Development of energy calibration and data analysis systems for the NUCLEUS experiment

TL;DR

This paper presents the development of calibration and data analysis systems for the NUCLEUS experiment, enabling precise measurements of CEvNS using ultra-low threshold cryogenic detectors and advanced analysis frameworks.

Contribution

It introduces a photon-statistic based optical calibration setup, integrates the DIANA analysis framework with NUCLEUS DAQ, and develops a new automatic analysis protocol and discovery potential toolkit.

Findings

Calibration setup successfully tested on detectors

Analysis protocol accurately reproduces early results

Enhanced toolkit for discovery potential analysis

Abstract

Coherent elastic neutrino-nucleus scattering (CEvNS) opens new approaches for the search of new physics beyond the Standard Model. The NUCLEUS experiment aims to use the intense antineutrino flux produced from nuclear reactor cores to perform measurements of the CEvNS cross-section via gram-scale ultra-low threshold cryogenic detectors. A common problem with low threshold detectors is the calibration, since most radioactive sources tend to saturate the dynamical range of the sensors. In this dissertation, a photon-statistic based optical calibration setup has been developed and tested using detectors from the BULLKID R&D project. Both the developed hardware setup and the relative control software allow to automatically perform a full calibration of an array of detectors. During the development of this work, the DIANA analysis framework, developed for the CUORE experiment, has been compatibilized with the NUCLEUS DAQ and a new automatic analysis protocol was developed using the data from the NUCLEUS prototype runs. This protocol proved to be accurate at reproducing the results obtained via a model dependent study performed with an almost event by event inspection that was carried out in the early stages of NUCLEUS. Particular focus was given to the development of an event reconstruction procedure used to measure the energy of events that lie outside the linear response region of the detector. The last activity done for the NUCLEUS experiment was to develop a python based toolkit for the study of the discovery potential of the experiment. This toolkit was originally developed in the early stages of NUCLEUS by J.Rothe and has been intensely upgraded during the work presented in this thesis, in order to deal with different types of statistical checks and procedures.