Studies of the performance of the CYGNO experiment in low-energy nuclear recoils detection

In this thesis, I report my contribution to the analysis of data acquired from the Lime prototype detector of the Cygno experiment, whose purpose is exactly the one described in the last paragraphs, with the aim of providing conclusions on the performance in low-energy nuclear recoils detection. In chapter 1, I describe the main cosmological knowledge required to understand the theoretical context of the thesis, starting from the concept of visible matter and then reviewing the astrophysical and cosmological evidences of dark matter, proceeding with a focus on the WIMP candidates and concluding with an overview of the main concepts of experimental techniques in dark matter direct detection. In chapter 2, after a short preamble on the time projection chambers' working principles, I describe the Cygno project approach and technology, together with the specifications of the Lime prototype, a gaseous TPC with optical readout. In chapter 3, I first describe the algorithm for data reconstruction and feature extraction for the reconstructed clusters. Then, the focus is shifted on the first part of my analysis, oriented to the energy data pre-processing for a dataset taken with an Americium-Beryllium neutron source, treating in particular data normalisation, gain non-uniformity correction and light yield calibration. Finally, in chapter 4, I discuss the second part of my analysis, focused on a selected sample of low-energy nuclear recoils induced from the neutron source. First of all, I describe the sample selection strategy, then I provide a first approach to directionality measurements, together with a Monte Carlo simulation to validate the technique. In the end, I discuss how to reconstruct the 3D length using lonely nuclear recoils from the sample, which are easily associated with the corresponding data from PMTs, providing the first insights on possible results and problems.