Na cross section near the Gamow energyγ

Carbon burning marks the ignition of the third nuclear fuel supply after H- and He-burning in the evolution of massive stars. Current estimates of carbon fusion reaction rates at astrophysical energies rely on extrapolations from higher energies. Low energy studies of ¹²C+¹²C reactions have focused either on charged particle or on γ-ray spectroscopy. Charged particle spectroscopy has the advantage that the total fusion cross section can in principle be measured, while γ-ray spectroscopy (and γ-particle coincidences) cannot account for direct transitions to the ground state of the residual nucleus and was limited at low energies due to background arising from hydrogen contamination within the target. However, the condition of being a total cross section measurement is not fulfilled in practice in the case of the particle spectroscopy due to finite energy resolution and low-energy detection limits. Recently, the Trojan Horse Method (THM) has been exploited to determine the ¹²C+¹²C cross section over the entire energy range of the Gamow window. Comparison of these results with information from newly published experiments reveal tension between THM data and direct experiments. The current status of the carbon fusion cross section and its implication will be discussed.