the cosmological energy density of neutrinos from oscillation measurements kev abazajian fermilab...
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The Cosmological Energy Density of Neutrinos from Oscillation
MeasurementsKev 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
ee
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Number density from thermodynamic equilibrium:
Primordial Soup of Neutrinos, etc.
baryonnn
nNn
Tn
10
3
332
10
cm34011
3
cm410)3(2
ee
2eV8.93 h
mnm i
crit
ii
0.003 < m < 0.15
Neutrino Dark Matter:
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Big Bang Nucleosynthesis
►concordance of light element abundances with standard theory
WMAP
►Consistency with baryon density at 300,000 years later, at CMB decoupling
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Neutrino energy density beyond the standard model (assumption)
1. Neutrino Asymmetry:
2. Extra Neutrino Flavors: s, s’, s’’ …
Models: 2+2, 3+1, 3+2, 3+N …
1)/exp(
1),(
Tppf
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3.4 3.2 3.0
BBNBBN: From a baryometerbaryometer to a calorimetercalorimeter
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)
Gives precision measurement of the energy density of the universe at ~ 1 sec!
Constrains new neutrino physics
nNn
11
3
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BBN Allowed
BBN Allowed
Orito et al ’02astro-ph/0203352
CMB
CMB
Allowed
Using the observed
abundances of D, 4He,
and 7Li alone,
BBN is very pliable to
allow large neutrino
asymmetries
Due to cancelling
effects
between and e, and
baryon
density, bh2
“Degenerate” Big Bang Nucleosynthesis
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Vacuum Oscillation
e+/- / +/- background
Thermal Potential
(finite temperature effects)
Neutrino Self-Potential
Evolution of Neutrino Asymmetries in the Early Universe
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)(cm113
)()3(2
11
3
23
23
2
Fn
FTn
LMA solar + maximal ATM
Any chemical potential will alter the 4He abundance.
<<1
Generally:
13 flavorcm113
n
number density of neutrinos
(Dolgov et al, hep-ph/0201287 ; Abazajian, Beacom, Bell astro-ph/0203442 ; Wong hep-ph/0203180 )
Transformation of neutrino asymmetries
Dolgov et al.
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Neutrino Flavor Momentum Synchronization…
Abazajian, Beacom & Bellastro-ph/0203442
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The Synchronized “Magnetic” Dipole of Neutrino Flavor
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Allowed
Allowed
The Death of Degenerate BBN and New Constraints…
CMB
Allowed
Allowed: B
BN + LMA+Atm
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Atmospheric, 23
LMA Solar, 12
13
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The cosmological neutrino density from sol
(Maltoni)
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Non-zero: 13 > 10-10
m2atm
m2sol1
2
3
Normal Hierarchy
Inverted Hierarchy
m2atm
m2sol
1
2
3
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Light Sterile Neutrinos
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4-Neutrino Mass-modelling
Maltoni, Schwetz, & Valle 2001, 2002; Päs, Song & Weiler 2002
“3+1”
m2atm
m2sol
m2LSND
1
2
3
4
“2+2”
m2sol
m2atm
m2LSND
4
3
1
2
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Constraining Sterile Neutrino Mixing
• Collisions decohere neutrino gas and populate sterile neutrinos
• Requiring that s are not equilibrated (N<4)
The relevant amplitude is simply:
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Application to all 4 neutrino models:K. Abazajian, Astropart. Phys., astro-ph/0205238; P. Di Bari, PRD 65, 043509 (2002)
Original 2-neutrino limits:Langacker 1989;Barbieri & Dolgov 1990;Enqvist, Kainulainen, Thomson 1992;Shi, Schramm & Fields 1993
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3+1
Indirect -> e
Along with unitarity, forces large amplitude mixing with large m2, violating BBN bound
“3+1”
m2atm
m2sol
m2LSND
1
2
3
4
K. Abazajian, Astropart. Phys., astro-ph/0205238
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2+2
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
“2+2”
m2sol
m2atm
m2LSND
4
3
1
2
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:
1. The Baryon Density:● from the deuterium abundance:D/H = (3.0 ± 0.4) x 10-5
bh2 = 0.020 ± 0.002 (95% CL)(Burles, Nollet & Turner 2000; Burles & Tytler 1998)● from the CMB:bh2 = 0.022(+0.004)(-0.003)(DASI+DMR) + (BOOMerANG)
2. The primordial helium abundance:Yp = 0.241± 0.002 ± 0.006 (Olive, Steigman & Skillman 1997; Fields & Olive 1998)(Izotov & Thuan 1998)
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Constraint Evasion & New Physics
1. Pre-existing lepton number (L ~ 105 B)2. A fifth mass eigenstate, mostly sterile
may dynamically generate lepton number (Foot, Thomson & Volkas, 1996) sufficiently early
3. Generation of majoron fields (Berezinsky & Bento 2001)4. Low reheating temperature (3 active neutrinos are not
thermalized)5. Baryon-Antibaryon inhomogeneities: N < 7 (Giovannini, Kurki-
Suonio & Sihvola 2002)6. Extended quintessence (“dark radiation”) (Chen, Scherrer &
Steigman 2001)7. CPT violating Neutrinos (Murayama & Yanagida 2001; Barenboim,
Borrisov, Lykken & Smirnov 2001)
5
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The MiniBooNE Experiment… see Ion Stancu’s talk (next)
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Summary…Summary…
• Future measurements of LMA and 13 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