Abstract and subjects
The observation of secondary gamma-rays provides an alternative method of measuring cross sections that populate excited final states in nuclear reactions. The angular distributions of these gamma-rays also provide information on the underlying reaction mechanism. Despite the large number of data of this type in the literature, publicly available R-matrix codes do not have the ability to calculate these types of angular distributions. In this paper, the mathematical formalism derived by C. R. Brune and R. J. deBoer [Phys. Rev. C 102, 024628 (2020)] is implemented in the R-matrix code AZURE2 and calculations are compared with previous data from the literature for the N-15(p, alpha(1 gamma))C-12* reaction. In addition, new measurements, made at the University of Notre Dame Nuclear Science Laboratory using the Hybrid Array of Gamma Ray Detectors (HAGRiD), are reported that span the energy range from E-p = 0.88 MeV to E-p = 4.0 MeV. Excellent agreement between the data and the phenomenological fit is obtained up to the limit of the previous fit at E-p = 2.0 MeV and the R-matrix fit is extended from E-x approximate to 13.5MeVup to E-x approximate to 15.3MeV, where N-15+p and C-12+alpha reactions are fit simultaneously for the first time. An excellent reproduction of the N-15(p, alpha(1)gamma)C-12* and C-12(alpha, alpha)C-12 data is achieved, but inconsistencies and difficulty in fitting other data are encountered and discussed.