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SupersymmetricDark Matter
Minseok Cho
KAIST
December 07, 2019
1SUPERSYMMETRIC DARK MATTER
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Table of Contents1. Dark Matter
2. Relic Abundance of WIMPs
3. Minimal Supersymmetric Standard Model (MSSM)
4. Detection of WIMPs
SUPERSYMMETRIC DARK MATTER 2
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Evidence for Existence of Dark MatterFritz Zwicky
SUPERSYMMETRIC DARK MATTER 3MINSEOK CHO
Coma Cluster
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Evidence for Existence of Dark MatterRotation Curve of NGC 6503
SUPERSYMMETRIC DARK MATTER 4MINSEOK CHO
Vera Rubin
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Nonbaryonic Dark MatterDensity parameter :
SUPERSYMMETRIC DARK MATTER 5MINSEOK CHO
open universe, expand forever
flat universe
close universe, halt expanding and recollapse
𝜌 =
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Nonbaryonic Dark MatterTo explain abundance of Helium, Deuterium, and Lithium
SUPERSYMMETRIC DARK MATTER 6MINSEOK CHO
Measurements suggest
Bulk of dark matter is nonbaryonic
)
(WMAP, in LCDM model)
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Candidates of Dark Matter1. 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.
SUPERSYMMETRIC DARK MATTER 7MINSEOK CHO
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Relic Abundance of WIMPsRelic Abundance : how many particles remain from the early universe
SUPERSYMMETRIC DARK MATTER 8MINSEOK CHO
𝑛 =𝑔
2𝜋𝑓 𝑝 𝑑 𝑝
𝑛 ∝ 𝑇For 𝑇 ≫ 𝑚 ,
𝑛 ∝ 𝑔 𝑚 𝑇 2𝜋⁄⁄
exp − 𝑚 𝑇⁄For 𝑇 ≪ 𝑚 ,
But, the universe is not completely in thermal equilibrium
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Relic Abundance of WIMPs
SUPERSYMMETRIC DARK MATTER 9MINSEOK CHO
𝜒�̅� ↔ 𝑥�̅�
Γ = 𝑛 𝜎𝑣
For 𝑇 ≫ 𝑚 ,
When Γ = 𝐻, 𝜒 stops to annihilate (freeze out)
𝜒 is abundant and annihilation is active
Annihilation rate :
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Relic Abundance of WIMPs
SUPERSYMMETRIC DARK MATTER 10MINSEOK CHO
𝑛 𝑠⁄ = 𝑛 𝑠⁄ = Γ 𝜎𝑣 𝑠⁄ = 𝐻 𝜎𝑣 𝑠⁄
In freeze-out condition
Then
≃ 100 𝑚 𝑚 𝑔∗⁄
𝜎𝑣
Ω ℎ = 𝑚 𝑛 𝜌⁄ ≃ (3 × 10 cm s / 𝜎𝑣 )
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Relic Abundance of WIMPs
SUPERSYMMETRIC DARK MATTER 11MINSEOK CHO
𝑑𝑛
𝑑𝑡+ 3𝐻𝑛 = − 𝜎𝑣 𝑛 − 𝑛
By the Boltzmann equation,
Larger cross section → smaller relic abundnace
Cross section of WIMPs 𝜎𝑣 ∼ 10 cm s
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Minimal Supersymmetric Standard Model (MSSM)
SUPERSYMMETRIC DARK MATTER 12MINSEOK CHO
MSSM
= Standard model + Higgs doublet + SUSY partners
MSSM follows the gauge symmetry SU(3) × SU(2) × U(1)
R-parity : 𝑅 = −1
𝑅 = 1 for ordinary SM particles
𝑅 = −1 for superpartners
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Minimal Supersymmetric Standard Model (MSSM)
SUPERSYMMETRIC DARK MATTER 13MINSEOK CHO
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Annihilation Cross-section
SUPERSYMMETRIC DARK MATTER 14
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Detection of WIMPs1. 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 raykeV - MeV cosmic ray in 100 events per day per kilogram
SUPERSYMMETRIC DARK MATTER 15MINSEOK CHO
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Detection of WIMPs2. 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
SUPERSYMMETRIC DARK MATTER 16MINSEOK CHO