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

Supersymmetric Dark Matter Minseok Cho KAIST December 07, 2019 1 SUPERSYMMETRIC DARK MATTER

Table of Contents 1. Dark Matter 2. Relic Abundance of WIMPs 3. Minimal Supersymmetric Standard Model (MSSM) 4. Detection of WIMPs 2 SUPERSYMMETRIC DARK MATTER

Evidence for Existence of Dark Matter Fritz Zwicky Coma Cluster 3 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Evidence for Existence of Dark Matter Vera Rubin Rotation Curve of NGC 6503 4 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Nonbaryonic Dark Matter Density parameter : �� � 𝜍 � = ��� � open universe, expand forever flat universe close universe, halt expanding and recollapse 5 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Nonbaryonic Dark Matter To explain abundance of Helium, Deuterium, and Lithium � ) � � Measurements suggest ��� � (WMAP, in LCDM model) � Bulk of dark matter is nonbaryonic 6 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

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. 7 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Relic Abundance of WIMPs Relic Abundance : how many particles remain from the early universe 𝑕 �� = 2𝜌 � � 𝑔 𝑞 𝑒 � 𝑞 𝑜 � �� ∝ 𝑈 � For 𝑈 ≫ 𝑛 � , 𝑜 � ⁄ exp − 𝑛 � 𝑈 �� ∝ 𝑕 𝑛 � 𝑈 2𝜌 � � For 𝑈 ≪ 𝑛 � , 𝑜 � ⁄ ⁄ But, the universe is not completely in thermal equilibrium 8 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Relic Abundance of WIMPs For 𝑈 ≫ 𝑛 � , 𝜓𝜓̅ ↔ 𝑦𝑦̅ 𝜓 is abundant and annihilation is active Annihilation rate : Γ = 𝑜 � 𝜏𝑤 When Γ = 𝐼 , 𝜓 stops to annihilate (freeze out) 9 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Relic Abundance of WIMPs In freeze-out condition 𝑜 � 𝑡 ⁄ � = 𝑜 � 𝑡 ⁄ � = Γ ⁄ 𝜏𝑤 𝑡 = 𝐼 ⁄ 𝜏𝑤 𝑡 ⁄ � � ≃ 100 � 𝑛 � 𝑛 �� 𝑕 ∗ 𝜏𝑤 Then Ω � ℎ � = 𝑛 � 𝑜 � 𝜍 � ≃ (3 × 10 �� cm � s �� / 𝜏𝑤 ) ⁄ 10 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Relic Abundance of WIMPs By the Boltzmann equation, 𝑒𝑜 � � − 𝑜 � �� � 𝑒𝑢 + 3𝐼𝑜 � = − 𝜏𝑤 𝑜 � Larger cross section → smaller relic abundnace Cross section of WIMPs 𝜏𝑤 ∼ 10 ��� cm � s �� 11 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Minimal Supersymmetric Standard Model (MSSM) 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 12 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Minimal Supersymmetric Standard Model (MSSM) 13 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

Annihilation Cross-section 14 SUPERSYMMETRIC DARK MATTER

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 15 MINSEOK CHO SUPERSYMMETRIC DARK MATTER

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 16 MINSEOK CHO SUPERSYMMETRIC DARK MATTER