TY - JOUR
T1 - An update on the big bang nucleosynthesis prediction for 7Li
T2 - The problem worsens
AU - Cyburt, Richard H.
AU - Fields, Brian D.
AU - Olive, Keith A.
PY - 2008
Y1 - 2008
N2 - The lithium problem arises from the significant discrepancy between the primordial 7Li abundance as predicted by big bang nucleosynthesis (BBN) theory and the Wilkinson Microwave Anisotropy Probe (WMAP) baryon density, and the pre-Galactic lithium abundance inferred from observations of metal-poor (Population II) stars. This problem has loomed for the past decade, with a persistent discrepancy of a factor of 2-3 in 7Li/H. Recent developments have sharpened all aspects of the Li problem. Namely: (1)BBN theory predictions have sharpened due to new nuclear data; in particular, the uncertainty on the reaction rate for3He(α,γ) 7Be has reduced to 7.4%, nearly a factor of 2 tighter than previous determinations. (2)The WMAP five-year data set now yields a cosmic baryon density with an uncertainty reduced to 2.7%. (3)Observations of metal-poor stars have tested for systematic effects. With these, we now find that the BBN+WMAP predicts7Li/H = (5.24-0.67+0.71) × 10-10. The central value represents an increase by 23%, most of which is due to the upward shift in the3He(α,γ)7Be rate. More significant is the reduction in the7Li/H uncertainty by almost a factor of 2, tracking the reduction in the3He(α, γ)7Be error bar. These changes exacerbate the Li problem; the discrepancy is now a factor 2.4 or 4.2σ (from globular cluster stars) to 4.3 or 5.3σ (from halo field stars). Possible resolutions to the lithium problem are briefly reviewed, and key experimental and astronomical measurements highlighted.
AB - The lithium problem arises from the significant discrepancy between the primordial 7Li abundance as predicted by big bang nucleosynthesis (BBN) theory and the Wilkinson Microwave Anisotropy Probe (WMAP) baryon density, and the pre-Galactic lithium abundance inferred from observations of metal-poor (Population II) stars. This problem has loomed for the past decade, with a persistent discrepancy of a factor of 2-3 in 7Li/H. Recent developments have sharpened all aspects of the Li problem. Namely: (1)BBN theory predictions have sharpened due to new nuclear data; in particular, the uncertainty on the reaction rate for3He(α,γ) 7Be has reduced to 7.4%, nearly a factor of 2 tighter than previous determinations. (2)The WMAP five-year data set now yields a cosmic baryon density with an uncertainty reduced to 2.7%. (3)Observations of metal-poor stars have tested for systematic effects. With these, we now find that the BBN+WMAP predicts7Li/H = (5.24-0.67+0.71) × 10-10. The central value represents an increase by 23%, most of which is due to the upward shift in the3He(α,γ)7Be rate. More significant is the reduction in the7Li/H uncertainty by almost a factor of 2, tracking the reduction in the3He(α, γ)7Be error bar. These changes exacerbate the Li problem; the discrepancy is now a factor 2.4 or 4.2σ (from globular cluster stars) to 4.3 or 5.3σ (from halo field stars). Possible resolutions to the lithium problem are briefly reviewed, and key experimental and astronomical measurements highlighted.
KW - Big bang nucleosynthesis
KW - Dark matter
KW - Pshysics of the early universe
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U2 - 10.1088/1475-7516/2008/11/012
DO - 10.1088/1475-7516/2008/11/012
M3 - Article
AN - SCOPUS:66249125007
VL - 2008
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 11
M1 - 012
ER -