Temperature-resolved sensitivities of 56 Ni production to helium-burning reactions in pair-instability supernovae

We propose a temperature-resolved Monte Carlo (MC) approach to identify the temperature regimes in which low-energy helium-burning reaction rates most strongly affect nucleosynthesis in very massive stars that undergo pair-instability supernovae (PISNe). By performing MC simulations of PISNe, we quantify how temperature-dependent variations in key helium-burning reaction rates, i.e., the triple- α and 12 C (α,γ) 16 O rates, influence 56 Ni synthesis. Thousands of stellar evolution calculations using MESA reveal that both the 12 C (α,γ) 16 O and triple- α reactions exhibit their strongest sensitivity at T 2.5 times 10 8, K, but with opposite correlation signs. We show that this temperature corresponds to the regime in which the ratio of the sampled rate multipliers is most clearly imprinted on the pre-carbon-burning C/O composition. This demonstrates that PISN nucleosynthesis can probe helium-burning reaction rates in specific low-temperature regimes.