Background studies for the HOLMES experiment

Determining the mass of neutrinos is one of the most compelling topics in particle physics. HOLMES, an experiment for a direct measurement of the neutrino mass, is addressing this subject through a calorimetric approach, exploiting arrays of Low-Temperature Transition-Edge Sensor Detectors (TESs) loaded with ¹⁶³ 163 Ho. The experiment has entered its first phase in 2023, implanting approximately 1 Bq per pixel in an array of 64 detectors. In this work, I present the measurement made before this stage, in order to determine the expected background arising from natural radioactivity and cosmic rays. The significance of this background depends on the activity per pixel, which has yet to be defined based on the result of the first phase.