Dark Radiation from Particle Decay Jörn Kersten University of Hamburg Based on Jasper Hasenkamp, JK, JCAP 08 (2013), 024 [arXiv:1212.4160] Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 1 / 19
Dark Radiation from Particle Decay
Jörn Kersten
University of Hamburg
Based on Jasper Hasenkamp, JK, JCAP 08 (2013), 024 [arXiv:1212.4160]
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 1 / 19
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
1 Introduction
2 Dark Radiation from Late Decays
3 Constraints for Model Building
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 3 / 19
Dark Radiation
Radiation = relativistic particlesDark radiation: relativistic particles 6= �, ⌫SM
Energy density (after e+e� annihilation at T ⇠ 0.5 MeV)
⇢rad ⌘"
1 + Neff78
✓T⌫
T
◆4#⇢�
T ⌘ T�
⇢� = ⇡2
15T 4
Neff: effective number of neutrino speciesStandard Model: Neff = 3.046Existence of dark radiation , �Neff ⌘ Neff � 3.046 > 0
⇢DR = 0.13�Neff ⇢SMrad
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 4 / 19
Observable Effects
Big Bang Nucleosynthesis (BBN)⇢rad " faster expansion more n available for D fusion more 4HeNeff = 3.8+0.8
�0.7 at 95% CLIzotov, Thuan, arXiv:1001.4440
�Neff 1 at 95% CLMangano, Serpico, arXiv:1103.1261
Cosmic Microwave Background (CMB)Increased Silk damping reduced power on small scalesHou et al., arXiv:1104.2333
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 5 / 19
Observable Effects
Big Bang Nucleosynthesis (BBN)⇢rad " faster expansion more n available for D fusion more 4HeNeff = 3.8+0.8
�0.7 at 95% CLIzotov, Thuan, arXiv:1001.4440
�Neff 1 at 95% CLMangano, Serpico, arXiv:1103.1261
Cosmic Microwave Background (CMB)Increased Silk damping reduced power on small scalesHou et al., arXiv:1104.2333
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 5 / 19
Selected Results from the CMB
�Neff = 1.51 ± 0.75 at 68% CL ACT, arXiv:1009.0866
�Neff = 0.81 ± 0.42 at 68% CL SPT, arXiv:1105.3182
�Neff = 0.31+0.68�0.64 at 95% CL Planck, arXiv:1303.5076
�Neff = 0.47+0.48�0.45 at 95% CL using H0 from HST Planck, arXiv:1303.5076
�Neff < 0.71 at 95% CL Hojjati et al., arXiv:1304.3724
�Neff = 0.61 ± 0.30 at 68% CL Hamann, Hasenkamp, arXiv:1308.3255
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 6 / 19
1 Introduction
2 Dark Radiation from Late Decays
3 Constraints for Model Building
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 7 / 19
New Physics in the Later Early Universe
Late decays: after BBN, before recombination affect only CMBMother ! 2 weakly interacting daughtersMasses m, m1 < m2
� ⌘ m � m2m2
Daughters form dark radiation while relativisticHeavier daughter could form dark matter
Examples:Gravitino ! axion + axino (� ⇠ m3
3/2/M2Pl)
Sneutrino ! gravitino + neutrinoModulino ! sneutrino + neutrino, axion + axino, . . .
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 8 / 19
New Physics in the Later Early Universe
Late decays: after BBN, before recombination affect only CMBMother ! 2 weakly interacting daughtersMasses m, m1 < m2
� ⌘ m � m2m2
Daughters form dark radiation while relativisticHeavier daughter could form dark matterExamples:
Gravitino ! axion + axino (� ⇠ m33/2/M2
Pl)Sneutrino ! gravitino + neutrinoModulino ! sneutrino + neutrino, axion + axino, . . .
