Theoretical uncertainty of(α,n)reactions relevant for the nucleosynthesis of lightr-processnuclei in neutrino-driven winds

Abstract

Background: Neutrino-driven winds following core-collapse supernova explosions have been proposed as a possible site where light r-process nuclei (between Fe and Ag) might be synthesized. In these events, (α, n) reactions are key to move matter towards the region of higher proton number. Abundance network calculations are very sensitive to the rates for this type of reactions.Purpose: The present work aims at evaluating the theoretical uncertainty of these (α, n) reactions calculated with reaction codes based on the Hauser-Feshbach model.Method: We compared several (α,n) rates taken from TALYS and the NON-SMOKER database to determine the uncertainties due to the existing technical differences between both codes. In addition, we evaluated the sensitivity of TALYS rates to variations in the alpha optical potentials, masses, level densities, optical potentials, pre-equilibrium intranuclear transition rates, level structure, radiative transmission coefficients, and width-fluctuation correction factors.Results: The main source of uncertainty at low temperatures are mostly due to the use of different alpha optical potentials. Differences between TALYS and NON-SMOKER at high temperatures arise from the energy binning algorithm used by each code. We have also noticed that the (α,n) rates from the NON-SMOKER database correspond to the inclusive reaction, instead of the exclusive (α,1n) channel calculated in the present work and used in network calculations.Conclusions: Theoretical uncertainties in calculated reaction rates can be as high as 1-to-2 orders of magnitude, and strongly dependent on the temperature of the environment. Besides direct measurements of the inclusive and exclusive (α, 1n) reaction rates, experimental studies of alpha optical potentials are crucial to improve the performance of reaction codes.

Determination of the Mg36(n,γ)Mg37 reaction rate from Coulomb dissociation of Shubhchintak1, Chatterjee2, Shyam3 2017Phys. Rev. C

“…Nevertheless, we use these estimates because they are easy to obtain and their uncertainties are not larger than the differences seen between and (n, γ) and (α, n) reaction rates in Fig. 7 [34].…”

α scattering and α -induced reaction cross sections of Zn64 at low energies

“…Interestingly, in the A ≈ 20-50 mass range, experimental (α,p) and (α,n) data are well described using the McFadden-Satchler potential [26]. Several alternative suggestions for low-energy α-nucleus potentials have been made in the past years [9,19,20,[27][28][29][30][31], and the related uncertainties of α-induced reaction cross sections at low energies were studied very recently [32][33][34].…”

Nuclear processes in astrophysics: Recent progress

“…So far modelers have to rely on theoretical predictions of those rates. Furthermore, the theoretical uncertainties of the calculated reaction rates can be as high as 2 orders of magnitude and abundance network calculations are highly sensitive within the expected theoretical uncertainties of these rates [235]. A recent systematic study searching for the critical reaction rates that influence most of the final abundances in weak r-process scenarios has permitted the identification of the most important reaction rates, which can then be pinned down experimentally by measurements in radioactive beam facilities [236].…”