Post on 03-Jan-2016
description
RELIC NEUTRINOS: NEUTRINO PROPERTIES FROM COSMOLOGY
Sergio Pastor (IFIC)
ν
Massive neutrinos
Standard neutrinos
Extra radiation and Neutrino asymmetries
RELIC NEUTRINOS: OUTLINE
RELIC NEUTRINOS
Massive neutrinos
Standard neutrinos
Extra radiation and Neutrino asymmetries
Neutrinos in equilibrium
fν(p,T)=fFD(p,T)1e
1T)(p,f p/T
Standard Relic Neutrinos
-αα
-α
-α
βαβα
βαβα
ee
ee
νν
νν
νννν
νννν
Tν = Te = Tγ
1 MeV T mμ
Neutrinos in Equilibrium
Neutrinos in equilibrium
fν(p,T)=fFD(p,T)1e
1T)(p,f p/T
Standard Relic Neutrinos
rate expansion Hubble processes weak of rate
MeV 1T 3M8π
TG HΓ dec2p
5Fν
Neutrino decoupling
Decoupled Neutrinos
fν(p)=fFD(p,Tν)
Tdec(νe) ~ 2.3 MeVTdec(νμ,τ) ~ 3.5 MeV
Neutrino decoupling
At T~me, electron-positron pairs annihilate
heating photons but not the decoupled neutrinos
Decoupled neutrinos stream freely until non-relativistic
1/3
411
T
T
ν
γ
γγ -ee
Neutrino and Photon temperatures
• Number density
• Energy density
Neutrinos after decoupling
flavor per
cm )( 112
present at3- 3
23
3
11
3(6
11
9
2 CMBγi
ννν Tπ
)ζn)(p,Tf
π)(
pdn
i
CMB
iννν
nm
T
)(p,Tfπ)(
pdmp
i
i
423/4
3
322
3011
4
4
21
2
Massless
Massive mν>>T
Neutrinos and Cosmology
Neutrinos influence several cosmological scenarios
Primordial
Nucleosynthesis
BBN
Cosmic Microwave Background
CMB
Formation of Large Scale Structures
LSS
z~1010 z~1000
RELIC NEUTRINOS
Massive neutrinos
Standard neutrinos
Extra radiation and Neutrino asymmetries
At T<<me, the radiation content of the Universe is
Effective number of relativistic neutrino speciesTraditional parametrization of the energy densitystored in relativistic particles
Neff is not exactly 3 for standard neutrinos (if mν<<T)
Relativistic particles in the Universe
data) (LEP 008.0984.2 N
But, since Tdec(νe) ~ me, neutrinos slightly share a small part of the entropy release
At T~me, e+e- pairs annihilate heating photonsγγ -ee
Non-instantaneous neutrino decoupling
But, since Tdec(νe) ~ me, neutrinos slightly share a small part of the entropy release
Tν 0.15% largerρ(νe) 1% larger
ρ(νμ,τ) 0.5% larger
fν=fFD(p,Tν)[1+δf(p)]
Non-instantaneous decoupling + QED corrections to e.m. plasma
Neff=3.0395 Mangano et al 2002
Non-instantaneous neutrino decoupling
• Extra radiation can be:
scalars, pseudoscalars, sterile neutrinos (totally or partially thermalized, bulk), neutrinos in very low-energy reheating scenarios, relativistic decay products of heavy particles…
• Particular case: relic neutrino asymmetries
Constraints from BBN and from CMB+LSS
Extra relativistic particles
Produced elements: D, 3He, 4He, 7Li and
small abundances of others
BBN: Creation of light elements
Standard BBN: the baryon density is the sole parameter
Fields & Sarkar PDG 2002
BBN: Predictions vs Observations
After WMAPΩBh2=0.023±0.001
Effect of Neff on BBN
Neff fixes the expansion rate during BBN
(Neff)>0 4He
Burles, Nollett & Turner 1999
2p3M
8π H
3.4 3.2
3.0
Cyburt et al, astro-ph/0302431
BBN: allowed ranges for Neff
Hannestad astro-ph/03030760.40.3eff 2.6N
Not significantly different
from previous analyses
Lisi et al 1999, Esposito et al 2000, Burles et al 2001, Cyburt et al 2002…
