MUON FLUX ESTIMATION IN THE ANDES UNDERGROUND LABORATORY

Abstract

The ANDES Underground Laboratory is being planned and designed to be one of the largest and most shielded laboratories in the Southern Hemisphere, which will be located in the Andes Range, in the area of the current Paso de agua Negra that connects the provinces of San Juan (Argentina) and Elqui (Chile). The diversity of experiments that are being planned, including experiments for the direct and indirect search of dark matter and neutrino precision physics, require a precision knowledge of the flux of high-energy atmospheric muons within the laboratory. These are produced during the interaction of astroparticles with energies between 1012 and 1018 eV denominated of high and ultra-high energy with the Earth’s atmosphere. In the high-energy component, muons with energies of tens of TeV can be found, capable of passing through thousands of meters of rock. Previous estimates made from reasonable assumptions about the type of rock expected in the area showed that the expected muon flux was compatible with other underground laboratories at an equivalent depth. In this work, extensive atmospheric showers flux simulations were performed at the laboratory site. Afterwards, there was a selection of those muons with sufficient energy to reach the laboratory based on their angle of incidence and the height at which they enter the mountain. Then a transfer function was modeled using the new geological studies currently available that allow us to have a detailed model of the rock distribution inside the mountain. Finally, the interaction of these muons with the different types of rock was calculated numerically along their way to the laboratory using the continuous slow down approximation, thus obtaining that the expected muon flux within the laboratory is 1,47±0,02 day⁻¹ m⁻² sr⁻¹ .