Speaker
Description
Though the maximum energy of the charged cosmic ray observations exceeds 100EeV, the energy frontier of the gamma-ray observations is PeV. In the past years, Tibet ASgamma, HAWC and LHAASO opened a new window of astronomy in the sub-PeV to PeV range, which is important to unveil yet unknown PeV cosmic accelerators in our galaxy. As they are all located in the northern hemisphere, observations in the southern hemisphere have been awaited. Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA) is a new air shower array experiment under construction in the Bolivian Andes to explore the southern gamma-ray sky for the first time in this energy range. In this presentation, we will provide an overview of the ALPACA project, including the initial observational results from a quarter-sized array named ALPAQUITA, which has been operating since 2023. A successful detection of the shadow of the moon, for example, validates the designed performance of the array. We will also discuss the current status of the underground muon detector construction, a critical component for gamma/hadron separation, and outline the plan for the full-scale construction of ALPACA.