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 8 / 19
Connecting �Neff and Particle Physics
�Neff measured know⇢DR = 0.13�Neff ⇢
SMrad
Goal: Constrain model parameters⌦: Energy density of the motherLifetime ⌧ (equivalently, temperature at decay Td)�: Mass hierarchy between mother and heavier daughter
Two-body decay kinematics for m1 ⌧ m2:
⇢DR(Td) =NDR
2(� + 1)2 � 1(� + 1)2 ⇢(Td) ⌦ = ⌦(�Neff, ⌧, �)
NDR = 1, 2: number of relativistic dark particles during CMB times
Free parameters in the following: ⌧ , �
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 9 / 19
Connecting �Neff and Particle Physics
�Neff measured know⇢DR = 0.13�Neff ⇢
SMrad
Goal: Constrain model parameters⌦: Energy density of the motherLifetime ⌧ (equivalently, temperature at decay Td)�: Mass hierarchy between mother and heavier daughter
Two-body decay kinematics for m1 ⌧ m2:
⇢DR(Td) =NDR
2(� + 1)2 � 1(� + 1)2 ⇢(Td) ⌦ = ⌦(�Neff, ⌧, �)
NDR = 1, 2: number of relativistic dark particles during CMB times
Free parameters in the following: ⌧ , �
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 9 / 19
Constraints from Dark Matter Density
Today’s density of heavier daughter ⌦2 ⌦DM lower limits
Decay before matter-radiation equality at teq:
� & 0.3�Neff
✓teq
⌧
◆ 12
Decay after matter-radiation equality (now also ⌦ < ⌦DM):
� & 0.15�Neff
✓teq
⌧
◆ 23
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 10 / 19
Constraints from Dark Matter Density
10-1 101 103 105 107 109 1011 1013 1015 1017
10-3
10-1
101
103
105
107
t@sD
d min
dmin HtL from different requirements
tbbnendtbbn te+ e-
teq
tgdpl
Ht2nr Lmintcmb
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 10 / 19
Free Streaming of Heavier Daughter
Heavier daughter emitted with finite velocity washes out structure on scales smaller than free-streaming scale
�fs2 =
Z t0
⌧
v2a
dt
Limit from Lyman-↵ forest:
�fs2 . 1 Mpc
Abazajian, arXiv:astro-ph/0512631;Viel et al., arXiv:0709.0131;Boyarsky et al., arXiv:0812.0010
Heavier daughter too hot to form dark matter (or �Neff ⌧ 1)
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 11 / 19
Free Streaming of Heavier Daughter
Heavier daughter emitted with finite velocity washes out structure on scales smaller than free-streaming scale
�fs2 =
Z t0
⌧
v2a
dt
Limit from Lyman-↵ forest:
�fs2 . 1 Mpc
Abazajian, arXiv:astro-ph/0512631;Viel et al., arXiv:0709.0131;Boyarsky et al., arXiv:0812.0010
109 1011 1013 1015 1017
1
2
5
10
20
50
t@sD
Hl 2fs Lmin@Mp
cD
Hl2fsLmin =l2fsHdmin L
teq tgdpl
Ht2nr Lmin
tcmb
Heavier daughter too hot to form dark matter (or �Neff ⌧ 1)
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 11 / 19
Hot Dark Matter Constraint
Maximum amount of hot dark matter ⌦2 . 0.04⌦DM(corresponding to
Pm⌫ < 0.44 eV Hamann et al., arXiv:1003.3999)
lower limits on � rise by factor 25
Decay before matter-radiation equality at teq:
� & 7�Neff
✓teq
⌧
◆ 12
Decay after matter-radiation equality:
� & 3.5�Neff
✓teq
⌧
◆ 23
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 12 / 19
Hot Dark Matter Constraint
10-1 101 103 105 107 109 1011 1013 1015 1017
10-3
10-1
101
103
105
107
t@sD
d min
dmin HtL from different requirements
tbbnendtbbn te+ e-
teq
tgdpl
Ht2nr Lmintcmb
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 12 / 19
Hot Dark Matter Opportunities
1 Imagine conflict between future measurements:Cosmology (
Pm⌫)cosmo > 0 observed
Laboratory upper limit < (P
m⌫)cosmo
Indication for hot dark matter 6= ⌫ 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
Two Decay Modes
1 Mother ! �+ �, branching ratio B12 Mother ! + , branching ratio B2
Daughter masses m1 < m2
x2 ⌘ m2m
Lighter daughter forms dark radiation
Examples:Saxion ! axion + axion, axino + axinoModulus ! gravitino + gravitino, axion + axion
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 14 / 19
Two Decay Modes
1 Mother ! �+ �, branching ratio B12 Mother ! + , branching ratio B2
