# Projection of Good Quantum Numbers for Reaction Fragments

## TL;DR

This paper introduces a particle projection technique for reaction fragments that simplifies calculations of conserved quantities like particle number and angular momentum, avoiding complex Pfaffian evaluations.

## Contribution

It presents a new particle projection method applicable to reaction fragments, extending to angular momentum and particle projected energy distributions, simplifying previous computational approaches.

## Key findings

- Efficient particle projection technique avoiding Pfaffians.
- Extension to angular momentum and energy distributions.
- Framework for simultaneous particle and angular momentum projection.

## Abstract

In reactions the wave packets of the emerging products typically are not eigenstates of particle number operators or any other conserved quantities and their properties are entangled. I describe a particle projection technique in parts of space, which eschews the need to evaluate Pfaffians in the case of overlap of generalized Slater determinants or Hartree-Fock-Bogoliubov type of vacua. The extension of these formulas for calculating either angular momentum or particle projected energy distributions of the reaction fragments are presented as well. The generalization to simultaneous particle and angular momentum projection of various reaction fragment observables is straightforward.