1. Big Bang Nucleosynthesis
Richard H. Cyburt

2. Hydro
Static
Nucl.
NSE
Iron
Group
Heavy Element
Nucleosynthesis
s-process
r-process
p-process

3. How do we explain obs.? If universe ~14 Gyr old
Where’d we get so much H & He???
pp-chain is too slow
massive stars burn beyond He
Stars must have been born with that H & He
Big bang nucleosynthesis

4. Information for any nucleosynthesis calculation
What building blocks are available?
n, p, nuclides, e, g, n, etc…
What are the reaction time scales?
Related to rxn rates: t = 1/G
What are the dynamical time scales?
Hydro-static EQ; no time scale
Free-fall time t = finite

5. Cosmology
First published in Weltall and Menschheit (1907) edited by Hans Kraemer

6. Tenets of Modern Cosmology
Cosmological Principle
Universe is homogeneous
looks the same anywhere we go
Universe is isotropic
looks the same any direction we look
Laws of physics are the same everywhere(when)

7. Tenets of Modern Cosmology
General Relativity
theory of gravity
Standard Model of Particle Physics
Constituents of normal matter
Interactions between them

8. Tenets of Modern Cosmology
Dark Side of Cosmology
Dark Matter
Dark Energy
Courtesy of George Lucas

9. Working back to the big bang
GR predicts universe is expanding
Einstein tried to fix this with L
Claims its his biggest mistake
Hubble obs. recession of galaxies (1929)
First evidence for universal expansion
Subsequent obs. confirm this

10. Working back to the big bang
If the universe is expanding….
What was it like in the past?
What happens to its constituents?
Baryons- n, p, nuclides
Smaller
Hotter
Denser

12. } NSE Initial Conditions n/p = exp(-Dm/T) At kT>1 MeV
Thermal equilibrium
Chemical equilibrium
Main constitients
Photons
Neutrinos
Electrons/positrons
Small number of baryons (n & p)
} NSE
n/p = exp(-Dm/T)

13. Relevant timescales Dynamical timescale Reaction timescales
Hubble expansion rate H ~ T2/MP
Reaction timescales
Weak interaction GW ~ T5/MW4
Rxn rates Grxn ~ rBlrxn

14. Big bang nucleosynthesis
When T~1 MeV
GW~H weak rates become slow
n’s stop interacting
Electrons/positrons become NR
e+ + e g
energy goes into all but n’s
Tg > Tn

15. Big bang nucleosynthesis
n,p would like to fuse into d
But Ng(E>Bd) >> NB
So as soon as d is made, it is destroyed
So we must wait…..
Called the D bottleneck
while we wait, n’s decay

16. Big bang nucleosynthesis
T~70 keV, d not efficiently destroyed
So…….
p(n,g)d(p,g)3He(d,p)4He
We convert H into 4He (all n’s go into 4He)
Sometimes we even 3He(a,g)7Be
T~40 keV, Coulomb barrier halts nucl.

17. Light Element Abundances
4He: known syst.
Olive & Skillman 2004
D: few obs. systems
Burles, Kirkman, O’Meara
3He: extrap. error
Bania et al, Vangioni-Flam et al
7Li: add. syst.?
Spite & Spite, Ryan et al, Bonifacio et al
WMAP CMB WBh2
Bennet et al, Spergel et al
Agreement
Disagreement

19. How to Fix Discordance Obs./Exp./Thry. Systematics
(Cyburt 2004; Descouvemont et al. 2004; Serpico et al. 2004)
Nuclear Astrophys./Chemical Evolution
(Vangioni-Flam et al. 2002; Bono et al.2002; Cassisi, Salaris & Irwin 2003)
Physics beyond Standard Model
(Malaney & Mathews 1993; Sarkar 1996; Cyburt, Fields & Olive 2004)

20. Doesn’t significantly alter the final abundance predictions!!!!
Nuke fixes: Missing Reactions?
Doesn’t significantly alter the final abundance predictions!!!!
Coc et al. ApJ 744 (2012) 158
Boyd et al PRD 82 (2010)

21. Nuke fixes: Mistaken Reactions?
3He(a,g)7Be
7Li  S34
Can fix 7Li, but…
lose Solar n flux
SNO+S17+SSM=S34
(Ahmed et al, Cyburt et al, Bahcall)
Rule out renorm >99%
7Be(d,pa)4He
S27 100 old value
Coc et al (2004)
New expt performed
Angulo et al (2005)
No impact on BBN
What about a missing resonance?
Not strong enough!!!
(Cyburt & Pospelov arXiv: )
Kirseborn & Davids PRC 84 (2011)
O’Malley et al PRC 84 (2011)

22. Other Nuke fixes
Non-thermal processes (Voronchev, Nakao, Tsukida, & Nakamura PRD 85 (2012) )
d(d,n)3He, d(d,p)t, 3He(d,p)4He, t(d,n)4He
n,p from rxns are highly non-thermal
Slowed in plasma, but still partially non-thermal
Can enhance some reactions
However, thermalization is too strong at BBN T’s
Changes in abundances <1%
See also non-Maxwellian distributions (Bertulani et al arXiv: )
and electron screening affects on BBN (PRC83 (2011)

23. Astrophysical fixes Obs syst errors larger or depletion?
Some evidence of Li depletion
6,7Li(p,a) rxns deplete Li
Pre-MS stars (Molaro et al. arXiv: , Yee and Jensen ApJ 711 ( & Bildsten et al ApJ 482 (1997) 442)
MS stars (Korn et al. Nature 442 (2006) 657)
Can we deplete uniformly without increasing the observed dispersion?
Better astro models needed!
(Masseron et al arXiv: )
(Lind et al. arXiv: )

24. New Physics SUSY? Variation of fundamental constants?
Dark radiation or neutrino degeneracy?
Beyond the SM…..
SUSY?
(Cyburt, Ellis, Fields, Luo, Olive & Spanos;
Kawasaki, Kohri & Moroi;
Mathews, Kajino; Jedamzik)

25. Conclusions BBN is the first epoch of nucleosynthesis
Involves all 4 fundamental forces of nature
Standard BBN w/ CMB is parameter free
Accurately predict light element abundances
Concordance w/ 4He, 3He and D obs.
7Li remains a problem!! 6Li is not a problem!!
Steffen et al. arXiv: