The cosmological {sup 7}Li problem from a nuclear physics perspective
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Padova, Via Marzolo 8, Padova I-35131 (Italy)
- Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (LNL), Viale dell'Università 2, Legnaro I-35020 (Italy)
The primordial abundance of {sup 7}Li as predicted by Big Bang Nucleosynthesis (BBN) is more than a factor 2 larger than what has been observed in metal-poor halo stars. Herein, we analyze the possibility that this discrepancy originates from incorrect assumptions about the nuclear reaction cross sections relevant for BBN. To do this, we introduce an efficient method to calculate the changes in the {sup 7}Li abundance produced by arbitrary (temperature dependent) modifications of the nuclear reaction rates. Then, considering that {sup 7}Li is mainly produced from {sup 7}Be via the electron capture process {sup 7}Be+e{sup −} → {sup 7}Li+ν{sub e}, we assess the impact of the various channels of {sup 7}Be destruction. Differently from previous analysis, we consider the role of unknown resonances by using a complete formalism which takes into account the effect of Coulomb and centrifugal barrier penetration and that does not rely on the use of the narrow-resonance approximation. As a result of this, the possibility of a nuclear physics solution to the {sup 7}Li problem is significantly suppressed. Given the present experimental and theoretical constraints, it is unlikely that the {sup 7}Be+n destruction rate is underestimated by the 2.5 factor required to solve the problem. We exclude, moreover, that resonant destruction in the channels {sup 7}Be+t and {sup 7}Be+{sup 3}He can explain the {sup 7}Li puzzle. New unknown resonances in {sup 7}Be+d and {sup 7}Be+α could potentially produce significant effects. Recent experimental results have ruled out such a possibility for {sup 7}Be+d. On the other hand, for the {sup 7}Be+α channel very favorable conditions are required. The possible existence of a partially suitable resonant level in {sup 11}C is studied in the framework of a coupled-channel model and the possibility of a direct measurement is considered.
- OSTI ID:
- 22280014
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2012, Issue 06; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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