Phenomenology of Neutrino Interactions for Coherent Neutrino-Nucleus Scattering and Dark Matter Experiments

Despite the success of the Standard Model in describing electromagnetic, weak, and strong forces, several unanswered questions indicate that it is incomplete. Therefore, searching for any deviations from this framework is highly intriguing. This thesis focuses on an in-depth examination of the Standard Model by leveraging the signals from the faintest particle, i.e. the neutrino. To do so, we will exploit neutrino elastic scattering at low energies to search for new physics signatures in coherent elastic neutrino-nucleus scattering (CEvNS) and dark matter experiments. Furthermore, by leveraging the formalism described in the thesis, we will precisely compute the signals from both CEvNS and neutrino elastic scattering off atomic electrons (vES) in the upcoming DarkSide-20k dark matter experiment. Throughout this thesis, we will give a detailed overview of the emerging field of CEvNS searches, describing the main features of the measurements available at the time of writing this thesis, provided by the COHERENT and NCC-1701 detectors. In addition, we will discuss the details of the upcoming NUCLEUS experiment. Using currently available data, we will not only provide insights into electroweak and nuclear physics but also establish some of the strongest existing bounds in the literature on new physics scenarios predicting exotic neutrino properties. We will also deeply investigate the neutrino charge radius, the only non-zero neutrino electromagnetic property predicted by the Standard Model, whose imprint in experimental data is so small that it has never been experimentally observed. By refining the theoretical description of the neutrino charge radius contribution to the CEvNS process, we will obtain competitive bounds on this quantity. In addition, in this thesis, we will explore the existence of new light gauge bosons that can mediate the CEvNS interaction. This work demonstrates the potential of low-threshold CEvNS experiments to impose leading constraints on a variety of light mediator models. Throughout the thesis, we will also study the sensitivity of future COHERENT and NUCLEUS CEvNS experiments in detecting such new physical signatures, as well as their ability to extract electroweak or nuclear physics parameters.