  There have been attempts to fit the abundance patterns of extremely
metal-poor stars with supernova nucleosynthesis models for the lighter elements
than Zn. On the other hand, observations have revealed that the presence of EMP
stars with peculiarly high ratio of "weak r-process elements" Sr, Y and Zr.
Although several possible processes were suggested for the origin of these
elements, the complete solution for reproducing those ratios is not found yet.
In order to reproduce the abundance patterns of such stars, we investigate a
model with neutron rich matter ejection from the inner region of the
conventional mass-cut. We find that explosive nucleosynthesis in a high energy
supernova (or "hypernova") can reproduce the high abundances of Sr, Y and Zr
but that the enhancements of Sr, Y and Zr are not achieved by nucleosynthesis
in a normal supernova. Our results imply that, if these elements are ejected
from a normal supernova, nucleosynthesis in higher entropy flow than that of
the supernova shock is required.
