Reaching for PeVatrons with the future Southern Wide-field Gamma-ray Observatory
PT-CERN Call 2021/2
Instituto Superior Técnico (Universidade de Lisboa)
Laboratório de Instrumentação e Física Experimental de Partículas
This thesis focuses on measuring PeVatrons with the future Southern Wide-field Gamma-ray Observatory (SWGO), which will have the ability to survey the Galactic centre. The recent observation of Galatic PeVatron events by LHAASO shows that it is possible to detect those events provided that the experiment covers sufficiently large areas (order of 1 km2) and has excellent capabilities of identifying the gamma-induced shower events amongst the hadronic background, which in their case is done by deploying buried muon detectors. To find a cost-effective solution for SWGO that allows reaching for bigger array areas with an excellent gamma/hadron discrimination, the following strategy will be employed: - investigate the shower characteristics of PeV electromagnetic and hadronically induced showers to identify quantities that might be combined to the measurement of the number of muons at the ground. For instance, a promising idea is to look at the azimuthal correlations, whose fluctuations are expected to be larger for showers of hadronic origin. - develop dedicated analyses to estimate the muon content in air showers on an event-by-event basis. For instance, statistically remove the electromagnetic signal footprint to find muon signals. - optimization of the detector unit, making it as simpler/cheaper as possible. For instance, studying the use of only one PMT per station in the outer regions of the array. - optimization of the array layout configuration. Such shall be done recurring to genetic algorithms to probe a larger phase space with a limited number of simulations. All these tasks are intertwined and should be iterated upon each other. Ultimately, the sensitivity of SWGO to PeVatrons and physics reach should be investigated. The study on the shower characteristics will also be used to improve the determination of the cosmic ray mass composition and hadronic interaction properties, which might shed some light on the so-called EAS muon puzzle.