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Description
The CNO cycle is the primary energy production mechanism in massive stars, with the $^{15}$N$(p, \gamma)^{16}$O reaction serving as a crucial branching point connecting the CN and NO cycles. The ratio of reaction rates between $^{15}$N$(p, \gamma)^{16}$O and $^{15}$N$(p,\alpha)^{12}$C directly determines the nitrogen and oxygen abundances within the CNO cycle, which in turn affect stellar evolution and nucleosynthesis. However, there is significant discrepancy in the existing low-energy experimental data for the $^{15}$N$(p, \gamma)^{16}$O reaction cross-section. This work remeasured the $^{15}$N$(p, \gamma)^{16}$O reaction using the 350 keV accelerator at INEST (the Institute of Nuclear Energy Safety Technology), in the energy range $E_p$=110-260 keV. We used the FCVA (Filter Cathodic Vacuum Arc) technology to enrich Ti$^{15}$N targets and measured the target thickness by scanning the resonance of $^{15}$N$(p, \alpha\gamma)^{12}$C at $E_{cm}$=842 keV. The 4$\pi$-BGO detector array can effectively absorb nearly all the -rays produced by the reaction. The detector is shielded and counter-coincident on the outside, which significantly reduces the measurement background. We used $\gamma$-ray summing detection techniques and Bayesian analysis method to fit the single spectra and summing spectra, yielding the $\gamma$-ray transition branching ratios and the detection efficiency of the summing peak, and further calculated the S-factor. Currently, R-matrix analysis of the $^{15}$N$(p, \gamma)^{16}$O data is in progress. In the future, we will conduct low-energy measurements of the $^{15}$N$(p, \alpha)^{12}$C direct reaction and calculate the impact of the ratio of these reaction rates on the abundances of nitrogen and oxygen in the CNO cycle.
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