Cosmological aspects of neutrinos (III)

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Cosmological aspects of neutrinos (III)
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• Sergio Pastor (IFIC Valencia)
• JIGSAW 2007
• TIFR Mumbai, February 2007

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Cosmological aspects of neutrinos
3rd lecture
keV sterile neutrinos as Dark Matter
Bounds on m? from CMB, LSS and other data
Bounds on the radiation content (Neff)
Future sensitivities on m? from cosmology
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Neutrino oscillations in the Early Universe
Neutrino oscillations are effective when medium
effects get small enough
Compare oscillation term with effective potentials
Coupled neutrinos
Oscillation term prop. to ?m2/2E
Second order matter effects prop. to GF(E/MZ2
)?(e-)?(e)
First order matter effects prop.
to GFn(e-)-n(e)
Strumia Vissani, hep-ph/0606054
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keV sterile neutrinos mixed with active species
Consider 2? active-sterile mixing with ??m2 of
order keV2 and very small mixing angle
Probability of conversion in the primordial
plasma (active neutrinos still interacting)
?oscoscillation length ?sscattering length
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keV states created in partial equilibrium with
the right DM density Would behave as
Warm Dark Matter lower limits from Structure
Formation See e.g. Viel et al 2006
Dodelson Widrow 1994 Shi Fuller
1999 Abazajian et al 2001 Dolgov Hansen 2002

Kusenko, Neutrino 2006
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Bounds on m? from CMB, LSS and other data
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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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Neutrinos as Hot Dark Matter
Massive Neutrinos can still be subdominant DM
limits on m? from Structure Formation (combined
with other cosmological data)
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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 WMAP3
Dependence on the data set used. An example
Fogli et al., hep-ph/0608060
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Neutrino masses in 3-neutrino schemes
CMB galaxy clustering
Lesgourgues SP, Phys. Rep. 429 (2006) 307
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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
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Extra relativistic particles

• 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 on Neff from BBN and from CMBLSS
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Effect of Neff at later epochs

• Neff modifies the radiation content
• Changes the epoch of matter-radiation equivalence

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CMBLSS allowed ranges for Neff

• Set of parameters ( Obh2 , Ocdmh2 , h , ns , A
  , b , Neff )
• DATA WMAP other CMB LSS HST ( SN-Ia)
• Flat Models
• Non-flat Models
• Recent result

Hannestad Raffelt, astro-ph/0607101
95 CL
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Allowed ranges for Neff
Using cosmological data (95 CL)
Mangano et al, astro-ph/0612150
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Future bounds on Neff

• Next CMB data from WMAP and PLANCK (other CMB
  experiments on large ls) temperature and
  polarization spectra
• Forecast analysis in O?0 models

Lopez et al, PRL 82 (1999) 3952
PLANCK
WMAP
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Future bounds on Neff
Updated analysis Larger errors
?Neff 3 (WMAP) ?Neff 0.2 (Planck)
Bowen et al 2002
Bashinsky Seljak 2003
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The bound on Sm? 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
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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, JCAP 0611 (2006) 016
Crotty, Lesgourgues SP, PRD 69 (2004) 123007
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Parameter degeneracy Neutrino mass and w
In cosmological models with more parameters the
neutrino mass bounds can be relaxed. Ex
quintessence-like dark energy with ?DEw pDE
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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)

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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?
Future cosmological data will be available from
CMB (Temperature Polarization anis.) Galaxy
redshift surveys Galaxy cluster surveys Weak
lensing surveys CMB lensing
WMAP, SPT, ACT, BICEP, QUaD, BRAIN, ClOVER,
PLANCK, SAMPAN, Inflation Probe, SDSS, SDSS-II,
ALHAMBRA, KAOS, DES, CFHTLS, SNAP, LSST,
Pan-STARRS, DUO
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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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End of 3rd lecture