1202.5232 (C. Broggini et al.)

The cosmological 7Li problem from a nuclear physics perspective    [PDF]

C. Broggini, L. Canton, G. Fiorentini, F. L. Villante

The primordial abundance of 7Li 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 7Li abundance produced by arbitrary (temperature dependent)
modifications of the nuclear reaction rates. Then, considering that 7Li is
mainly produced from 7Be via the electron capture process 7Be + e^- \to 7Li +
\nu_e, we assess the impact of the various channels of 7Be 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 parameter space for a
nuclear physics solution of the 7Li problem is considerably reduced. We exclude
that resonant destruction in the channels 7Be + t and 7Be + 3He can explain the
7Li puzzle. Resonances in 7Be + d and 7Be + alpha could potentially produce
relevant effects but very favorable conditions are required. For the 7Be +
alpha channel, the possibility of a (partially) suitable resonant level in 11C
is studied in the framework of a coupled-channel model.

View original: http://arxiv.org/abs/1202.5232