Hannestad astro-ph/0303076
Hannestad astro-ph/03030760.4ΔN eff
CMB DATA: FIRST YEAR WMAP vs COBE
Map of CMBR temperature Fluctuations
T
T-),T(),Δ(
Multipole Expansion
CMB DATA: INCREASING PRECISION
Angular Power Spectrum
CMB DATA: INCREASING PRECISION
Degrees (θ) 10 1 0.1
Degrees (θ) 10 1 0.1
CMB DATA: FIRST YEAR OF WMAP
Effect of Neff on CMB
• Neff modifies the radiation content:
• Changes the epoch of matter-radiation equivalence
Pierpaoli astro-ph/0302465
CMB+LSS: allowed ranges for Neff
Crotty, Lesgourgues & SP, astro-ph/0302337
Problem: parameter degeneracies
• Set of parameters: ( Ωbh2 , Ωcdmh2 , h , ns , A , b , Neff )
• DATA: WMAP + other CMB + 2dF + HST (+ SN-Ia)
• Upper bound on h important to fix upper limit on Neff
• Flat Models
• Non-flat Models
3.72.0eff 3.5N
2.01.9eff 4.1N
3σ at 0Neff
95% CL
95% CL
Future bounds on Neff
• Next CMB data from WMAP and PLANCK (other CMB experiments on large l’s) temperature and polarization spectra
•Forecast analysis in ΩΛ=0 modelsLopez et al, PRL 82 (1999) 3952
WMAP
PLANCK
Recent analysis:Larger errors
Bowen et al 2002
ΔNeff ~ 3 (WMAP)
ΔNeff ~ 0.2 (Planck)
Neutrinos in equilibrium
fν(p,T)=fFD(p,T)1e
1T),(p,f )/T-(p
Degenerate Relic Neutrinos
/T
Relic neutrino asymmetries
nn
32
3
)3(12
1
T
T
n
nnL
42
27
15
N
Raffelt
Fermi-Dirac spectrum with temperature T and
chemical potential
More radiation
Degenerate Nucleosynthesis
If 0 , for any flavor
42
27
15
N ()>(0) 4He
Plus the direct effect on np if (e)0
e
pn
eqT
mm
p
n exp e>0 4He
Pairs (e,N) that produce the same observed abundances for larger B Kang & Steigman 1992
Hansen et al 2001 Hannestad 2003
Combined bounds BBN & CMB-LSS
4.2 22.001.0 , e
In the presence of flavor oscillations ?
Degeneracy direction (arbitrary ξe)
Flavor neutrino oscillations in the Early Universe
• Density matrix
• Mixing matrix
• Expansion of the Universe• Charged lepton background (finite T contribution)• Collisions (damping)• Neutrino background: diagonal and off-diagonal potentials
e
e
eeee
132313231223121323122312
132313231223121323122312
1313121312
ccscsscsccss
cssssccssccs
scscc
Dominant term: Synchronized Neutrino Oscillations
07.0 Effective flavor equilibrium (almost) established
BBN
Evolution in ATM + solar LMA (13=0)
Dolgov et al 2002
Synchronized neutrino oscillations
Small conversion before the onset of BBN
BBN
Evolution in ATM + solar LOW (13=0)
RELIC NEUTRINOS
Extra radiation and Neutrino asymmetries
Standard neutrinos
Massive neutrinos
Neutrinos as Dark Matter
• Neutrinos are natural DM candidates
• They stream freely until non-relativistic (collisionless phase mixing) Neutrinos are HOT Dark Matter
• First structures to be formed when Universe became matter -dominated
• Ruled out by structure formation CDM
eV 46 m 1 Ω eV 92.5
mhΩ
iiν
ii
2ν
MpceV 30
m 41
-1
ν
Neutrino Free Streaming
Neutrinos as Dark Matter
• Neutrinos are natural DM candidates
• They stream freely until non-relativistic (collisionless phase mixing) Neutrinos are HOT Dark Matter
• First structures to be formed when Universe became matter -dominated
• Ruled out by structure formation CDM
eV 46 m 1 Ω eV 92.5
mhΩ
iiν
ii
2ν
MpceV 30
m 41
-1
ν
