Ca40(α,γ)Ti44 reaction in the energy regime of supernova nucleosynthesis

The Ti44(t1/2=59yr) nuclide, an important signature of supernova nucleosynthesis, has recently been observed as live radioactivity by γ-ray astronomy from the Cas A remnant. We investigate in the laboratory the major Ti44 production reaction Ca40(α,γ)Ti44 (Ec.m.∼0.6-1.2MeV/u) by direct off-line counting of Ti44 nuclei. The yield, significantly higher than inferred from previous experiments, is analyzed in terms of a statistical model using microscopic nuclear inputs. The associated stellar rate has important astrophysical consequences, increasing the calculated supernova Ti44 yield by a factor ∼2 over previous estimates and bringing it closer to Cas A observations.