  Nonrotating, zero metallicity stars with initial masses 140 < M < 260 solar
masses are expected to end their lives as pair-production supernovae (PPSNe),
in which an electron-positron pair-production instability triggers explosive
nuclear burning. Interest in such stars has been rekindled by recent
theoretical studies that suggest primordial molecular clouds preferentially
form stars with these masses. Since metal enrichment is a local process, the
resulting PPSNe could occur over a broad range of redshifts, in pockets of
metal-free gas. Using the implicit hydrodynamics code KEPLER, we have
calculated a set of PPSN light curves that addresses the theoretical
uncertainties and allows us to assess observational strategies for finding
these objects at intermediate redshifts. The peak luminosities of typical PPSNe
are only slightly greater than those of Type Ia, but they remain bright much
longer (~ 1 year) and have hydrogen lines. Ongoing supernova searches may soon
be able to limit the contribution of these very massive stars to < 1% of the
total star formation rate density out to z=2 which already provides useful
constraints for theoretical models. The planned Joint Dark Energy Mission
satellite will be able to extend these limits out to z=6.
