Pop III Hypernova Nucleosynthesis and Abundances in Very Metal-Poor Halo Stars

We calculate evolution and nucleosynthesis in massive Pop III stars with M = 13 ~ 270Msun, and compare the results with abundances of very metal-poor halo stars. The observed abundances can be explained by the energetic core-collapse supernovae with M < ~ 130Msun (``hypernovae'') but not by pair-instability supernovae (PISNe) with M ~ 140-270 Msun. This result constrain the IMF for the Pop III and very metal-poor Pop II stars.