Experimental measurement of C12+O16 fusion at stellar energies

Abstract

The total cross section of the $^{12}\mathrm{C}+^{16}\mathrm{O}$ fusion reaction has been measured at low energies to investigate the role of this reaction during late stellar evolution burning phases. A high-intensity oxygen beam, produced by the 5 MV pelletron accelerator at the University of Notre Dame, impinged on a thick, ultrapure graphite target. Protons and $\ensuremath{\gamma}$ rays were simultaneously measured in the center-of-mass energy range from 3.64 to 5.01 MeV for singles and from 3.73 to 4.84 MeV for coincidence events, using silicon and Ge detectors. Statistical model calculations were employed to interpret the experimental results. The emergence of a new resonance-like broad structure and a decreasing trend in the $S$-factor data towards lower energies (opposite to previous data) are found for the $^{12}\mathrm{C}+^{16}\mathrm{O}$ fusion reaction. Based on these results the uncertainty range of the reaction rate within the temperature range of late stellar burning environments is discussed.