ ⃗ ⃗ ⃗ Power spectrum (leading effect) • Power spectrum (leading effect): τ = 0 ⟨ δϕ ( k 1 ) δϕ ( k 2 ) ⟩ ∼ H 2 δ ( k 2 k 2 ) k 1 k 1 + k 3 1 ~ k 1 + ~ k 2 = 0 • Density correlation function: ⟨ ζ ( k 1 ) ζ ( k 2 ) ⟩ = (2 π ) 3 2 π 2 P ζ δ ( k 2 ) { k 1 + k 3 1 ⟨ ζ (0) ζ ( x ) ⟩ ∼ H 2 log | x | ζ (x 1 ) ζ (x 2 )

Non-Gaussianity (Brief) • Non-gaussianity: τ = 0 k 2 k 1 k 3 ⌧ k 1 0 k 2 • Cosmological collider ( δφ ) 3 0911.3380, 1503.08043 • Cosmological collider physics concerns the case where there are intermediate massive particles • Massive particle redshifts differently • and lead to oscillating shapes in the k 3 < k 2 ∼ k 1 squeezed limit ( )

Cosmological collider (Brief) • Non-gaussianity: τ = 0 k 2 k 1 k 3 ⌧ k 1 0 k 2 • Cosmological collider ( δφ ) 3 0911.3380, 1503.08043 • Cosmological collider physics τ = 0 concerns the case where there are k 2 intermediate massive particles k 1 • Massive particle redshifts differently k 3 ⌧ k 1 0 k 2 m/H • and lead to oscillating shapes in the k 3 < k 2 ∼ k 1 squeezed limit ( ) ( δφ ) 3

Cosmological collider (Brief) Muon/Galaxy Tracker/CMB Collision/Inflation Calorimeter/21cm (Credit: Zhong-Zhi Xianyu) 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 Anson Hook, JH , Davide Racco, arXiv:1908.00019 • How to use SM fermions? τ = 0 δφ δφ k 2 k 1 • Couple them to inflaton (shift symmetric): τ 1 τ 2 f δφ k 3 ⌧ k 1 0 k 2 f f 1805.02656 τ 3

τ = 0 A fermion story δφ δφ k 2 k 1 τ 1 τ 2 f δφ k 3 ⌧ k 1 0 k 2 • Fermion dispersion relation (small Hubble) f f • Rolling inflaton ( ) breaks Lorentz Symmetry τ 3 • Fermion production ( ) H ≪ m ≪ λ ( k 3 ∼ ω ( τ 3 ) ∼ m ) ( ω ∼ m , k ∼ ± λ ) • Fermion mode: • Production rate: • Effective density: • Fermion redshift • Fermion annihilation

τ = 0 A fermion story δφ δφ k 2 k 1 τ 1 τ 2 f δφ k 3 ⌧ k 1 0 k 2 f f • Fermion dispersion relation τ 3 • Fermion production ( ) H ≪ m ≪ λ Non-adiabatic particle ( ω ∼ m , k ∼ ± λ ) • Fermion mode: production • Production rate: • Effective density: • Fermion redshift • Fermion annihilation

A fermion story • Fermion dispersion relation: τ = 0 • Fermion production δφ δφ k 2 k 1 τ 1 τ 2 f • Fermion redshift: ( k 3 ∼ ω ( τ 3 ) ∼ m ) δφ k 3 ⌧ k 1 0 k 2 f ( ω ∼ m , k ∼ λ ) ( ω ∼ λ , k ∼ 0 ) f • From to sets oscillation frequency ω ∼ λ τ 3 • • Fermion annihilation ( ω ∼ λ , k ∼ 0 ) • Fermions can only pair annihilate ( k 2 ∼ k 1 ∼ ω ( τ 1 ) ∼ λ ) k 3 ∼ m k 1 λ

Results & implications

Signal strength • Signal from a fermion loop: • Shape: • Amplitude: 10 2 10 1 10 0 10 - 1 10 - 2 10 - 1 10 0 10 1

Signal strength 0.1 0.2 0.3 0.4 0.5 10 7 10 6 Take home: 10 5 1. SM fermions scan Hubble 2. Multiple SM fermions can be observed together 10 4 10 3 10 2 0 10 20 30 40

Distinguishing the signal • How to distinguish the signal: • Amplitude (f NL ) and frequency -> Mass (m/H) & Coupling ( λ /H) 0.1 0.2 0.3 0.4 0.5 10 7 • Two/multiple fermions: 10 6 • Ratio of fermion masses: 10 5 • Implications: 10 4 10 3 • A new minimum! 10 2 0 10 20 30 40 • New probe of GUT, string theories… • No two Higgs doublet, no new coloured states…

Implications • How to distinguish the signal: • Amplitude (f NL ) and frequency -> Mass (m/H) & Coupling ( λ /H) • Two/multiple fermions: • Ratio of fermion masses: We can look for the • Implications: landscape, directly! • A new minimum! • UV: New probe of GUT, string theories… • IR: No two Higgs doublets, no many new coloured states…

Low(er) risk & low(er) reward Anson Hook, JH , Davide Racco arXiv:1908.00019

Parameter space II 10 15 • Green: Lighter Bound on r 10 14 SM fermions. 10 13 m u m i n i m • Above Blue line: l a 10 12 c i m a n y a d Top quark m y i l 10 11 n n i o m o w � t � h = 0 � h = 0 10 10 � � T RH < v UV How does the 10 9 SM fermion 10 8 density affect + 2 � m t 0 � m t 10 7 Higgs potential? 10 6 10 8 10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16

Dynamical Higgs minimum • Fermions produced (effective density): ? f h 2 ≫ H 2 h 2 m f n f ∼ y 2 f λ 2 Top quark • Fermions impact the Higgs potential density affect Higgs potential! • Correction to mass (small mass limit):

Dynamical Higgs minimum • Fermions produced (effective density): ? f h 2 ≫ H 2 h 2 m f n f ∼ y 2 f λ 2 • Fermions impact the Higgs potential p 12 p 12 − → − → k 1 k 1 k 1 k 1 ˙ ˙ β β α α + − → − → − → − → a a b b α α β ˙ ˙ β p 21 p 21 ← − ← − • Correction to mass (small mass limit): Especially the top quark

Dynamical Higgs minimum V ( h ) • Dynamical equilibrium: λ t = 0 1. Fermion production v ew 2. Higgs roll to the minimum v h 3. Fermions become heavy λ t ̸ = 0 4. Particle production shuts off • The resulting Higgs potential:

Dynamical Higgs minimum • The resulting Higgs potential: • The dynamical Higgs minimum: V ( h ) λ t = 0 v ew v h H = ( 1/2 π H ) m t λ t λ t ̸ = 0