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C. W. Kim
KIAS
The Johns Hopkins
Neutrinos in Cosmology
October 27, 2008
It is truly remarkable that we should have come so far in determining, from the passive collection of a small fraction of the photons that chance to come our way, the properties of neutrinos better than nuclear/particle physics has ever attempted in many decades. (Charles Bennett in Nature in 2006) 1
Pauli to his friend Baade:1930
“Today I did something a physicist should never do. I predicted something which will never be observed experimentally…”
Neutrino : Pauli’particle
2
Fundamental Building Blocks
Quarks u c t
d s b (3 Colors )
Leptons
e μ τ
ν ν νe μ τ Neutrinos
3
4
Important Issues
1. Mass
2. Mixing
3. Number of flavors
4. CP violation
Oscillations
Lepto-genesis
5
From present evidences of oscillations from experiments measuring
atmospheric, solar, reactor and accelerator neutrinos
We know that flavour neutrino oscillations exist
Weak e.s.Mass e.s.
6
Neutrinos are mixed.
Production and detection
via Weak eigenstates
Propagation (Equ. Of motion)
via Mass eigenstates
νν
νµ
e
τ
=
U U Ue1 e2 e3
U U Uµ1 µ2 µ3
U U Uτ1 τ2 τ3
•
νν
ν2
1
3
(( They are massive. )
7
Mixing Matrix : Nuclear/Particle Physics
3
√
√2 2
2 22
sin θ13 ei δ
U≈
θ θθ ≈ ≈ < 35 4512 23 13
13o oo
Bi-large mixing with U =0, θ = θ , θ = θ = π /6e3 ATM23 12 SOL
√21
1
√2
√3 1
√22√21
√2
√3 1
2
8
• Tritium beta decay: measurements of endpoint energy
m(νe) < 2.2 eV (95% CL) Mainz
Future experiments (KATRIN) m(νe) ~ 0.2-0.3 eV
• Neutrinoless double beta decay: if Majorana neutrinos
experiments with 76Ge and other isotopes: ImeeI < 0.4hN eV
Laboratory mass measurement experiments
e -33 eHe H
-2e2)Z(A, Z)(A,
9
m ( ν ) < 0.17 Mev (95%CL)
from π → μ + ν
m ( ν ) < 18.2 MeV (95%CL)
from τ → 3 π + 2 π + ν
μ
μ
τ
+τ
Particle Physics
10
11
If ∑ m j < 8 x 10 eV, the inverted hierarchy is ruled out !!
There are at least two neutrinos which are heavier than 8 X 10 eV .
-2
-3
No lower bound for the lightest neutrino !! 12
Tritium β
decay< 2.2 eV
2/1
22
iiei mUm
e
Neutrinoless
double betadecay<0.4-1.6 eV
i
ieiee mUm 2
<0.3-1.5 eV Cosmology
iim~
Absolute Mass Searches
13
T < eVT ~ MeV
Formation of Large Scale Structures
LSS
Cosmic Microwave Background
CMB
PrimordialNucleosynthesis
BBN
No flavour sensitivity Neff & mννevs νμ,τ Neff
Relic neutrinos influence several cosmological epochs
14
15
photons
neutrinos
cdm
baryons
Λ
Evolution of the background densities
m3=0.05 eV
m2=0.009 eV
m1≈ 0 eV
16
Number of Neutrino Flavors
17
Number of Neutrino flavors(in the Universe)
Decay of Z : data) (LEP 008.0984.2 N
N influences H :
Slow expansion ⇒ less He. Fast expansion ⇒ more He
+ 1.4- 1.2
4
4
(Particles such as sterile neutrinos are not included. m < 45 GeV).
BBN : N = 3.1 95% CL ( He + D data)
(Neutron life time = 14.76 minutes)
eff
eff
N = 3 ⇒ N = 3.046 (standard value)
(SM and neutrino oscillations : ν v.s. ν )
4
ν ν
e μ,τ
*
( Not relic!)*
18
N
inv
( Z → l l )
= 2.9840 ± 0.0082
This is valid for m < 45 GeV.
Particle Physics
Γ = Nν Γ( Z → ν ν )
= νinvΓ
ν
( Z → )ΓΓ ν ν
l l( Z → )
Z boson:
SM
19
Number of Neutrino flavors(in the Universe)
Decay of Z : data) (LEP 008.0984.2 N
N influences H :
Slow expansion ⇒ less He. Fast expansion ⇒ more He
+ 1.4- 1.2
4
4
(Particles such as sterile neutrinos are not included. m < 45 GeV).
