Big Bang Nucleosynthesis
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Transcript Big Bang Nucleosynthesis
Richard H. Cyburt
JINA@MSU
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