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