A systematic approach to Covariance matrix formulation in charged particle activation experiments

TL;DR

This paper develops a detailed covariance and correlation matrix analysis method for cross section measurements in charged particle activation experiments, emphasizing the importance of correlated uncertainties.

Contribution

It introduces a formalism for explicitly calculating and propagating covariance matrices, including systematic and statistical uncertainties, in activation cross section data.

Findings

Covariance matrices reveal interdependencies among experimental parameters.

Systematic uncertainties significantly impact the total uncertainty estimation.

The formalism improves the reliability of data interpretation and comparison.

Abstract

This work presents a detailed covariance and correlation matrix analysis for experimentally measured cross sections obtained using the activation technique. Both statistical and systematic contributions to the covariance matrix were explicitly calculated using sensitivity coefficients. The detector efficiency was determined by refitting standard source data with an exponential function, and the associated covariance matrix of the fitted parameters was propagated to estimate the uncertainty in efficiency at the relevant $\gamma$-ray energy. The cross sections and the corresponding experimental parameters, such as beam flux, target thickness, $\gamma$-ray intensity, and decay corrections, were taken from previously published measurements and are used here for the purpose of illustrating the covariance formalism. The resulting covariance and correlation matrices provide a comprehensive representation of uncertainties and their interdependencies. This formalism demonstrates the importance of including correlated uncertainties for reliable interpretation and comparison of experimental cross section data.