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Description
Various detectors at Pierre Auger Observatory observe the extensive air showers using different observation techniques. The most reliable technique for studying the composition is the fluorescence technique, which observes the longitudinal development of the charged component of an atmospheric air shower. Any difference in composition will be visible in the cross-section of the interactions with atmospheric nuclei and is observed in the measurements of the different average depths of the maximum development of the electromagnetic component in the atmosphere (Xmax) for different nuclei, as well as in the different statistical dispersion of the Xmax distributions (∆Xmax).
Rather than using the Xmax observable directly for mass composition analysis, we examined the correlation between Xmax and another observable dependent on the primary mass measured from the Underground Muon Detectors. Using a correlation parameter minimizes the effect of the muon deficit and reduces the dependency on the high-energy hadronic interaction model used in the analysis.
In this work, we define a new observable (Tb) based on the muon density measured by the Underground Muon Detectors and a correlation coefficient r (Xmax, Tb). The capability of the correlation coefficient to distinguish between mixed and pure compositions is then studied from simulations of the showers and the detectors. The dependence of the correlation coefficient on the high-energy interaction model was also investigated.
