Cross sections for production of the 15.10 MeV and other astrophysically significant gamma-ray lines through excitation and spallation of sup 12 C and sup 16 O with protons

The ratio of the flux of 15.10-MeV gamma rays to the flux of 4.438-MeV gamma rays resulting from excitation of the corresponding states in C-12 as a sensitive measure of the spectrum of the exciting particles produced in solar flares and other cosmic sources. These gamma rays are produced predominantly by interactions with C-12 and O-16, both of which are relatively abundant in the solar photosphere. Gamma ray production cross sections for proton interactions have been reported previously for all important channels except for the production of 15.10-MeV gamma rays from O-16. The first reported measurement of the 15.10-MeV gamma ray production cross section from p + O-16 is presented here. The University of Maryland cyclotron was employed to produce 40-, 65-, and 86-MeV protons which interacted with CH2 and BeO targets. The resultant gamma ray spectra were measured with a high-purity germanium semiconductor detector at 70, 90, 110, 125, and 140 degrees relative to the direction of the incident beam for each proton energy. Other gamma ray lines resulting from direct excitation and spallation reactions with C-12 and 0-16 were observed as well, and their gamma ray production cross sections described

Realistic Calculation of the hep Astrophysical Factor

The astrophysical factor for the proton weak capture on 3He is calculated with correlated-hyperspherical-harmonics bound and continuum wave functions corresponding to a realistic Hamiltonian consisting of the Argonne v18 two-nucleon and Urbana-IX three-nucleon interactions. The nuclear weak charge and current operators have vector and axial-vector components, that include one- and many-body terms. All possible multipole transitions connecting any of the p-3He S- and P-wave channels to the 4He bound state are considered. The S-factor at a p-3He center-of-mass energy of 10 keV, close to the Gamow-peak energy, is predicted to be 10.1 10^{-20} keV b, a factor of five larger than the standard-solar-model value. The P-wave transitions are found to be important, contributing about 40 % of the calculated S-factor.Comment: 8 pages RevTex file, submitted to Phys. Rev. Let