Compilation and R-matrix analysis of Big Bang nuclear reaction rates

Descouvemont, Pierre; Adahchour, Abderrahim; Angulo, C.; Coc, A.; Vangioni‐Flam, Elisabeth

doi:10.1016/j.adt.2004.08.001

Cited by 313 publications

(421 citation statements)

References 79 publications

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“…Refs. [63,64]). The uncertainties quoted in Tables VIII, IX, and X of Appendix A approximate a 1σ (∼68.3 percent) confidence level for a multiple parameter fit.…”

Section: A Parameter Uncertainties and Correlationsmentioning

confidence: 99%

R-matrix analysis of16O compound nucleus reactions

et al. 2013

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Background Over the last 60 years, a large amount of experimental nuclear data has been obtained for reactions which probe the 16 O compound nucleus near the alpha and proton separation energies, the energy regimes most important for nuclear astrophysics. Difficulties and inconsistencies in R-matrix fits of the individual reactions prompt a more complete analysis.Purpose Determine the level of consistency between the wide variety of experimental data using a multiple entrance/exit channel R-matrix framework. Using a consistent set of data from multiple reaction channels, attain an improved fitting for the 15 N(p, γ0) 16 O reaction data.Methods Reaction data for all available reaction channels were fit simultaneous using a multichannel R-matrix code.Results Over the wide range of experimental data considered, a high level of consistency was found, resulting in a single consistent R-matrix fit which described the broad level structure of 16 O below Ex = 13.5 MeV. The resulting fit was used to extract an improved determination of the low energy S-factor for the reactions 15 N(p, γ) 16 O and 15 N(p, α) 12 C. ConclusionThe feasibility and advantages of a complete multiple entrance/exit channel R-matrix description for the broad level structure of 16 O has been achieved. A future publication will investigate the possible effects of the multiple channel analysis on the reaction 12 C(α, γ) 16 O.

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“…Refs. [63,64]). The uncertainties quoted in Tables VIII, IX, and X of Appendix A approximate a 1σ (∼68.3 percent) confidence level for a multiple parameter fit.…”

Section: A Parameter Uncertainties and Correlationsmentioning

confidence: 99%

R-matrix analysis of16O compound nucleus reactions

et al. 2013

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“…The most recent Planck result [4] for the baryon density, Ω B h 2 = 0.02226 ± 0.00016, corresponds to a baryon-to-photon ratio of η = (6.10 ± 0.04) × 10 −10 . Because the uncertainty in η is now less than 1%, standard big bang nucleosynthesis (SBBN) [5][6][7] is a parameter-free theory [8], and relatively precise predictions of the primordial abundances of the light elements D, 3 He, 4 He, and 7 Li are available [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. While the 7 Li abundance remains problematic [17], recent D/H determinations from quasar absorption systems have become quite precise, in their own right, and they are in excellent agreement with the prediction from SBBN and the CMB [23].…”

Section: Introductionmentioning

confidence: 99%

The effects of He I λ10830 on helium abundance determinations

Aver

Olive

Skillman

2015

J. Cosmol. Astropart. Phys.

428

489

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Abstract. Observations of helium and hydrogen emission lines from metal-poor extragalactic H II regions, combined with estimates of metallicity, provide an independent method for determining the primordial helium abundance, Y p . Traditionally, the emission lines employed are in the visible wavelength range, and the number of suitable lines is limited. Furthermore, when using these lines, large systematic uncertainties in helium abundance determinations arise due to the degeneracy of physical parameters, such as temperature and density. Recently, Izotov, Thuan, & Guseva (2014) have pioneered adding the He I λ10830 infrared emission line in helium abundance determinations. The strong electron density dependence of He I λ10830 makes it ideal for better constraining density, potentially breaking the degeneracy with temperature. We revisit our analysis of the dataset published by Izotov, Thuan, & Stasińska (2007) and incorporate the newly available observations of He I λ10830 by scaling them using the observed-to-theoretical Paschen-gamma ratio. The solutions are better constrained, in particular for electron density, temperature, and the neutral hydrogen fraction, improving the model fit to data, with the result that more spectra now pass screening for quality and reliability, in addition to a standard 95% confidence level cut. Furthermore, the addition of He I λ10830 decreases the uncertainty on the helium abundance for all galaxies, with reductions in the uncertainty ranging from 10-80%. Overall, we find a reduction in the uncertainty on Y p by over 50%. From a regression to zero metallicity, we determine Y p = 0.2449 ± 0.0040, consistent with the BBN result, Y p = 0.2470 ± 0.0002, based on the Planck determination of the baryon density. The dramatic improvement in the uncertainty from incorporating He I λ10830 strongly supports the case for simultaneous (thus not requiring scaling) observations of visible and infrared helium emission line spectra.

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“…2 (normalized to the Marcucci et al (2005) theoretical S -factor). It shows that previous fits [27][28][29] were driven down by the scarce data at BBN energies. This is not the case anymore when the theoretical energy dependence of Marcucci et al (2005) is assumed.…”

Section: LI and D Nucleosynthesismentioning

confidence: 91%

“…2. Ratio of experimental [22][23][24][25], fitted [5,[27][28][29] and new theoretical [30] S -factors to the theoretical one [20]; the horizontal lines correspond to the theoretical S -factor scaled by α ± ∆α [5]. (Systematic uncertainties in the range 4.5-9% are not shown.…”

Section: LI and D Nucleosynthesismentioning

confidence: 99%

Primordial Nucleosynthesis

Coc

2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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Primordial or big bang nucleosynthesis (BBN) is now a parameter free theory whose predictions are in good overall agreement with observations. However, the 7 Li calculated abundance is significantly higher than the one deduced from spectroscopic observations. Most solutions to this lithium problem involve a source of extra neutrons that inevitably leads to an increase of the deuterium abundance. This seems now to be excluded by recent deuterium observations that have drastically reduced the uncertainty on D/H and also calls for improved precision on thermonuclear reaction rates.

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Compilation and R-matrix analysis of Big Bang nuclear reaction rates

Cited by 313 publications

References 79 publications

R-matrix analysis of16O compound nucleus reactions

R-matrix analysis of16O compound nucleus reactions

The effects of He I λ10830 on helium abundance determinations

Primordial Nucleosynthesis

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