Towards Gamma-Ray Astronomy at ultra-high energies

N. GONZÁLEZ; A. ALMELA; A. CANCIO; A. FUSTER; E. HOLT; A. LUCERO; M. PERLIN; M. RONCORONI; D. SCHMIDT; A. TABOADA; A. YUSHKOV; F. SÁNCHEZ; B. ANDRADA; L. FERREYRO; B. GARCÍA; J. HULSMAN; D. MELO; M. PLATINO; E. SANTOS; G. SILLI; O. WAINBERG; M. ROTH; A. ETCHEGOYEN; A. BOTTI; J. FIGUEIRA; M. R. HAMPEL; M. JOSEBACHUILI; S. MULLER; D. RAVIGNANI; C. SARMIENTO-CANO; F. SUAREZ; B. WUNDHEILER

PUBLICACION INTERNA DE LA COLABORACION INTERNACIONAL AUGER

PUBLICACION INTERNA DE LA COLABORACION INTERNACIONAL AUGER

Año: 2017 p. 1 - 29

2250-835X

The Auger Observatory has a unique possibility of exploring a new branch of Astronomy:Gamma Astronomy at the highest energies. In the search for ultra-high-energy photons, it is crucial to define composition-sensitive parameters capable of adequately rejecting the hadronic background. In this work, we explore the parameter Mb that combines the muon densities measured by the AMIGA buried scintillation detectors and their distance to the shower core, similarly to the well-known observable Sb. We analyze the discrimination power of Mb between photon and proton primaries in the energy range between EMC = 10**16.5 eV and EMC = 10**17.5 eV. The aim of this work is to tune Mb to be applied in the 433 m Infill array (AERAlet) whose central station is equipped with a buried scintillation detector. We found that Mb with b = 2 can separate photons from protons via the number of muons in the nearest muon detector with a merit factor of at least 5.06 at energies around Erec = 10**17 eV. By imposing a cut on the value of M2 = 0.065, 99.90% of the background (proton) events can be rejected at a 1 confidence level while keeping 79.8% of the photon events for energies above Erec = 10**16.5 eV following a realistic spectrum. These are quite encouraging results.