AMIGA Grande: a beyond 2015 proposal with muon counters

A. ALMELA; A. ETCHEGOYEN; B. GARCÍA; M. GÓMEZ BERISSO; N. GONZÁLEZ; J.M. FIGUEIRA; M. JOSEBACHUILI; A. LUCERO; D. MELO; M. PLATINO; D. RAVIGNANI; F. SÁNCHEZ; F. SCHRÖDER; F. SUÁREZ; A. TAPIA CASANOVA; M. VIDELA; O. WAINBERG; B. WUNDHEILER

Otro; Nota interna de la Colaboración Pierre Auger; 2013

Instituto de Tecnologías en Detección y Astropartículas

P { margin-bottom: 0.21cm; direction: ltr; color: rgb(0, 0, 0); font-size: 11pt; line-height: 115%; widows: 2; orphans: 2; }A:link { color: rgb(0, 0, 255); }A.sdfootnoteanc { font-size: 57%; } AMIGA has undergone reviews setup by the Collaboration and has produced several gap notes as below-shown in the bibliography. Suffice to say that composition studies are of paramount importance to understand the transition from galactic to extragalactic sources, to discriminate exotic mechanisms, and for anisotropy searches (e.g. to study composition from the CEN A region). Longitudinal profiles and muon numbers are the most sensitive parameters for such studies. Gamma initiated showers are discriminated straight forwards by their negligible muon contents (more sturdy results are obtained by looking at the change in muon density rather than at its absolute values since the former are less dependent on hadronic models and require less statistics). The current Auger Xmax studies show a tendency to increasing primary mass with energy which is even more clearly appreciated from the Xmax fluctuations. On the other hand both HiRes and Telescope Array find a composition compatible with proton primaries. An independent muon contents measurement will strengthen and cast light on the FD results. P { margin-bottom: 0.21cm; direction: ltr; color: rgb(0, 0, 0); font-size: 11pt; line-height: 115%; widows: 2; orphans: 2; }A:link { color: rgb(0, 0, 255); } A major advantage of AMIGA is that it has already deployed and commissioned 11 muon counters. Its first modules were deployed late in 2009 close to the SD station named Corrientes: electronics as well as mechanical design have demonstrated their long-term performance. Still, two issues need to be address to have an AMIGA muon-counter upgrade. Firstly, AMIGA needs to complete its validation with the twin detector systems and secondly it need to encompass the whole Auger area at a reasonable cost. The former point is being already addressed by the AMIGA Task and in order to address the latter we suggest the following upgrade with a single 10 m2 muon counter per position: a 10% of the Auger area with a muon counter at 1500 m distance, i.e. 160 positions and the remaining 3000 km2 with a muon counter at 3000 m distance, i.e. 360 muon counters.