Power Spectrum of density fluctuations
Massive Neutrinos can still be subdominant DM: limits on mν from Structure Formation
Galaxy Surveys
CMB experiments
Neutrinos as Hot Dark Matter
W. Hu
• Effect of Massive Neutrinos: suppression of Power at small scales
Max Tegmark’s homepage
www.hep.upenn.edu/~max/
Effect of massive neutrinos on the CMB and Matter Power
Spectra
2dFGRS Galaxy Survey
2dFGRS Galaxy Survey
~ 1300 M
pc
Power spectrum of density fluctuations from 2dF
2dFGRS [Elgarøy et al] 2002
Bias b2(k)=Pg(k)/Pm(k)
Non-linearity
3 degenerate massive neutrinos Σmν = 3m0`
Neutrino mass in 3-neutrino schemes
eV eV
From present evidences of atmospheric and solar neutrino oscillations
atmatm
solar
solar
m0
eV 0.008 m
eV 0.06m
2sun
2atm
Direct laboratory bounds on mν
Searching for non-zero neutrino mass in laboratory experiments
• Tritium beta decay: measurements of endpoint energy
m(νe) < 2.2 eV (95% CL) Mainz-Troitsk
• Future experiments (KATRIN) m(νe) ~ 0.3 eV
• Neutrinoless double beta decay: if Majorana neutrinos
76Ge experiments: ImeeI < 0.35 eV
e -33 eHe H
WMAP+CBI+ACBAR+2dFGRS+Lyman α Spergel et al astro-ph/0302209
Σmν < 0.71 eVΩνh2 < 0.0076
m0 < 0.23 eV
95% CL
3 degenerate massive neutrinos
Bound on mν after first year WMAP data
Pierce & Murayama hep-ph/0302131
Strumia hep-ph/0201134 (v4)
Giunti hep-ph/0302173Σmν < 0.71 eVΩνh2 < 0.0076
Small marginally allowed region
3+1 solution strongly disfavored
Is the 3+1 LSND scenario ruled out ?
22LSND eV 1 ~Δm
More conservativeΣmν < 1.01 eV
Hannestad astro-ph/0303076
Elgarøy & Lahav astro-ph/0303089
Real bound on the 3+1 LSND scenario
• Take into account the number of neutrino species
• 3+1 scenario: 4 neutrinos (including thermalized sterile)
• Calculate the bounds with Nν > 3
Abazajian 2002, di Bari 2002
Hannestad astro-ph/0303076
(also Elgarøy & Lahav, astro-ph/0303089)
3 ν4 ν
5 ν
Hannestad
95% CL
WMAP + Other CMB + 2dF + HST + SN-Ia
1 massive + 3 massless case not yet considered
Crotty, Lesgourgues & SP, in preparation
Future bounds on Σmν
• Next CMB data from WMAP and PLANCK (other CMB experiments on large l’s) temperature and polarization spectra
• SDSS galaxy survey: 106 galaxies (250,000 for 2dF)
• Forecast analysis in WMAP and ΩΛ=0 modelsHu et al, PRL 80 (1998) 5255
With current best-fit values
eV 0.1N
hΩ 0.65 Σm
0.82m
νν
eV0.37 Σm
Future bounds on Σmν
• Updated analysis: Hannestad astro-ph/0211106
• Σm detectable at 2σ if larger than
• With a galaxy survey ~10 times SDSS 0.03-0.06 eV
• From weak gravitational lensing: sensitive to both dark energy and neutrino mass. Future ~ 0.1 eV
0.45 eV (WMAP+SDSS)
0.12 eV (PLANCK+SDSS)
Abazajian and Dodelson astro-ph/0212216
Stringent limits on potential relic neutrino asymmetries from flavor equilibrium before BBN
(lξνl<0.07), fixing the cosmic neutrino density to 1%
Cosmological observables efficiently constrain some properties of (relic) neutrinos
Bounds on the radiation content of the Universe (Neff) from BBN (with ηB input from
CMB) and CMB+LSS (Neff<7 at 95%CL)
Conclusions
Bounds on the sum of neutrino masses from CMB + 2dFGRS (conservative Σmν<1 eV), with
sub-eV sensitivity in the next future