Reaction rate sensitivity of 44Ti production in massive stars and implications of a thick target yield measurement for 40Ca(alpha,gamma)44Ti

The dynamic synergy between observation, theory, and experiment developed over many years around the field of gamma-ray astronomy has as its ultimate goal observations of specific radionuclides informing our understanding of stellar explosions and the theoretical models that predict nucleosynthesis. Observations of 56,57Ni and their decay products 56,57Co are used in many ways to constrain our current models of the core collapse mechanism. The radionuclide 44Ti (tau1/2 = 58.9 +- 0.3 yr), made in the same explosive environment but in much lower amounts compared to the very abundant nickel isotopes, is hoped to one day serve as an even more sensitive diagnostic and a valuable probe to the conditions extant in some of the deepest layers to be ejected. We [1] investigate 44Ti nucleosynthesis in adiabatic expansions from peak conditions drawn from a model for Cassiopia A and determine variations due to experimental uncertainties in two key reaction rates. We find that the current uncertainty in these two rates could lead to as large a variation in 44Ti synthesis as that produced by different treatments of stellar physics in historical models of SNII.