Dark Radiation from Particle Decay

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1 Dark Radiation from Particle Decay Jörn Kersten University of Hamburg Based on Jasper Hasenkamp, JK, JCAP 08 (2013), 024 [arxiv: ] Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 1 / 19

2 Outline 1 Introduction 2 Dark Radiation from Late Decays 3 Constraints for Model Building Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 2 / 19

3 1 Introduction 2 Dark Radiation from Late Decays 3 Constraints for Model Building Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 3 / 19

4 Dark Radiation Radiation = relativistic particles Dark radiation: relativistic particles γ, ν SM Energy density (after e + e annihilation at T 0.5 MeV) [ ( ) ] 7 4 Tν ρ rad 1 + N eff ρ γ 8 T T T γ ρ γ = π2 15 T 4 N eff : effective number of neutrino species Standard Model: N eff = Existence of dark radiation N eff N eff > 0 ρ DR = 0.13 N eff ρ SM rad Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 4 / 19

5 Observable Effects Big Bang Nucleosynthesis (BBN) ρ rad faster expansion more n available for D fusion more 4 He N eff = at 95% CL 0.7 Izotov, Thuan, arxiv: N eff 1 at 95% CL Mangano, Serpico, arxiv: Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 5 / 19

6 Observable Effects Big Bang Nucleosynthesis (BBN) ρ rad faster expansion more n available for D fusion more 4 He N eff = at 95% CL 0.7 Izotov, Thuan, arxiv: N eff 1 at 95% CL Mangano, Serpico, arxiv: Cosmic Microwave Background (CMB) Increased Silk damping reduced power on small scales Hou et al., arxiv: Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 5 / 19

7 Results from the CMB N eff = 1.51 ± 0.75 at 68% CL ACT, arxiv: N eff = 0.81 ± 0.42 at 68% CL SPT, arxiv: N eff = at 95% CL Planck, arxiv: N eff = at 95% CL using H 0 from HST Planck, arxiv: N eff < 0.71 at 95% CL Hojjati et al., arxiv: N eff = 0.61 ± 0.30 at 68% CL Hamann, Hasenkamp, arxiv: Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 6 / 19

8 1 Introduction 2 Dark Radiation from Late Decays 3 Constraints for Model Building Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 7 / 19

9 New Physics in the Later Early Universe Late decays: after BBN, before recombination affect only CMB Mother 2 light, weakly interacting daughters Masses m, m 1 < m 2 δ m m 2 m 2 Daughters form dark radiation while relativistic Heavier daughter could form dark matter Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 8 / 19

10 New Physics in the Later Early Universe Late decays: after BBN, before recombination affect only CMB Mother 2 light, weakly interacting daughters Masses m, m 1 < m 2 δ m m 2 m 2 Daughters form dark radiation while relativistic Heavier daughter could form dark matter Examples: Gravitino axion + axino (Γ m 3 3/2 /M2 Pl ) Sneutrino gravitino + neutrino Modulino sneutrino + neutrino, axion + axino,... Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 8 / 19

11 Connecting N eff and Particle Physics N eff measured know ρ DR = 0.13 N eff ρ SM rad Goal: Constrain model parameters Ω: Energy density of the mother Lifetime τ (equivalently, temperature at decay T d ) δ: Mass hierarchy between mother and heavier daughter Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 9 / 19

12 Connecting N eff and Particle Physics N eff measured know ρ DR = 0.13 N eff ρ SM rad Goal: Constrain model parameters Ω: Energy density of the mother Lifetime τ (equivalently, temperature at decay T d ) δ: Mass hierarchy between mother and heavier daughter Two-body decay kinematics for m 1 m 2 : ρ DR (T d ) = N DR 2 (δ + 1) 2 1 (δ + 1) 2 ρ(t d ) Ω = Ω( N eff, τ, δ) N DR = 1, 2: number of relativistic dark particles during CMB times Free parameters in the following: τ, δ Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 9 / 19

13 Constraints from Dark Matter Density Today s density of heavier daughter Ω 2 Ω DM lower limits Decay before matter-radiation equality at t eq : δ 0.3 N eff ( teq τ ) 1 2 Decay after matter-radiation equality (now also Ω < Ω DM ): δ 0.15 N eff ( teq τ ) 2 3 Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 10 / 19

14 Constraints from Dark Matter Density min Τ from different requirements 10 7 t 2 nr min t eq tcmb 10 5 t Γ dpl 10 3 min t bbn t e e end t bbn Τ s Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 10 / 19

15 Free Streaming of Heavier Daughter Heavier daughter emitted with finite velocity washes out structure on scales smaller than free-streaming scale λ fs 2 = t0 τ v 2 a dt Limit from Lyman-α forest: λ fs 2 1 Mpc Abazajian, arxiv:astro-ph/ ; Viel et al., arxiv: ; Boyarsky et al., arxiv: Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 11 / 19

