Mb as an alternative muon-related parameter for the photon search

M. ROTH; A. BOTTI; B. GARCÍA; M. JOSEBACHUILI; M. PERLIN; E. SANTOS; D. SCHMIDT; A. YUSHKOV; F. SÁNCHEZ; B. ANDRADA; J. M. FIGUEIRA; J. HULSMAN; S. MUELLER; M. RONCORONI; G. SILLI; B. WUNDHEILER; N. GONZÁLEZ; A. ETCHEGOYEN; A. CANCIO; E. HOLT; D. MELO; D. RAVIGNANI; C. SARMIENTO-CANO; A. TABOADA

Otro; Nota Interna de la Colaboración Pierre Auger; 2017

To be submitted as an internal note to the Pierre Auger Collaboration-------------------------------------------------------------------------------------------------------------------In the search for ultra-high-energy photons, it is crucial to define composition-sensitiveparameters capable of adequately rejecting the hadronic background. In this work, weexplore the parameter M b that combines the muon densities measured by the AMIGAburied scintillation detectors and their distance to the shower core, similarly to the well-known S b parameter. We analyze the discrimination power of M b between photon andproton primaries in the 10 17 eV energy scale. The aim of this work is to tune M b to beapplied in the 433 m Infill (AERAlet) whose central station is equipped with a buriedscintillation detector. We found that M b with b = 2 can separate photons from protonsknowing the number of muons in the nearest detector with a merit factor of at least ∼ 4.By imposing a cut on the value of M 2 , 99.90% of the background (proton) events can berejected while keeping ∼ 97.5% of the photon events.