1. NEUTRINOS AND BBN ( & THE CMB) Gary Steigman
(with thanks to J. P. Kneller & V. Simha)
Departments of Physics and Astronomy
Center for Cosmology and Astro-Particle Physics
Ohio State University
NO – VE, Venice, Italy, April , 2008

2. Primordial Nucleosynthesis Relic Photons (CMB) are free
~ 100 s after the Big Bang
Primordial Nucleosynthesis
~ 0.1 s after the Big Bang
Neutrinos Decouple
~ 400 kyr after the Big Bang
Relic Photons (CMB) are free

3. BBN (~ 20 Minutes) , The CMB (~ 400 kyr) &
LSS (~ 10 Gyr) Provide Complementary Probes
Of The Early Evolution Of The Universe
Do predictions and observations of the baryon
density (B) and the expansion rate (H) of the
Universe agree at these different epochs?
(G. S., Ann. Rev. Nucl. Part. Sci., 57 (2007) 463)
V. Simha & G. S. astro-ph/

4.  tBBN  4  24 min. The Early, Hot, Dense Universe
Is A Cosmic Nuclear Reactor
As the Universe expands and cools, BBN
“begins” at T  70 keV (when n / p  1 / 7)
Coulomb barriers and the absence of
free neutrons terminate BBN at T  30 keV
 tBBN  4  24 min.

5. Baryon Density Parameter B  nN / n ; 10   B = 274 Bh2
Note : Baryons  Nucleons
B  nN / n ; 10   B = Bh2
where : B  B / c ; c  critical density
Hubble parameter : h  H0 / 100 km s-1 Mpc-1
h  0.7 ; H0-1 = 9.8 / h  14 Gyr

6. Evolution of Deuterium
10
More nucleons  less D

7. DEUTERIUM --- The Baryometer Of Choice
As the Universe evolves, D is only DESTROYED 
* Anywhere, Anytime : (D/H) t  (D/H) P
* For Z << Z : (D/H) t  (D/H) P (Deuterium Plateau)
(D/H) P is sensitive to the baryon density (    )
H  and D  are seen in Absorption, BUT …
* H  and D  spectra are identical  H  Interlopers?
* Unresolved velocity structure  Errors in N(H ) ?

8. D/H vs. Metallicity Low – Z / High – z QSOALS Deuterium Plateau ?
Real variations,
systematic differences,
statistical uncertainties ?

9. D/H vs. Metallicity For Primordial D/H adopt the mean
For the D/H error adopt the
dispersion around the mean
105(D/H)P = 2.68 ± 0.27

10. D /H + SBBN  10 = ± 0.4
SBBN

11. YP depends VERY WEAKLY on the nucleon abundance
Almost all neutrons are incorporated in 4He
n / p  1 / 7  YP  0.25 P
10
YP  4He Mass Fraction
YP does depend on the competition between Γwk & H

12. The Expansion Rate (H  Hubble Parameter)
provides a probe of Non-Standard Physics
S2  (H/ H)2  /  N / 43
S is parameterized by N
   + N  and N  3 + N
NOTE : G/ G  S2  N / 43
4He is sensitive to H while D probes B

13. Extragalactic 4He Observations (H  Regions)
As O/H  0, Y  0
SBBN Prediction : YP =
YP = ± ( Or : YP < @ 2 σ )

14. BBN (D, 4He)  For N ≈ 2.4 ± 0.4 D & 4He Isoabundance Contours
YP & yD  105 (D/H)
4.0
3.0
2.0
0.25
0.24
0.23
D & 4He Isoabundance Contours
Kneller & Steigman (2004)

15. N vs. 10 From BBN (D & 4He) ( YP < 0.255 @ 2 σ )
BBN Constrains N
N < 4
N > 1
V. Simha & G.S.

16. Lithium Observations in Galactic Halo Stars
[Li]  12 + log(Li/H)
Asplund et al.
Ryan, Norris, Beers
Lithium Plateau (?)

