Supersymmetric Dark Matter Minseok Cho KAIST December 07, 2019 1 - - PowerPoint PPT Presentation

Supersymmetric Dark Matter

Minseok Cho KAIST December 07, 2019

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SUPERSYMMETRIC DARK MATTER

Table of Contents

• 1. Dark Matter
• 2. Relic Abundance of WIMPs
• 3. Minimal Supersymmetric Standard Model (MSSM)
• 4. Detection of WIMPs

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Evidence for Existence of Dark Matter

Fritz Zwicky

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Coma Cluster

Evidence for Existence of Dark Matter

Rotation Curve of NGC 6503

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Vera Rubin

Nonbaryonic Dark Matter

Density parameter :

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• pen universe, expand forever

flat universe close universe, halt expanding and recollapse

𝜍 =

Nonbaryonic Dark Matter

To explain abundance of Helium, Deuterium, and Lithium

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• Measurements suggest
• Bulk of dark matter is nonbaryonic
• )

(WMAP, in LCDM model)

Candidates of Dark Matter

• 1. Massive Compact Halo Objects (MACHOs)
• Neutron stars, brown dwarfs, black holes, etc.
• EROS-2 researches gravitational microlensing effects. But not observed.
• 2. Hot dark matter
• Neutrino
• N-body simulation was inconsistent.
• 3. Weakly Interacting Massive Particles (WIMPs)
• Supersymmetry, extra dimension, little Higgs theory, etc.

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Relic Abundance of WIMPs

Relic Abundance : how many particles remain from the early universe

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𝑜

=

𝑕 2𝜌 𝑔 𝑞 𝑒𝑞 𝑜

∝ 𝑈

For 𝑈 ≫ 𝑛, 𝑜

∝ 𝑕 𝑛𝑈 2𝜌

⁄

⁄ exp − 𝑛 𝑈

⁄ For 𝑈 ≪ 𝑛,

But, the universe is not completely in thermal equilibrium

Relic Abundance of WIMPs

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𝜓𝜓̅ ↔ 𝑦𝑦̅ Γ = 𝑜 𝜏𝑤 For 𝑈 ≫ 𝑛, When Γ = 𝐼, 𝜓 stops to annihilate (freeze out) 𝜓 is abundant and annihilation is active Annihilation rate :

Relic Abundance of WIMPs

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𝑜 𝑡 ⁄

= 𝑜 𝑡

⁄

= Γ

𝜏𝑤 𝑡 ⁄ = 𝐼 𝜏𝑤 𝑡 ⁄ In freeze-out condition

Then

≃ 100 𝑛𝑛𝑕∗

⁄

𝜏𝑤

• Ωℎ = 𝑛𝑜 𝜍

⁄ ≃ (3 × 10 cms/ 𝜏𝑤 )

Relic Abundance of WIMPs

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𝑒𝑜 𝑒𝑢 + 3𝐼𝑜 = − 𝜏𝑤 𝑜

− 𝑜

By the Boltzmann equation, Larger cross section → smaller relic abundnace Cross section of WIMPs 𝜏𝑤 ∼ 10 cm s

Minimal Supersymmetric Standard Model (MSSM)

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MSSM = Standard model + Higgs doublet + SUSY partners MSSM follows the gauge symmetry SU(3) × SU(2) × U(1) R-parity : 𝑆 = −1 𝑆 = 1 for ordinary SM particles 𝑆 = −1 for superpartners

Minimal Supersymmetric Standard Model (MSSM)

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Annihilation Cross-section

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Detection of WIMPs

• 1. Direct detection
• Very low cross section
• Tiny deposited energy

20 - 400 GeV, 270 km/s WIMPs & 1 – 200 GeV nucleus ⇒ deposit 1 - 100 keV energy, 10-4 - 1 event per day per kilogram of matter

• Background cosmic ray

keV - MeV cosmic ray in 100 events per day per kilogram

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Detection of WIMPs

• 2. Observe energetic neutrinos from the Sun / Earth

Occasionally scattered

↓

Smaller velocity than the escape velocity

↓

Trapped in the sun

↓

Additional scattering, settles to the core

↓

Energetic neutrino from annihilation of WIMPs in the core

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