Precision study of ground state capture in the 14N(p,gamma)15O reaction

TL;DR

This study provides a precise measurement of the 14N(p,gamma)15O reaction's ground state capture rate, reducing uncertainties critical for understanding stellar hydrogen burning in the CNO cycle.

Contribution

It offers the first high-precision measurement of ground state capture in 14N(p,gamma)15O at underground facilities, resolving previous discrepancies and uncertainties.

Findings

Discrepancy in ground state contribution resolved

Uncertainty in astrophysical S-factor significantly reduced

Ground state capture no longer dominates total S-factor uncertainty

Abstract

The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is controlled by the slowest process, 14N(p,gamma)15O, which proceeds by capture to the ground and several excited states in 15O. Previous extrapolations for the ground state contribution disagreed by a factor 2, corresponding to 15% uncertainty in the total astrophysical S-factor. At the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy, a new experiment on ground state capture has been carried out at 317.8, 334.4, and 353.3 keV center-of-mass energy. Systematic corrections have been reduced considerably with respect to previous studies by using a Clover detector and by adopting a relative analysis. The previous discrepancy has been resolved, and ground state capture no longer dominates the uncertainty of the total S-factor.