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Big Bang Nucleosynthesis

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Presentation on theme: "Big Bang Nucleosynthesis"— Presentation transcript:

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:

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