Measurement of the 14N(p,γ)15O Reaction in the CNO Cycle

During the main-sequence stage, stars generate energy through hydrogen burning: the pp chains and the CNO cycles. In stars more massive than the Sun, the density and temperature is high enough for the CNO cycles to dominate energy production over the pp chains. The main CNO cycle contributes 99% of the CNO energy pro- duction. The 14N(p, γ)15O reaction is the slowest in the cycle, thus it determines the energy production rate. It also plays an important role in the determination of the age of globular clusters.

While many experiments focused on measuring the cross section at low energies, only one comprehensive data set was available at above 0.5 MeV proton energy. Anal- ysis and calculations to these measurements showed discrepancy when extrapolating the S-factor to zero energy. In this work, the result of the cross section measurement from proton energy 0.4-3.4 MeV, as well as the angular distribution measurement from 0.7-3.6 MeV at five different angles (135◦, 90◦, 0◦, 45◦, 150◦) is presented. KN and JN Van de Graaff accelerator at the University of Notre Dame were used for the measurements.

Since measuring the cross section at astrophysical energies is not possible, R- matrix analysis was performed to extrapolate the measurements down to zero energy. This is also the first time that the angular distribution data were used for the analysis.