The AMIGA underground muon detector of the Pierre Auger Observatory - performance and event reconstruction

A.M. BOTTI, THE PIERRE AUGER COLLABORATION (VER A. LUCERO EN LISTA AUTORES ARCHIVO ADJUNTO)

Wisconsin-Madison

Conferencia; 36th International Cosmic Ray Conference; 2019

University of Wisconsin-Madison, IUPAP

The Auger Muons and Infill for the Ground Array (AMIGA) aims to both lower the detection threshold of the Pierre Auger Observatory down to energies of ∼ 10^16.5 eV and to directly mea- sure the muon content of extensive air showers. AMIGA consists of an array of coupled water- Cherenkov and buried scintillation detectors deployed in two superimposed triangular grids of 433 m and 750 m spacings. Each underground detector has a total area of 30 m^2 buried at a depth of 2.3 m, to shield it from the shower electromagnetic component. The scintillation plane is seg- mented in plastic-scintillator strips with embedded wavelength-shifter optical fibers coupled to a common optical sensor. Before proceeding to the construction of the full-size array, an engineer- ing array was operated until November 2017 to validate and optimize the design, and to evaluate the performance of the detection system. During this phase, scintillation areas of 5 m^2 and 10 m^2 and two optical sensors, photomultiplier tubes and silicon photomultipliers, were tested. In this work, we present the status and performance of the array currently equipped with silicon photo- multipliers, along with the timing performance and geometry reconstruction of modules equipped with photomultiplier tubes. Analyses and results are based on both laboratory and field measure- ments. Scintillation areas of 10 m^2 and silicon photomultipliers as readout have been selected as the baseline design for the full-scale AMIGA array.