17. BBN and Primordial (Pop ) Lithium
Li too low ?
[Li]  12 + log(Li/H)  2.6 – 2.7
[Li]  12 + log(Li/H)  2.1
to be continued …

18. Even for N  3 Y + D  H  Li  H  4.0  0.7 x 10 10
yLi  1010 (Li/H)
4.0
3.0
2.0
0.25
4.0
0.24
0.23
Li depleted / diluted
in Pop  stars ?
Kneller & Steigman (2004)

19. CBR

20. 10 = 4.5, 6.1, 7.5 CMB Temperature Anisotropy Spectrum
(T2 vs. ) Depends On The Baryon Density
 
10 = 4.5, 6.1, 7.5
V. Simha & G.S.
The CMB is an early - Universe Baryometer

21. CMB  10 = ± 0.2
10 Likelihood
CMB

22. SBBN (20 min) & CMB (380 kyr) AGREE !
10 Likelihoods
CMB
SBBN

23. CMB Temperature Anisotropy Spectrum
Depends on the Radiation Density R (S or N)
 
N = 1, 3, 5
V. Simha & G.S.
The CMB is an early - Universe Chronometer

24. CMB + LSS + HST Prior on H0 N vs. 10 CMB + LSS Constrains 10
V. Simha & G.S.

25. BBN (D & 4He) & CMB AGREE !
N vs. 10
CMB
BBN
V. Simha & G.S.

26.   Use the CMB + LSS to bound η10 and N
Use BBN to predict YP , yDP , yLiP (solid black)
Compare to the observed abundances (dashed)   ?
V. Simha & G.S.

27. Some consequences of the good agreement between BBN and the CMB
Entropy Conservation : N (CMB) / N (BBN) = ± 0.07
Modified Radiation Density (late decay of massive particle)
ρRCMB / ρRBBN =
Variation in the Gravitational Constant ?
GBBN / G0 = ± 0.07 ; GCMB / G0 = ± 0.12

28. BBN + CMB Combined Fit N vs. 10 ( YP < 0.255 @ 2 σ )
V. Simha & G.S.

29. e Degeneracy (Non – Zero Lepton Number)
Alternative to N  3 (S  1)
e Degeneracy (Non – Zero Lepton Number)
For e = e/kT  0 (more e than anti - e)
n/p  exp ( m/kT  e )  n/p   YP 
YP probes Lepton Asymmetry
The CMB is insensitive to e

30. e Degeneracy (Non – Zero Lepton Number)
For N = 3 :
e = 
YP & yD  105 (D/H)
4.0
4.0
3.0
2.0
&
10 =  0.4 
0.23
0.24
0.25
But, [Li] =  0.7
Still !
Li depleted / diluted
in Pop  stars ?

31. For BOTH N & e Free (using BBN + CMB)
V. Simha & G.S.

32. For BOTH N & e Free (using BBN + CMB)
V. Simha & G.S.

33. (The Theorist’s Mantra) More & Better Data Are Needed !
SUCCESS
BBN (D, 3He, 4He) & the CMB Agree !
(Lithium ?)
CHALLENGE
(The Theorist’s Mantra)
More & Better Data Are Needed !

35. BBN & The CMB Provide Complementary Probes Of The Early Universe
Do predictions and observations
of the baryon density agree at
20 minutes and at kyr ?
(Ann. Rev. Nucl. Part. Sci., 57 (2007) 463)

36. D, 3He, 7Li are potential BARYOMETERS
BBN – Predicted Primordial Abundances
4He Mass Fraction
BBN Abundances of D, 3He, 7Li
are RATE (DENSITY) LIMITED
7Li
7Be
D, 3He, 7Li are potential BARYOMETERS

37. Two pathways to mass - 7
10

38. SBBN 10 Likelihoods from D and 4He
AGREE ?
to be continued …

39. Summary : Baryon Density Determinations
Depleted ?
D & 3He agree with the CMB
N < 3 ?

40. Observational Uncertainties Or New Physics?
Depleted ?
N < 3 ?