Absorption-Fluctuation Theorem for Nuclear Reactions: Brink-Axel, Incomplete Fusion and All That

TL;DR

This paper explores the theoretical connections between absorption, fluctuations, and various nuclear reaction cross sections, including compound nucleus, multistep, and incomplete fusion reactions, with implications for the surrogate method.

Contribution

It introduces a unified absorption-fluctuation theorem framework linking different nuclear reaction phenomena and discusses its implications for reaction modeling and the surrogate method.

Findings

Fluctuations in entrance channels lead to compound nucleus cross sections.

Intermediate channel fluctuations modify multistep reaction cross sections.

Final channel fluctuations describe incomplete fusion reactions.

Abstract

We discuss the connection between absorption, averages and fluctuations in nuclear reactions. The fluctuations in the entrance channel result in the compound nucleus, Hauser-Feshbach, cross section, the fluctuations in the intermediate channels, result in modifications of multistep reaction cross sections, while the fluctuations in the final channel result in hybrid cross sections that can be used to describe incomplete fusion reactions. We discuss the latter in details and comment on the validity of the assumptions used in the develpoment of the Surrogate method. We also discuss the theory of multistep reactions with regards to intermediate state fluctuations and the energy dependence and non-locality of the intermediate channels optical potentials.