Testing spallation processes with beryllium and boron

The nucleosynthesis of Be and B by spallation processes provides unique ins ight into the origin of cosmic rays. Namely, different spallation schemes p redict sharply different trends for the growth of LiBeB abundances with res pect to oxygen. "Primary" mechanisms predict BeB proportional to O and are well motivated by the data if O/Fe is constant at low metallicity. In contr ast, "secondary" mechanisms predict BeB proportional to O-2 and are consist ent with the data if O/Fe increases toward low metallicity as some recent d ata suggest. Clearly, any primary mechanism, if operative, will dominate ea rly in the history of the Galaxy. In this paper, we fit the BeB data to a t wo-component scheme which includes both primary and secondary trends. In th is way, the data can be used to probe the period in which primary mechanism s are effective. We analyze the data using consistent stellar atmospheric p arameters based on Balmer line data and the continuum infrared flux. Result s depend sensitively on Population II O abundances (and O/Fe trends), which have recently seen renewed interest. We explore the implications of these results phenomenologically, using a systematic and consistent compilation a nd fitting of BeBOFe data. Two-component Be-O fits indicate that primary an d secondary components contribute equally at [O/H](eq) = -1.8 for Balmer li ne data; and [O/H](eq) = -1.4 to -1.8 for IRFM. We apply these constraints to recent models for LiBeB origin. The Balmer line data do not show any evi dence for primary production. On the other hand, the IRFM data do indicate a preference for a two-component model, such as a combination of standard G CR and metal-enriched particles accelerated in superbubbles. These conclusi ons rely on a detailed understanding of the abundance data including system atic effects which may alter the derived O-Fe and BeB-Fe relations.