High-energy breakup of 6Li as a tool to study the Big Bang nucleosynthesis reaction 2H(α,γ)6Li

Physical Review C (Impact Factor: 3.73). 11/2010; 82(6). DOI: 10.1103/PhysRevC.82.065803
Source: OAI


The recently claimed observations of non-negligible amounts of 6Li in old halo stars have renewed interest in the Big Bang nucleosynthesis (BBN) of 6Li. One important ingredient in the predicted BBN abundance of 6Li is the low-energy 2H(α,γ)6Li cross section. Up to now, the only available experimental result for this cross section showed an almost constant astrophysical S factor below 400 keV, contrary to theoretical expectations. We report on a new measurement of the 2H(α,γ)6Li reaction using the breakup of 6Li at 150 A  MeV. Even though we cannot separate experimentally the Coulomb contribution from the nuclear one, we find clear evidence for Coulomb-nuclear interference by analyzing the scattering angular distributions. This is in line with our theoretical description, which indicates a drop of the S24 factor at low energies as predicted also by most other models. Consequently, we find even lower upper limits for the calculated primordial 6Li abundance than before.

Download full-text


Available from: Naohito Iwasa
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Few-body systems provide very useful tools to solve different problems for nuclear astrophysics. This is the case of indirect techniques, developed to overcome some of the limits of direct measurements at astrophysical energies. Here the Coulomb dissociation, the asymptotic normalization coefficient and the Trojan Horse method are discussed.
    Full-text · Article · Aug 2013 · Few-Body Systems
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We identify reactions which destroy 7Be and 7Li during big bang nucleosynthesis (BBN) in the scenario of BBN catalyzed by a long-lived sub-strongly interacting massive particle (sub-SIMP or X particle). The destruction associated with non radiative X captures of the nuclei can be realized only if the interaction strength between an X particle and a nucleon is properly weaker than that between two nucleons to a degree depending on the mass of X. Binding energies of nuclei to an X particle are estimated taking the mass and the interaction strength to nuclei of the X as input parameters. Nuclear reaction rates associated with the X are estimated naively, and adopted in calculating evolutions of nuclear abundances. We suggest that the 7Li problem, which might be associated with as-yet-unrecognized particle processes operating during BBN, can be solved if the X particle interacts with nuclei strongly enough to drive 7Be destruction but not strongly enough to form a bound state with 4He of relative angular momentum L=1. Justifications of this scenario by rigorous calculations of reaction rates using quantum mechanical many-body models are highly desirable since this result involves many significant uncertainties.
    Preview · Article · Dec 2010 · Physical review D: Particles and fields
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new cosmological model of LiBeB production in the first structures has been performed. This was motivated by observations of 6Li in halo Pop II stars that indicated a potentially high abundance of this isotope, about a thousand times higher than its predicted primordial value. Using a cosmological model for the cosmic ray-induced production of this isotope in the IGM allows us to explain the observed abundance at very low metallicity. Given this constraint on the 6Li, we also calculate the non-thermal evolution with redshift of D, Be, and B in the IGM, and the resulting extragalactic gamma-ray background. The computation is performed in the framework of hierarchical structure formation considering several star formation histories including specifically Pop III stars. We find that spallative D production is negligible and that a potentially detectable Be and B plateau is produced by these processes at the time of the formation of the Galaxy (z˜3).
    Preview · Article · Jan 2011
Show more