Estimating reaction rates and uncertainties for primordial nucleosynthesis

Abstract

We present a Monte Carlo method for direct incorporation of nuclear inputs in primordial nucleosynthesis calculations. This method is intended to remedy shortcomings of current error estimation, by eliminating intermediate data evaluations and working directly with experimental data, allowing error estimation based solely on published experimental uncertainties. This technique also allows simple incorporation of new data and reduction of errors with the introduction of more precise data. Application of our method indicates that previous error estimates on the calculated abundances were too large by as much as a factor of three. Since uncertainties in the BBN calculation currently dominate inferences drawn from light-element abundances, the re-estimated errors have important consequences for cosmic baryon density, neutrino physics, and lithium depletion in halo stars. Our direct method allows detailed discussion of the status of the nuclear inputs, by identifying clearly the places where improved cross section measurements would be most useful. 26.35.+c, 98.80.Ft

Constraints on neutrino degeneracy from the cosmic microwave background and primordial nucleosynthesis

“…Both the BOOMERANG and DASI data sets now imply Ω b h 2 = 0.022 +0.004 −0.003 (1σ) (η 10 = 6.00 +1.10 −0.81 ). This value is close to the value implied by the cosmic deuterium abundance in high-redshift Lyman-α clouds observed along the line of sight to background quasars [40,41] Ω b h 2 = 0.020 ± 0.001 (1σ) (η 10 = 5.46 ± 0.27). Hence, the newer data imply at most a marginal requirement for a larger baryon density or neutrino degeneracy.…”

Electron screening and its effects on big-bang nucleosynthesis

“…PACS numbers: 25.40.Lw, 24.50.+g, 26.20.-f During the Big Bang the Universe evolved very rapidly and only the lightest nuclides (e.g., D, 3 He, 4 He, and 7 Li) could be synthesized. The abundances of these nuclides are probes of the conditions of the Universe during the very early stages of its evolution, i.e., the first few minutes.…”

“…Whereas v is well described by a Maxwell-Boltzmann velocity distribution for a given temperature T , the cross section σ is taken from laboratory experiments on earth, some of which are not as well known as desired [4][5][6][7][8]. The presence of atomic electrons in laboratory experiments also influence the measured values of the cross sections in a rather unexpected way (see, e.g.…”

“…Deviations from the BBN test the parameters of these models, and constrain nonstandard physics or cosmology that may alter the conditions during BBN [2,3]. Sensitivity to the several parameters and physics input in the BBN model have been investigated thoroughly in the past (see, e.g., [4][5][6][7][8][9]). In this work we consider if the screening by electrons would have any impact on the BBN predictions.…”

“…We have included all reactions of the standard BBN model using the values of the cross sections as published in Ref. [4]. The reaction rates were modified to include screening factors calculated with Eq.…”