Demonstrating the (d,p) Reaction as a Surrogate for (n,γ)

Neutron-capture reactions are important to stellar nucleosynthesis and for societal applications. However, direct measurements of the (n,γ) reaction cross section on these exotic nuclei are very challenging or impossible. The difficulty in directly determining the (n,γ) reaction cross section has motivated the development of several indirect techniques for constraining it, one of which is the Surrogate Reactions Method. This method indirectly determines the ^AZ(n,γ)^A+1Z cross section by measuring the decay of the compound nucleus formed in the X(a,c)^A+1Z reaction. However, the accuracy of previous attempts to extracting an (n,γ) cross section from surrogate measurements have been limited by their inability to account for differences in the entry spin distribution between the surrogate and desired reactions. The (d,p) reaction is a promising candidate for an (n,γ) surrogate reaction from a theoretical and an experimental perspective. Recently, a new description of the d+A reaction has been developed [1] which enables the determination of the entry spin-parity distribution of the compound nucleus formed in a (d,p) reaction as a function of excitation energy. This description of the (d,p) reaction was used with a new method for constraining the parameters of a Hauser-Feshbach calculation through fits to experimental data [2]. The method has been used to describe the ⁹⁵Mo(n,γ) reaction; the extracted cross sections are in excellent agreement with data. I will summarize these efforts and show results.

 [1] G. Potel, F. M. Nunes, and I. J. Thompson Phys. Rev. C 92, 034611 (2015)

[2]  J. E. Escher et al. EPJ Web of Conf. 122, 12001 (2016)

[3] A.R. De L. Musgrove, B. Allen, J. Boldeman, and R. Macklin Nucl. Phys. A 270, 108 (1976)