# Two-step nuclear reactions: The Surrogate Method, the Trojan Horse Method and their common foundations

## TL;DR

This paper demonstrates that the Surrogate and Trojan Horse Methods in nuclear physics share a common theoretical foundation, the INEB theory, despite their different applications and energy regimes.

## Contribution

It reveals that both methods are unified under the INEB theory, clarifying their similarities and differences in nuclear reaction analysis.

## Key findings

- Both methods are based on the INEB theory.
- They are applicable at different energies and kinematic regions.
- The methods contain both direct and compound reaction contributions.

## Abstract

In this Letter I argue that the Surrogate Method, used to extract the fast neutron capture cross section on actinide target nuclei, which has important practical application for the next generation of breeder reactors, and the Trojan Horse Method employed to extract reactions of importance to nuclear astrophysics, have a common foundation, the Inclusive Non-Elastic Breakup (INEB)Theory. Whereas the Surrogate Method relies on the premise that the extracted neutron cross section in a (d,p) reaction is predominantly a compound nucleus one, the Trojan Horse Method, assumes a predominantly direct process for the secondary reaction induced by the surrogate fragment. In general, both methods contain both direct and compound contributions, and I show how theses seemingly distinct methods are in fact the same but at different energies and different kinematic regions. The unifying theory is the rather well developed INEB theory.