richard h. cyburt jina@msu. heavy element nucleosynthesis s-process r-process p-process nse iron...
TRANSCRIPT
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
How do we explain obs.?
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
Information for any nucleosynthesis calculation
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)
Tenets of Modern Cosmology
General Relativity◦ theory of gravity
Standard Model of Particle Physics◦ Constituents of normal matter◦ Interactions between them
Tenets of Modern Cosmology
Tenets of Modern Cosmology
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
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
Working back to the big bang
• Denser
• Hotter
• Smaller
At kT>1 MeV◦ Thermal equilibrium◦ Chemical equilibrium◦ Main constitients
Photons Neutrinos Electrons/positrons Small number of baryons (n & p)
Initial Conditions
} NSE
n/p = exp(-Dm/T)
Dynamical timescale◦ Hubble expansion rate H ~ T2/MP
Reaction timescales◦ Weak interaction GW ~ T5/MW
4
◦ Rxn rates Grxn ~ rBlrxn
Relevant timescales
When T~1 MeV◦ GW~H weak rates become slow
n’s stop interacting◦ Electrons/positrons become NR
e+ + e- 2g energy goes into all but n’s
Tg > Tn
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
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.
Big bang nucleosynthesis
Light Element Abundances 4He: known syst.Olive & Skillman 2004
D: few obs. systems
Burles, Kirkman, O’Meara
3He: extrap. errorBania 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
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)
How to Fix Discordance
Nuke fixes: Missing Reactions?
Coc et al. ApJ 744 (2012) 158Boyd et al PRD 82 (2010) 105005
Doesn’t significantly alter the final abundance
predictions!!!!
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!!!
Nuke fixes: Mistaken Reactions?
(Cyburt & Pospelov arXiv: 0906.4373)
Kirseborn & Davids PRC 84 (2011) 058801O’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
Other Nuke 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: 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!
Astrophysical fixes
(Masseron et al arXiv: 1203.3295)(Lind et al. arXiv: 1001.5153)
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)
New Physics