Volume 627, July 2019
|Number of page(s)||24|
|Section||Numerical methods and codes|
|Published online||16 July 2019|
Fitting B/C cosmic-ray data in the AMS-02 era: a cookbook
Model numerical precision, data covariance matrix of errors, cross-section nuisance parameters, and mock data
LPSC, Université Grenoble Alpes, CNRS/IN2P3, 53 Avenue des Martyrs, 38026 Grenoble, France
e-mail: firstname.lastname@example.org, email@example.com
2 LAPTh, Université Savoie Mont Blanc & CNRS, 74941 Annecy Cedex, France
3 LPTHE, Sorbonne Université & CNRS, 4 Place Jussieu, 75252 Paris Cedex 05, France
4 Service de Physique Théorique, Université Libre de Bruxelles, Boulevard du Triomphe, CP225, 1050 Brussels, Belgium
Accepted: 16 June 2019
Context. AMS-02 on the International Space Station has been releasing data of unprecedented accuracy. This poses new challenges for their interpretation.
Aims. We refine the methodology to get a statistically sound determination of the cosmic-ray propagation parameters. We inspect the numerical precision of the model calculation, nuclear cross-section uncertainties, and energy correlations in data systematic errors.
Methods. We used the 1D diffusion model in USINE. Our χ2 analysis includes a covariance matrix of errors for AMS-02 systematics and nuisance parameters to account for cross-section uncertainties. Mock data were used to validate some of our choices.
Results. We show that any mis-modelling of nuclear cross-section values or the energy correlation length of the covariance matrix of errors biases the analysis. It also makes good models (χmin2/d.o.f. ≈ 1) appear as excluded (χmin2/d.o.f. ≫ 1). We provide a framework to mitigate these effects (AMS-02 data are interpreted in a companion paper).
Conclusion. New production cross-section data and the publication by the AMS-02 collaboration of a covariance matrix of errors for each data set would be an important step towards an unbiased view of cosmic-ray propagation in the Galaxy.
Key words: astroparticle physics / diffusion / methods: miscellaneous / cosmic rays
© L. Derome et al. 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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