Direct Measurement of Resonances in 7Be (α ,γ )11C Relevant to ν p -Process Nucleosynthesis

We have performed the first direct measurement of two resonances of the ⁷Be (α ,γ )¹¹C reaction with unknown strengths using an intense radioactive ⁷Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of 1.73 ±0.25 (stat )±0.40 (syst ) eV and 125_-25⁺²⁷(stat )±15 (syst ) meV , respectively. The present results have reduced the uncertainty in the ⁷Be (α ,γ )¹¹C reaction rate to ∼9.4 %- 10.7 % over T =1.5 - 3 GK , which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae (ν p process). We find no effect of the new, constrained reaction rate on ν p -process nucleosynthesis.