The Cosmological Energy Density of Neutrinos from Oscillation Measurements

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The Cosmological Energy Density of Neutrinos from
Oscillation Measurements

• Kev Abazajian
• Fermilab

June 10, 2003
NuFact 03 Fifth International Workshop on
Neutrino Factories Superbeams
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WMAP Measurement of 10-5 fluctuations on the
entire sky to 0.25
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The photon last scattering surface
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Primordial Soup of Neutrinos, etc.

• Number density from thermodynamic equilibrium

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Big Bang Nucleosynthesis ?concordance of light
element abundances with standard theory
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Neutrino energy density beyond the standard model
(assumption)

• Neutrino Asymmetry
• Extra Neutrino Flavors ns, ns, ns
• Models 22, 31, 32, 3N

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BBN From a baryometer to a calorimeter
The primordial He abundance Yp 0.238 0.002
0.005 (Olive, Steigman Skillman 1997 Fields
Olive 1998) Yp 0.244 0.002 (Izotov
Thuan 1998)
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Degenerate Big Bang Nucleosynthesis
Using the observed abundances of D, 4He, and 7Li
alone, BBN is very pliable to allow large
neutrino asymmetries Due to cancelling effects
between nm/t and ne, and baryon density, Wbh2
BBN Allowed
BBN Allowed
Orito et al 02 astro-ph/0203352
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Evolution of Neutrino Asymmetries in the Early
Universe
Thermal Potential (finite temperature effects)
Vacuum Oscillation
e/- / m/- background
Neutrino Self-Potential
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Transformation of neutrino asymmetries
number density of neutrinos
Generally

• LMA solar maximal ATM
• ?Any chemical potential will alter the 4He
  abundance.
• x ltlt1

Dolgov et al.
(Dolgov et al, hep-ph/0201287 Abazajian,
Beacom, Bell astro-ph/0203442 Wong
hep-ph/0203180 )
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Neutrino Flavor Momentum Synchronization
Abazajian, Beacom Bell astro-ph/0203442
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The Synchronized Magnetic Dipole of Neutrino
Flavor
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The Death of Degenerate BBN and New Constraints
Allowed
Allowed
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LMA Solar, q12
Atmospheric, q23
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The cosmological neutrino density from qsol
(Maltoni)
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(No Transcript)
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Non-zero q13 gt 10-10
Normal Hierarchy
Inverted Hierarchy
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Light Sterile Neutrinos
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4-Neutrino Mass-modelling
Maltoni, Schwetz, Valle 2001, 2002 Päs, Song
Weiler 2002
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Constraining Sterile Neutrino Mixing

• Collisions decohere neutrino gas and populate
  sterile neutrinos
• Requiring that ns are not equilibrated (Nnlt4)

The relevant amplitude is simply
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Original 2-neutrino limitsLangacker
1989Barbieri Dolgov 1990Enqvist,
Kainulainen, Thomson 1992Shi, Schramm Fields
1993
Application to all 4 neutrino modelsK.
Abazajian, Astropart. Phys., astro-ph/0205238
P. Di Bari, PRD 65, 043509 (2002)
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31
Indirect nm -gt ne
Along with unitarity, forces large amplitude
mixing with large dm2, violating BBN bound
K. Abazajian, Astropart. Phys., astro-ph/0205238
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Both solar (SNO) neutral current signal of D
breakup and capture and atmospheric (Super-K)
enhanced neutral current component and matter
effects experiments are now effectively
appearance experiments, and disfavor large
sterile components Sterile must be split between
upper and lower doublet
K. Abazajian, Astropart. Phys., astro-ph/0205238
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• Assuming Standard Big Bang Nucleosynthesis
• Something more precise than optimistic and
  pessimistic limits
• And using only
• The Baryon Density? from the deuterium
  abundanceD/H (3.0 0.4) x 10-5Wbh2 0.020
  0.002 (95 CL)(Burles, Nollet Turner 2000
  Burles Tytler 1998)? from the CMBWbh2
  0.022(0.004)(-0.003)(DASIDMR) (BOOMerANG)
• The primordial helium abundanceYp 0.241
  0.002 0.006 (Olive, Steigman Skillman 1997
  Fields Olive 1998)(Izotov Thuan 1998)

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Constraint Evasion New Physics

• Pre-existing lepton number (L 105 B)
• A fifth mass eigenstate, mostly sterilemay
  dynamically generate lepton number (Foot, Thomson
  Volkas, 1996) sufficiently early
• Generation of majoron fields (Berezinsky Bento
  2001)
• Low reheating temperature (3 active neutrinos are
  not thermalized)
• Baryon-Antibaryon inhomogeneities Nn lt 7
  (Giovannini, Kurki-Suonio Sihvola 2002)
• Extended quintessence (dark radiation) (Chen,
  Scherrer Steigman 2001)
• CPT violating Neutrinos (Murayama Yanagida
  2001 Barenboim, Borrisov, Lykken Smirnov 2001)

n5
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The MiniBooNE Experiment
see Ion Stancus talk (next)
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Summary

• Future measurements of qLMA and q13 will further
  constrain the cosmological neutrino density
• Big bang nucleosynthesis and the CMB (in the
  future) is
• Best probe of relic neutrino asymmetries
• And has consequences for four neutrino models, or
  vice-versa