Effects of triple-alpha reaction rates on the nucleosynthesis in massive stars

Ogata, Kan, and Kamimura (2009) evaluated directly nonresonant triple-alpha reaction rate by solving the Schrödinger equation of the three-body system. The scattering wave function is obtained by the continuum-discretized coupled-channels method (CDCC). The CDCC results drastically differ from previous rates at low temperature. We investigated the effect of this triple-alpha reaction rate (OKK rate) on the s-process in a massive star during the helium and carbon burnings in Kikuchi et al. (2012). In the present paper, we investigate the effects of triple-alpha and ¹²C(α,γ) ¹⁶O reaction rates on the massive star evolution and the nucleosynthesis. We calculate the massive star evolution of a 25 MO; star from helium core burning phase to the phase just before the core-collapse. We also perform a spherically symmetric hydrodynamic simulation of the supernova explosion and the nucleosynthesis to estimate the ejected elements. Though the production of s-elements depends on the combinations of the reaction rates, we roughly confirm the weak s-process that is the production of s-elements up to A = 90. We find that most s-elements produced during the stellar evolution survived even after the supernova explosion. We show that the production of p-elements depends on peak temperatures during the supernova shock propagation and p-process layers, which is affected eventually by the stellar evolution path, triple-α and ¹²C(α,γ) ¹⁶O reaction rates.