Study of nonlocality effects in direct capture reactions with Lagrange-mesh $R$-matrix method

Abstract: We apply the Lagrange-mesh $R$-matrix method to calculate the $S$-factor for the $^{13}$C$(p,\gamma)^{14}$N and $^{16}$O$(p,\gamma)^{17}$F direct radiative capture reactions. By comparing the astrophysical $S$-factors calculated with nonlocal and local potentials, we investigate the nonlocality effects coming from the nuclear potentials in the direct capture reactions. Our calculations are in good agreement with the experimental data and indicate a nonnegligible difference in the results of local and nonlocal potentials. The use of small diffuseness narrow potentials also provides a remarkably good fit in the case with multiple broad resonances. Our findings suggest that the nonlocal potential improves the calculated results although the difference between the local and nonlocal potentials is smaller than uncertainties from other sources. We propose the nonlocality potential should be used in the potential model calculation of future astrophysics rates evaluation.