Light nuclei under magnetic field and the lithium problem

Abstract

We analyze the effect of the magnetic field on the proton and neutron density distributions of the nuclei 2H, 3H, 3He, which are calculated ab initio, and the 6Li nucleus in the alpha-cluster model. It is found that the asymptotic exponential damp of the probability density at long distance is modified, and that the linear component of the exponent with respect to the magnetic field yields the leading contribution, while those of the second derivative and the confining magnetic force are subleading. Due to the linear dependence of the exponent, fluctuating magnetic fields always enhance the tunneling rate, i.e. the cross section of low energy nuclear reactions which occur at large separation across the Coulomb barrier. While this mechanism cannot suppress the production of 7Be in the early Universe, it has the potential to resolve the lithium problem either by increasing the reaction rate of 7Be + p -> 8B at the bigbang nucleosynthesis era if the magnetic field at this time was sufficiently strong, or by correcting the systematically enlarged 4He + 3He -> 7Be cross section by the unwanted magnetic field generated in the nuclear experimental setup, which was so far used as the input of the simulation of bigbang nucleosynthesis.