Daughter masses m1 < m2
x2 ⌘ m2m
Lighter daughter forms dark radiationExamples:
Saxion ! axion + axion, axino + axinoModulus ! gravitino + gravitino, axion + axion
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 14 / 19
Adjustable Free Streaming
B2 allows to adjust ⌦2 no dark matter density constraint on x2 �fs
2 arbitrary
x2 ' 0.1
0.4 Mpc�fs
2
!1.2 ⇣ ⌧
105 s
⌘0.5
B2 ' 5.6 · 10�3
�fs
20.4 Mpc
!�N�1
eff
✓⌦DMh2
0.1286
◆
Heavier daughter may form dark matter Can be cold or warm
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 15 / 19
Adjustable Free Streaming
101 103 105 107 109 1011
101
103
t@sD
x 2-1
x 2-1Hl2fsL
te+ e-
tbbnend tcmb8¥105 s
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 15 / 19
Solution of the Missing Satellites Problem
Simulations of structure formation more galactic satellites than observedProblem may well be solved by astrophysics. . . or by warm dark matter with0.2 Mpc . �fs . 1 MpcColín et al., arXiv:astro-ph/0004115;Lin et al., arXiv:astro-ph/0009003
possible in two-decay-mode scenario
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 16 / 19
1 Introduction
2 Dark Radiation from Late Decays
3 Constraints for Model Building
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 17 / 19
Constraints on Decays into Standard Model Particles
Br(Mother ! SM + SM) 6= 0
Change of primordial abundances from BBNJedamzik, arXiv:hep-ph/0604251; Kawasaki, Kohri, Moroi, arXiv:astro-ph/0408426
Spectral distortions of the CMBHu, Silk, PRL 70 (1993); Chluba, Sunyaev, arXiv:1109.6552
Change of ionization historySlatyer, arXiv:1211.0283
strict upper limits on branching ratio
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19
Constraints on Decays into Standard Model Particles
10-1 101 103 105 107 109 1011 1013 1015 101710-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
t@sD
B emmax
Direct BemmaxHtL from BBN constraints
tbbnendtbbn teq
tgdpltcmb
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19
Constraints on Decays into Standard Model Particles
10-1 101 103 105 107 109 1011 1013 1015 101710-1110-1010-910-810-710-610-510-410-310-210-1100
t@sD
B vismax
Direct BvismaxHtL from CMB constraints
tbbnendtbbn teq
tgdpl
tcmb
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19
Constraints on Decays into Standard Model Particles
Br(Mother ! SM + SM) 6= 0
Change of primordial abundances from BBNJedamzik, arXiv:hep-ph/0604251; Kawasaki, Kohri, Moroi, arXiv:astro-ph/0408426
Spectral distortions of the CMBHu, Silk, PRL 70 (1993); Chluba, Sunyaev, arXiv:1109.6552
Change of ionization historySlatyer, arXiv:1211.0283
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
Constraints on Decays into Standard Model Particles
10-1 101 103 105 107 109 1011 1013 1015 101710-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
t@sD
B hadmax
BhadmaxHtL from BBN constraints in considered scenarios
tbbnend
tbbn teq
tgdpltcmb
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 18 / 19
Conclusions
Dark universe may contain dark radiationProduction in late decays different impact on BBN and CMBEnergy density of mother determined by �Neff, ⌧ , �
Single dark decay mode: heavier daughter too hot for dark matterTwo dark decay modes: heavier daughter may form dark matterand solve missing satellites problemSevere constraints on branching ratio into Standard Modelparticles input for construction of concrete models
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 19 / 19
Effects on the Cosmic Microwave Background (CMB)
⇢rad " later matter-radiationequality1st/3rd peak ratio no change ⇢m " teq unchanged⇢rad " sound horizon rs / 1/H #Peak positions no change ofangular size ✓s = rs
DA DA / 1/H #
(by ⇢⇤ ")Remaining effect:increased Silk damping reduced power on small scalesHou et al., arXiv:1104.2333
Jörn Kersten (Uni Hamburg) Dark Radiation from Particle Decay 20 / 19