The puzzling origin of the 6Li plateau

We discuss the 6Li abundance evolution within a hierarchical model of Galaxy formation which correctly reproduces the [Fe/H] distribution of metal-poor halo stars. Contrary to previous findings, we find that neither the level (6Li/H=6x10^-12) nor the flatness of the 6Li distribution with [Fe/H] can be reproduced under the most favourable conditions by any model in which 6Li production is tied to a (data-constrained) Galactic star formation rate via cosmic ray spallation. Thus, the origin of the plateau might be due to some other early mechanism unrelated to star formation.