BBN : N = 3.1 95% CL ( He + D data)
(Neutron life time = 14.76 minutes)
eff
eff
N = 3 ⇒ N = 3.046 (standard value)
(SM and neutrino oscillations : ν v.s. ν )
4
ν ν
e μ,τ
*
( Not relic!)*
20
T ( ) ~ 2 MeV : CC & NC
T ( ) ~ 3 MeV : NC only
No μ & τ in plasma
dec
dec νe
νμ ,τ
Neutrino Oscillations in plasma before decoupling
21
311
4
8
71
158
73
15
3/44
24
2
r TT
Ω Ω Ω Ω = 1 Λ m γ ν+ + +
*
To be determined22
1/3
411
T
T
ν
γ
23
311
4
8
71
158
73
15
3/44
24
2
r TT
Ω Ω Ω Ω = 1 Λ m γ ν+ + +
*
To be determined 24
Effect of Neff at later epochsNeff modifies the radiation content: Changes the epoch of matter-radiation equivalence
Galaxy Mass SpectrumAnisotropy Spectrum
25
WMAP 3b
26
↑
m
WMAP 5
27
Results: WMAP 5-year data
N eff = 4.4 + 1.5 (68%C.L.)_
1.9 < N < 7.8 (95%C.L.)eff
even after breaking degeneracy using
BAO, SN and HST28
Neutrino Mass Values
29
eV 93.2
mh Ω i
i2
ν
eV 15 m 0.3Ω Ω
eV 46 m 1 Ω eV 93.2
mhΩ
iimν
iiν
ii
2ν
MpceV 30
m 41
-1
ν
Neutrino Free Streaming
Φ
b, cdm
ν
30
30
mν
32
33
5
34
Parameter degeneracy: Neutrino mass and wIn cosmological models with more parameters the neutrino mass bounds can be relaxed.
Ex: quintessence-like dark energy with ρDE=w pDE
WMAP Coll, astro-ph/0603449
Λ
35
WMAP 5 year Data
WMAP -5
WMAP5 plus
BAO + SN
36
Neutrino Mass from Cosmology
1. CMB alone: Σm < 1.5 eV (95% CL)
2. With BAO and SN:
Σm < 0.61 eV (95% CL) with w = 1
Σm
ν
ν
ν < 0.66 eV (95% CL) without w = 1
( Remember that Σm and H are degenerate for CMB
but no degeneracy between w and Σ m )
ν o
3. To go beyond, we need SDSS, Lyman-α, … But bias, …
ν
37
Neutrinos as HDM
● As long as HDM is relativistic, HDM perturbations within the horizon
are erased by “ Free – Streaming”.
● Free-streaming stops when HDM becomes
non-relativistic at Zn-r .→ If HDM dominates, top-down structure
formation but, observation → bottom-up.
→ limit on Σ m j j
P(k)ΔP(k)
~ (1 eV
Σ m j j) (
ΩM h2 )0.10● _
Reduces small scale amplitude of Mass Fluctuations38
Horizon distance at matter = radiationEnters in matter dominated era
Enters in rad. Dominated era
Σ m = 1 eVi
39
13
40
Neutrino Mass from Cosmology
1. CMB alone: Σm < 1.5 eV (95% CL)
2. With BAO and SN:
Σm < 0.61 eV (95% CL) with w = 1
Σm
ν
ν
ν < 0.66 eV (95% CL) without w = 1
( Remember that Σm and H are degenerate for CMB but
no degeneracy between w and Σ m )ν o
3. To go beyond, we need SDSS, Lyman-α, sdFGRs … But galaxy bias, … :Non-linear effects
ν
Let’s pull it down to 0.08 eV
(Two ν are heavier than this value)
Star Gazer
m ν
WMAP
Lyman-α forest data
Absorption lines in the spectrum of distant quasars due to intermediate H clouds which absorb Lyman-α lines at
λα = 1215.67 Ao
Lyman-α forest data
Absorption lines in the spectrum of distant quasars due to intermediate H clouds which absorb Lyman-α lines at
λα = 1215.67 Ao
Layers of H Clouds ⇒ forest
Lyman-α forest spectrum from Q2139-4434 (z= 3.23)
Lyman-α forest data
Absorption lines in the spectrum of distant quasars due to intermediate H clouds which absorb Lyman-α lines at
λα = 1215.67 Ao
Layers of H Clouds ⇒ forest
Absorption lines ⇒ Study of change of power spectrum of δρ/ρ for small λ
But this is very difficult and model dependent ( bias ).
ΔP(k)/P(k) ~ -10 Ω / Ω : a factor of 2 suppression for Σm = 1 eV(7% of CDM)
νo
Mo
j
WMAP3
* m < 0.7 eV (95% CL)
*H and m degeneracy
νO
Unknown m ⇒ one of the largest systematic errors for estimating cosmological parameters from CMB
* m > 0.3 eV favors smaller Hubble constant.
ν
( Clean and Robustν
ν
*To improve the limit, need data other than WMAP !
SDSS, 2dFGRS, Lyman-α forest, Gravitational lensing,…
But inherent systematic errors need to be understood.
Conclusions
even with WMAP1 alone)