Big Bang Nucleosynthesis

Richard H. CyburtJINA@MSU

Heavy ElementNucleosynthesis

s-processr-processp-process

NSEIron

Group

HydroStaticNucl.

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

Cosmology

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)

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

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: 1206.2239