NEUTRINO MASS BOUNDS FROM COSMOLOGICAL OBSERVABLES

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NEUTRINO MASS BOUNDS FROM COSMOLOGICAL OBSERVABLES
?
XIth International Workshop on Neutrino
Telescopes, Venice Feb 2005

• Sergio Pastor (IFIC)

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NEUTRINO MASS BOUNDS FROM COSMOLOGY
Relic neutrinos
Effect of neutrino mass on cosmological
observables
Current bounds and future sensitivities
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NEUTRINO MASS BOUNDS FROM COSMOLOGY
Relic neutrinos
Effect of neutrino mass on cosmological
observables
Current bounds and future sensitivities
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Standard Relic Neutrinos
Neutrinos in equilibrium
f?(p,T)fFD(p,T)
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Neutrinos in Equilibrium
1 MeV ? T ? mµ
T? Te T?
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Neutrino decoupling
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Neutrino decoupling
Tdec(?e) 2.3 MeV Tdec(?µ,t) 3.5 MeV
Decoupled Neutrinos
f?(p)fFD(p,T?)
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Neutrino and Photon temperatures
At Tme, electron-positron pairs
annihilate heating photons but not the
decoupled neutrinos
Decoupled neutrinos stream freely until
non-relativistic
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The Cosmic Neutrino Background

• Number density
• Energy density

Massless
Massive m?gtgtT
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Neutrinos and Cosmology
Neutrinos influence several cosmological epochs
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Primordial Nucleosynthesis allowed ranges for
Neff
Non-instantaneous decoupling Flavor
Oscillations Neff3.045(5) T.Pinto et al, in
preparation
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NEUTRINO MASS BOUNDS FROM COSMOLOGY
Relic neutrinos
Effect of neutrino mass on cosmological
observables
Current bounds and future sensitivities
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CMB DATA FIRST YEAR WMAP vs COBE
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CMB DATA INCREASING PRECISION
Map of CMBR temperature Fluctuations
Multipole Expansion
Angular Power Spectrum
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Galaxy Surveys
2dFGRS
SDSS
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2dFGRS Galaxy Survey
1300 Mpc
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Power Spectrum of density fluctuations
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Power spectrum of density fluctuations
Bias b2(k)Pg(k)/Pm(k)
Non-linearity
2dFGRS
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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

Neutrino Free Streaming
n
F
b, cdm
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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
• HDM ruled out by structure formation
  CDM

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Neutrinos as Hot Dark Matter
Massive Neutrinos can still be subdominant DM
limits on m? from Structure Formation

• Effect of Massive Neutrinos suppression of
  Power at small scales

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Effect of massive neutrinos on the CMB and Matter
Power Spectra
Max Tegmark www.hep.upenn.edu/max/
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NEUTRINO MASS BOUNDS FROM COSMOLOGY
Relic neutrinos
Effect of neutrino mass on cosmological
observables
Current bounds and future sensitivities
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Cosmological bounds on neutrino mass(es)
A unique cosmological bound on m? DOES NOT exist !

• Different analyses have found upper bounds on
  neutrino masses, but they depend on
• The assumed cosmological model number of
  parameters (problem of parameter degeneracies)
• The combination of cosmological data used

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Cosmological Parameters example
SDSS Coll, PRD 69 (2004) 103501
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Cosmological Data

• CMB Temperature WMAP plus data from other
  experiments at large multipoles (CBI,ACBAR,VSA)
• CMB Polarization WMAP
• Large Scale Structure
• Galaxy Clustering (2dF,SDSS)
• Bias (Galaxy, ) Amplitude of the Matter P(k)
  (SDSS,s8)
• Lyman-a forest independent measurement of
  power on small scales
• Priors on parameters from other data SNIa (Om),
  HST (h),

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Absolute mass scale searches
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Neutrino masses in 3-neutrino schemes
From present evidences of atmospheric and solar
neutrino oscillations
eV
solar
atm
atm
solar
3 degenerate massive neutrinos Sm? 3m0
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Neutrino masses in 3-neutrino schemes
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Bound on m? after first year WMAP data
3 degenerate massive neutrinos
Sm? lt 0.7 eV O?h2 lt 0.0076
More conservative Sm? lt 1.01 eV Including
also SDSS Sm? lt 0.75 eV
Hannestad JCAP 0305 (2003) 004 Elgarøy Lahav
JCAP 0305 (2003) 004
95 CL
m0 lt 0.23 eV
Barger et al, PLB 595 (2004) 55
WMAPCBIACBAR2dFGRSs8Lyman a Spergel et al
ApJ. Suppl.148 (2003) 175
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Cosmological bounds on neutrino mass since 2003
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Neutrino masses in 3-neutrino schemes
Currently disfavored
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Global analysis ? oscillations tritium ?
decay 0?2? Cosmology
Fogli et al., PRD 70 (2004) 113003
CMB 2dF
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The bound depends on the number of neutrinos

• Example in the 31 scenario, there are 4
  neutrinos (including thermalized sterile)
• Calculate the bounds with N? gt 3

Abazajian 2002, di Bari 2002
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Sm? and Neff degeneracy
(0 eV,3)
(0 eV,7)
(2.25 eV,7)
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Analysis with Sm? and Neff free
WMAP ACBAR SDSS 2dF
Previous priors (HST SN-Ia)
2s upper bound on Sm? (eV)
Hannestad Raffelt, JCAP 0404 (2004) 008 Crotty,
Lesgourgues SP, PRD 69 (2004) 123007
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Non-thermal relic neutrinos
? The spectrum could be distorted after neutrino
decoupling Example decay of a light scalar
after BBN

• CMB LSS data still compatible with large
  deviations from a thermal neutrino spectrum
  (degeneracy NT distortion Neff)
• Better expectations for future CMB LSS data,
  but model degeneracy NT- Neff remains

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Future sensitivities to Sm?

• Next CMB data from WMAP and PLANCK (other CMB
  experiments on large ls) temperature and
  polarization spectra
• SDSS galaxy survey 106 galaxies (250,000 for
  2dF)
• Forecast analysis in WMAP and O?0 models

Hu et al, PRL 80 (1998) 5255
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Analysis of future bounds on Sm?

• Forecast analysis calculating the Fisher matrix
  Fij

CMB part
Galaxy Survey part
Veff effective volume of the galaxy survey
Estimator of the error on parameter ?i
Fiducial cosmological model (Obh2 , Omh2 , h ,
ns , t, Sm? ) (0.0245 , 0.148 , 0.70 , 0.98 ,
0.12, Sm? )
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PLANCKSDSS
Ideal CMB40xSDSS
Lesgourgues, SP Perotto, PRD 70 (2004) 045016
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Analysis of future sensitivities on Sm? summary
Sm detectable at 2s if larger than
0.21 eV (PLANCKSDSS) 0.13 eV
(CMBpolSDSS) 0.07 eV (ideal40xSDSS)
measure absolute ? mass scale !!!
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Future sensitivities to Sm? new ideas
galaxy weak lensing and CMB lensing
no bias uncertainty small scales in linear regime
makes CMB sensitive to much smaller masses
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Future sensitivities to Sm? new ideas
galaxy weak lensing and CMB lensing
sensitivity of future weak lensing
survey (4000º)2 to m? s(m?) 0.1 eV Abazajian
Dodelson PRL 91 (2003) 041301
sensitivity of CMB (primary lensing) to
m? s(m?) 0.15 eV (Planck) s(m?) 0.04 eV
(CMBpol) Kaplinghat, Knox Song PRL 91 (2003)
241301
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Conclusions
Cosmological observables efficiently constrain
some properties of (relic) neutrinos
?
Bounds on the sum of neutrino masses from CMB
2dFGRS or SDSS, and other cosmological data (best
Sm?lt0.42 eV, conservative Sm?lt1 eV)
Sub-eV sensitivity in the next future (0.1-0.2 eV
and better) ? Test degenerate mass region and
eventually the IH case
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FINE