TITLE: The p-Nucleus Puzzle

ABSTRACT:  The origin of the intermediate and heavy elements beyond Fe has been a long-standing, important question in astronomy and astrophysics. The neutron capture s- and r-processes synthesize the bulk of those nuclei. While AGB and massive stars were found to contribute to the s-process, the site of the r-process has only recently been identified. Moreover, a number of naturally occurring, proton-rich isotopes (the p-nuclei) cannot be made in the s- and r-processes. Although their natural abundances are tiny compared to isotopes produced in neutron-capture nucleosynthesis, their  production is even more problematic. The long-time favored process, photodisintegration of material in the O/Ne-shell of a massive star during its final core-collapse supernova explosion, fails to produce the required amounts of p-nuclei in several mass ranges. Several alternative sites have been proposed but so far no conclusive evidence has been found to favor one or the other. Further important uncertainties stem from the reaction rates used in the modeling of the thermonuclear burning. This raises the interesting question whether improved nuclear physics may (fully or partially) cure the current model deficiences. Investigations in astrophysical and nuclear models, together with various "observational" information (obtained from stellar spectra, meteoritic inclusions, and nuclear experiments) comprise the pieces which have to be put together to solve the puzzle of the origin of the p-nuclei. It is an excellent example for the multifaceted, interdisciplinary approaches required to understand nucleosynthesis.