On the Synthesis of Elements at Very High Temperatures

Wagoner, Robert V.; Fowler, William A.; Hoyle, F.

doi:10.1086/149126

Cited by 807 publications

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“…In contrast, BBN occurs at sufficiently high temperatures (T ∼ 10 9 K) that this is not a serious problem, and data are generally present at exactly the energies where they are needed for a BBN abundance calculation without any recourse to theoretical modeling. In fact, there is a sufficiently large body of precise data in the energy range needed for BBN that the results of the calculation have remained nearly the same since the standard code was first run by Wagoner in 1967 [6], despite a slow trickle of new cross section measurements. Nonetheless, some uncertainty remains in the calculations, arising from experimental uncertainties in determining these cross sections.…”

Section: Introductionmentioning

confidence: 99%

Estimating reaction rates and uncertainties for primordial nucleosynthesis

2000

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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

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Section: Introductionmentioning

confidence: 99%

Estimating reaction rates and uncertainties for primordial nucleosynthesis

2000

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“…Finally, the total 7 Be(n,γα) cross section is reported in Fig.3 (dashed line), deduced by combining the experimental data with the calculated relative DRC contributions. In the same figure is reported the cross section from the evaluated nuclear data by Wagoner [6] (brown curve). These data included the contribution from the positive-parity states with even angular momentum above the neutron separation threshold.…”

Section: Resultsmentioning

confidence: 99%

The Cosmological Lithium Problem and the Measurement of the ⁷Be(n, α) Reaction at n_TOF-CERN

Musumarra¹,

Barbagallo²

2017

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

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A possible explanation of the so-called "Cosmological Lithium Problem", an important unsolved problem in Nuclear Astrophysics, involves large systematic uncertainties in the cross-sections of reactions leading to the destruction of 7 Be during the Big-Bang Nucleosynthesis (BBN). Among these reactions, the 7 Be(n,) is the most uncertain. So far, only a single measurement with thermal neutrons has been performed. Therefore, BBN calculations had to rely on rather uncertain theoretical extrapolations. The short half-life of 7 Be (53.29 d) and the low cross section have prevented, up to now, to obtain experimental data at keV neutron energies typical for BBN studies. We have measured for the first time at n_TOF the 7 Be(n,) reaction in a wide neutron energy range, from thermal up to 10 keV. This measurement has been performed, at the new beam line (EAR2) of the Neutron-Time-Of-Flight facility n_TOF at CERN. The two -particles, emitted back-to-back in the reaction, have been detected by mean of sandwiches of silicon detectors and, by exploiting the coincidence technique, we were able to suppress the large  and n-induced background. The 7 Be isotope production and purification has been performed by PSI-Zurich Switzerland.

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“…In their pioneer studies, Peebles (1966) and Wagoner et al (1967) demonstrated that D, 3 He and 4 He could well have been produced in solar-system abundances in the 'primordial fireball'.…”

Section: Introductionmentioning

confidence: 99%

Galactic evolution of D, ³He and ⁴He

Romano

2009

Proc. IAU

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Abstract. The uncertainties which still plague our understanding of the evolution of the light nuclides D, 3 He and 4 He in the Galaxy are described. Measurements of the local abundance of deuterium range over a factor of 3. The observed dispersion can be reconciled with the predictions on deuterium evolution from standard Galactic chemical evolution models, if the true local abundance of deuterium proves to be high, but not too high, and lower observed values are due to depletion onto dust grains. The nearly constancy of the 3 He abundance with both time and position within the Galaxy implies a negligible production of this element in stars, at variance with predictions from standard stellar models which, however, do agree with the (few) measurements of 3 He in planetary nebulae. Thermohaline mixing, inhibited by magnetic fields in a small fraction of low-mass stars, could in principle explain the complexity of the overall scenario. However, complete grids of stellar yields taking this mechanism into account are not available for use in chemical evolution models yet. Much effort has been devoted to unravel the origin of the extreme helium-rich stars which seem to inhabit the most massive Galactic globular clusters. Yet, the issue of 4 He evolution is far from being fully settled even in the disc of the Milky Way.

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On the Synthesis of Elements at Very High Temperatures

Cited by 807 publications

References 0 publications

Estimating reaction rates and uncertainties for primordial nucleosynthesis

Estimating reaction rates and uncertainties for primordial nucleosynthesis

The Cosmological Lithium Problem and the Measurement of the ⁷Be(n, α) Reaction at n_TOF-CERN

Galactic evolution of D, ³He and ⁴He

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On the Synthesis of Elements at Very High Temperatures

Cited by 807 publications

References 0 publications

Estimating reaction rates and uncertainties for primordial nucleosynthesis

Estimating reaction rates and uncertainties for primordial nucleosynthesis

The Cosmological Lithium Problem and the Measurement of the 7Be(n, α) Reaction at n_TOF-CERN

Galactic evolution of D, 3He and 4He

Contact Info

Product

Resources

About

The Cosmological Lithium Problem and the Measurement of the ⁷Be(n, α) Reaction at n_TOF-CERN

Galactic evolution of D, ³He and ⁴He