16 Free Streaming of Heavier Daughter Heavier daughter emitted with finite velocity washes out structure on scales smaller than free-streaming scale λ fs 2 = t0 τ v 2 a dt 50 Limit from Lyman-α forest: λ fs 2 1 Mpc Abazajian, arxiv:astro-ph/ ; Viel et al., arxiv: ; Boyarsky et al., arxiv: Λ 2 fs min Mpc tcmb teq dpl t Γ 1 t nr 2 min Heavier daughter too hot to form dark matter (or N eff 1) Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 11 / 19

17 Hot Dark Matter Constraint Maximum amount of hot dark matter Ω Ω DM (corresponding to m ν < 0.44 ev Hamann et al., arxiv: ) lower limits on δ rise by factor 25 Decay before matter-radiation equality at t eq : δ 7 N eff ( teq τ Decay after matter-radiation equality: δ 3.5 N eff ( teq τ ) 1 2 ) 2 3 Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 12 / 19

18 Hot Dark Matter Constraint min Τ from different requirements 10 7 t 2 nr min t eq tcmb 10 5 t Γ dpl 10 3 min t bbn t e e end t bbn Τ s Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 12 / 19

19 Hot Dark Matter Opportunities 1 Imagine conflict between future measurements: Cosmology ( m ν ) cosmo > 0 observed Laboratory upper limit < ( m ν ) cosmo Indication for hot dark matter ν from decay 2 Heavier daughter may become non-relativistic during CMB times observable consequences for CMB likely Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 13 / 19

20 Two Decay Modes 1 Mother φ + φ, branching ratio B 1 2 Mother ψ + ψ, branching ratio B 2 Daughter masses m 1 < m 2 x 2 m 2 m Lighter daughter forms dark radiation Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 14 / 19

21 Two Decay Modes 1 Mother φ + φ, branching ratio B 1 2 Mother ψ + ψ, branching ratio B 2 Daughter masses m 1 < m 2 x 2 m 2 m Lighter daughter forms dark radiation Examples: Saxion axion + axion, axino + axino Modulus gravitino + gravitino, axion + axion Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 14 / 19

22 Adjustable Free Streaming B 2 allows to adjust Ω 2 no dark matter density constraint on x 2 λ fs 2 arbitrary x ( B ( ) Mpc ( τ λ fs s ) λ fs Mpc Heavier daughter may form dark matter Can be cold or warm ) 0.5 N 1 eff ( ΩDM h 2 ) Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 15 / 19

23 Adjustable Free Streaming 10 3 end t bbn s t cmb x t e e Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 15 / 19

24 Solution of the Missing Satellites Problem Simulations of structure formation more galactic satellites than observed Problem may well be solved by astrophysics... or by warm dark matter with 0.2 Mpc λ fs 1 Mpc Colín et al., arxiv:astro-ph/ ; Lin et al., arxiv:astro-ph/ possible in two-decay-mode scenario Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 16 / 19

25 1 Introduction 2 Dark Radiation from Late Decays 3 Constraints for Model Building Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 17 / 19

26 Constraints on Decays into Standard Model Particles Br(Mother SM + SM) 0 Change of primordial abundances from BBN Jedamzik, arxiv:hep-ph/ Spectral distortions of the CMB Hu, Silk, PRL 70 (1993); Chluba, Sunyaev, arxiv: Change of ionization history Slatyer, arxiv: strict upper limits on branching ratio Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19

27 Constraints on Decays into Standard Model Particles 10 0 Direct B em max Τ from BBN constraints B em max t cmb t Γ dpl 10 8 t bbn end t bbn t eq Τ s Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19

28 Constraints on Decays into Standard Model Particles Direct B max vis Τ from CMB constraints t Γ dpl max B vis t bbn end t bbn t cmb t eq Τ s Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19

29 Constraints on Decays into Standard Model Particles Br(Mother SM + SM) 0 Change of primordial abundances from BBN Jedamzik, arxiv:hep-ph/ Spectral distortions of the CMB Hu, Silk, PRL 70 (1993); Chluba, Sunyaev, arxiv: Change of ionization history Slatyer, arxiv: strict upper limits on branching ratio... even if only suppressed decay possible (loop, 3- or 4-body decay) Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19

30 Constraints on Decays into Standard Model Particles B max had Τ from BBN constraints in considered scenarios end t bbn max B had t cmb t Γ dpl 10 8 t bbn t eq Τ s Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19

31 Conclusions Dark universe may contain dark radiation Production in late decays different impact on BBN and CMB Energy density of mother determined by N eff, τ, δ Single dark decay mode: heavier daughter too hot for dark matter Two dark decay modes: heavier daughter may form dark matter and solve missing satellites problem Severe constraints on branching ratio into Standard Model particles input for construction of concrete models Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 19 / 19

32 Effects on the Cosmic Microwave Background (CMB) ρ rad later matter-radiation equality 1 st /3 rd peak ratio no change ρ m t eq unchanged ρ rad sound horizon r s 1/H Peak positions no change of angular size θ s = rs D A D A 1/H (by ρ Λ ) Remaining effect: increased Silk damping reduced power on small scales Hou et al., arxiv: Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 20 / 19