Big Bang Nucleosynthesis

Report
Richard H. Cyburt
[email protected]
Hydro NSE
Static Iron
Nucl. Group
Heavy Element
Nucleosynthesis
s-process
r-process
p-process

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

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
First published in Weltall and Menschheit (1907) edited by Hans Kraemer

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)

General Relativity
◦ theory of gravity

Standard Model of Particle Physics
◦ Constituents of normal matter
◦ Interactions between them
Dark Side of
Cosmology
◦ Dark Matter
◦ Dark Energy
Courtesy of George Lucas

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

If the universe is expanding….
◦ What was it like in the past?
•Smaller
•Hotter
•Denser
◦ What happens to its constituents?
 Baryons- n, p, nuclides

At kT>1 MeV
◦ Thermal equilibrium
◦ Chemical equilibrium
◦ Main constitients




} NSE
Photons
Neutrinos
Electrons/positrons
Small number of baryons (n & p)
n/p = exp(-Dm/T)

Dynamical timescale
◦ Hubble expansion rate H ~ T2/MP

Reaction timescales
◦ Weak interaction GW ~ T5/MW4
◦ Rxn rates Grxn ~ rBlrxn

When T~1 MeV
◦ GW~H weak rates become slow
 n’s stop interacting
◦ Electrons/positrons become NR
 e+ + e2g
 energy goes into all but n’s
 Tg > Tn


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

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.



Light Element
Abundances
Agreemen
t
He: known syst.
4
Olive & Skillman 2004
D: few obs. systems

Burles, Kirkman, O’Meara
He: extrap. error
3
Disagreemen
t
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

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)
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) 105005
7Be(d,pa)4He
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)


S27 100 old value
Coc et al (2004)

New expt performed
Angulo et al (2005)

No impact on BBN

What about a missing
resonance?
Rule out renorm >99%
(Cyburt & Pospelov arXiv: 0906.4373)

Not strong enough!!!
Kirseborn & Davids PRC 84 (2011) 058801
O’Malley et al PRC 84 (2011) 042801
Non-thermal processes
(Voronchev, Nakao, Tsukida, & Nakamura
PRD 85 (2012) 067301)

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:1205.4000)
and electron screening affects on BBN
(PRC83 (2011) 018801

Obs syst errors larger or depletion?

Some evidence of Li depletion
◦
6,7Li(p,a)
(Masseron et al arXiv: 1203.3295)
(Lind et al. arXiv: 1001.5153)
rxns deplete Li
 Pre-MS stars
(Molaro et al. arXiv: 1206.1298, Yee and Jensen ApJ 711 (2010 303
& 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!



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)

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: 1206.2239

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