Precision cosmology and neutrinos

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Precision cosmology and neutrinos
?

• Sergio Pastor (IFIC)
• NOW 2006
• Conca Specchiulla, September 2006

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Precision cosmology and neutrinos

• Sergio Pastor (IFIC)
• NOW 2006
• Conca Specchiulla, September 2006

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Outline
Introduction the Cosmic Neutrino Background
Precision cosmology and neutrinos
Relic Neutrinos as DM
Effect of neutrino masses on cosmological
observables
Current bounds and future sensitivities
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This is a neutrino!
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Neutrinos coupled by weak interactions(in
equilibrium)
Primordial Nucleosynthesis
TMeV tsec
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Neutrinos coupled by weak interactions(in
equilibrium)
Free-streaming neutrinos (decoupled) Cosmic
Neutrino Background
Neutrinos keep the energy spectrum of a
relativistic fermion with eq form
TMeV tsec
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Relativistic neutrinos
TeV
At least 2 species are NR today

• Neutrino cosmology is interesting because Relic
  neutrinos are very abundant
• The CNB contributes to radiation at early times
  and to matter at late times (info on the number
  of neutrinos and their masses)
• Cosmological observables can be used to test
  non-standard neutrino properties

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The Cosmic Neutrino Background

• Number density
• Energy density

Massless
Massive m?gtgtT
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Evolution of the background densities 1 MeV ? now
Oi ?i/?crit
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Possible values of the neutrino masses
Data on flavour oscillations do not fix the
absolute scale of neutrino masses
eV
NORMAL
INVERTED
atm
solar
What is the value of m0 ?
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Absolute mass scale searches
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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 are very large
• 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 (combined
with other cosmological data)
Talks by Ø. Elgarøy and M. Viel
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Power Spectrum of density fluctuations
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Neutrinos as Hot Dark Matter effect on P(k)
Massive Neutrinos can still be subdominant DM
limits on m? from Structure Formation (combined
with other cosmological data)

• Effect of Massive Neutrinos suppression of
  Power at small scales

f?
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Structure formation after equality
baryon and CDM experience gravitational clustering
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Structure formation after equality
baryon and CDM experience gravitational clustering
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Structure formation after equality
baryon and CDM experience gravitational clustering
growth of dr/r (k,t) fixed by gravity vs.
expansion balance ? dr/r ? a
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Structure formation after equality
baryon and CDM experience gravitational clustering
neutrinos experience free-streaming with v c
or ltpgt/m
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Structure formation after equality
baryon and CDM experience gravitational clustering
baryon and CDM experience gravitational clustering
neutrinos experience free-streaming with v c
or ltpgt/m
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Structure formation after equality
baryon and CDM experience gravitational clustering
baryon and CDM experience gravitational clustering
neutrinos experience free-streaming with v c
or ltpgt/m
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Structure formation after equality
baryon and CDM experience gravitational clustering
baryon and CDM experience gravitational clustering
neutrinos experience free-streaming with v c
or ltpgt/m

• neutrinos cannot cluster below a diffusion
  length
• l ? v dt lt ? c dt

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Effect of massive neutrinos on P(k)
Observable signature of the total mass on P(k)
P(k) massive P(k) massless
various f?
Lesgourgues SP, Phys. Rep. 429 (2006)
307
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DATA on CMB temperature /polarization anisotropies
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Effect of massive neutrinos on the CMB spectra

• Direct effect of sub-eV massive neutrinos on the
  evolution of the baryon-photon coupling is very
  small
• Impact on CMB spectra is indirect non-zero O?
  today implies a change in the spatial curvature
  or other Oi . The background evolution is
  modified
• Ex in a flat universe,
• keep O?OcdmObO?1
• constant

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Effect of massive neutrinos on the CMB spectra
Problem with parameter degeneracies change
in other cosmological parameters can mimic the
effect of nu masses
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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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How to get a bound (measurement) of neutrino
masses from Cosmology
Fiducial cosmological model (Obh2 , Omh2 , h ,
ns , t, Sm? )
PARAMETER ESTIMATES
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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
• Baryon acoustic oscillations (SDSS)
• Bounds on parameters from other data SNIa (Om),
  HST (h),

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Cosmological Parameters example
SDSS Coll, PRD 69 (2004) 103501
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Cosmological bounds on neutrino mass(es)
A unique cosmological bound on m? DOES NOT exist !
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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, since they depend on
• The combination of cosmological data used
• The assumed cosmological model number of
  parameters (problem of parameter degeneracies)
• The properties of relic neutrinos

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Cosmological bounds on neutrino masses using WMAP1
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Cosmological bounds on neutrino masses using WMAP3
Fogli et al., hep-ph/0608060
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Neutrino masses in 3-neutrino schemes
CMB galaxy clustering
Fig from Strumia Vissani, NPB726(2005)294
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Tritium ? decay, 0?2? and Cosmology
Fogli et al., hep-ph/0608060
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0?2? and Cosmology
Fogli et al., hep-ph/0608060
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Relativistic particles in the Universe
At Tltme, the radiation content of the Universe
is Effective number of relativistic neutrino
species Traditional parametrization of the energy
density stored in relativistic particles
Talks by F. Villante and P. di Bari
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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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Analysis with Sm? and Neff free
WMAP ACBAR SDSS 2dF
Hannestad Raffelt, astro-ph/0607101
Crotty, Lesgourgues SP, PRD 69 (2004) 123007
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Non-standard relic neutrinos
The cosmological bounds on neutrino masses are
modified if relic neutrinos have non-standard
properties (or for non-standard models)

• Two examples where the cosmological bounds do not
  apply
• Massive neutrinos strongly coupled to a light
  scalar field they could annihilate when becoming
  NR
• Neutrinos coupled to the dark energy the DE
  density is a function of the neutrino mass
  (mass-varying neutrinos)

Talks by G. Mangano and P. Serra
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Future sensitivities to Sm?
Future cosmological data will be available from

• CMB (TP) galaxy redshift surveys
• CMB (TP) and CMB lensing
• Weak lensing surveys
• Weak lensing surveys CMB lensing

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PLANCKSDSS

• Fisher matrix analysis expected sensitivities
  assuming a fiducial cosmological model, for
  future experiments with known specifications

Fiducial cosmological model (Obh2 , Omh2 , h ,
ns , t, Sm? ) (0.0245 , 0.148 , 0.70 , 0.98 ,
0.12, Sm? )
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Future sensitivities to Sm? new ideas
weak gravitational and
CMB lensing lensing
No bias uncertainty Small scales much closer to
linear regime Tomography 3D reconstruction
Makes CMB sensitive to smaller neutrino masses
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Future sensitivities to Sm? new ideas
weak gravitational and
CMB lensing 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?) 0.044 eV
(CMBpol) Kaplinghat, Knox Song PRL 91 (2003)
241301
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CMB lensing recent analysis
s(M?) in eV for future CMB experiments alone
Lesgourgues et al, PRD 73 (2006) 045021
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Summary of future sensitivities
Lesgourgues SP, Phys. Rep. 429 (2006) 307
Future cosmic shear surveys
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Conclusions
Cosmological observables can be used to bound
(or measure) neutrino properties, in particular
the sum of neutrino masses (info complementary to
laboratory results)
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Current bounds on the sum of neutrino masses
from cosmological data (best Sm?lt0.2-0.4 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