Dortmund 2021 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 13: Cosmic Rays I
T 13.9: Vortrag
Montag, 15. März 2021, 18:05–18:20, Tm
Measurement of the ultrahigh-energy cosmic-ray composition using a Markov Chain Monte Carlo approach — •Olena Tkachenko for the Pierre Auger collaboration — Institute for Astroparticle Physics, Karlsruhe Institute of Technology, Germany
To understand the nature and to constrain the possible astrophysical sources of ultrahigh-energy cosmic rays (UHECRs) the determination of the mass composition is essential. One of the most sensitive observables to the cosmic-ray mass composition is the depth of atmospheric shower maximum, Xmax. The fractions of different mass groups can be estimated by comparing the Xmax distributions, as measured by the Fluorescence Detector of the Pierre Auger Observatory, to the predictions obtained from air shower simulations.
In this talk we present an estimate of the mass composition from the Xmax distribution with the Markov Chain Monte Carlo methods (MCMC). We test the performance of the algorithm on the simulated data with different benchmark mass composition scenarios and study the statistical properties of the outcome. Furthermore, we fit real data from the Pierre Auger Observatory and compare the estimated fractions with the previous results. The most important advantage of the MCMC mass composition analysis is the possibility to sample from the posterior distribution of the composition fractions. We will present the example applications like the average rigidity of cosmic rays as a function of energy.