Linear discriminant analysis for particle separation using the SD-750 array and AMIGA UMD

I. D. VERGARA QUISPE; P. M. HANSEN; J. ALVAREZ MUÑIZ; D. MELO

PUBLICACION INTERNA DE LA COLABORACION INTERNACIONAL AUGER

Pierre Auger Observatory

Año: 2022

2250-835X

AMIGA (Auger Muons and Infill for the Ground Array) is the upgrade of the Pierre Auger Observatory consisting of an array of surface water-Cherenkov detectors at 750 m distance (SD-750), accompanied by buried scintillator detectors used for muon counting (UMD). AMIGA is designed to lower the energy threshold for full efficiency by one order of magnitude with respect to that of the regular SD-1500 array (from 10**18.5 eV - to 10**17.5 eV). In this note the discrimination power of several observables sensitive to primary mass, and accessible to SD-750 and UMD, is studied. The separation power between primary proton, iron and photon-induced showers is explored. The observables are combined in a linear discriminant multivariate analysis and its discrimination power is evaluated. It is shown that the observables that reflect the mounic component of the showers are very good to discriminate between proton and photon primaries, when samples of particles at the same energy are compared. However, when trying to discriminate primary protons with lower energy than the primary photons to account for a possible bias in energy, their discrimination power decreases. We have found that a combination of muonic observables with the average Area-over-Peak of the event ⟨AoP⟩, allows a good separation when discriminating primaries with different energies.