Détection de Neutrinos provenant de Supernovae à effondrement de cœur

Le résumé fourni par la source

Core Collapse supernovae (CCSNs) emit more light than all the stars in the galaxy from which their progenitor star was born. The remnants of the core collapse supernovae will be visible for centuries. However, information about what occurred in the core is transmitted via a neutrino burst that is emitted ten seconds only after the core bounces. While telescopes have time to point out supernova remnants, particle detectors on Earth expect to see half of the neutrino burst events in the first second after the collapse. The first and only CCSN neutrino signal has been detected in 1987 (SN1987A). Since then, we are still searching for the next one. Detecting a future, new CCSN neutrino burst presents a challenge for particle detectors, necessitating precise timing and energy resolution. Direct dark matter detectors provide a unique environment for investigating the CCSN signal, through mechanisms that are different from what large volume water cerenkov or liquid scintillator detectors are capable to provide. Dark matter detectors are often located underground, protected from cosmic radiation and exhibit ultra-low backgrounds, allowing them to potentially observe cosmic neutrinos, such as those from our Sun, which present around 10^4 times lower fluxes than a CCSN neutrino burst from the Milky Way center. The XENONnT detector is based on a xenon dual phase time projection chamber (TPC), surrounded by a water cerenkov volume that acts as a muon or neutron veto. XENONnT presents then two detection volumes sensitive to CCSN neutrinos: the 5.9 tonnes of liquid xenon in the TPC, where neutrinos are expected to interact via coherent elastic scattering with xenon nuclei (CEνNS); and the water tank with 700 tonnes of ultrapure water doped with Gd salt, compounding the neutron (56 tonnes) and muon (644 tonnes) vetoes, in which neutrinos are expected to induce an inverse beta decay (IBD) reaction. The goal of this thesis is to investigate the CCSN signal in all available detection volumes, with a particular focus on the expected neutrino interactions in the water tank. The thesis manuscript is organized as follows. Chapter 1 covers the physics of the core collapse, while Chapter 2 focuses on neutrinos emission and their propagation that will result in the final detectable neutrino flux at the Earth. This second chapter presents as well the state of the art of CCSN modeling, culminating in the selection of one of the available models that will be used in the CCSN analysis in the next chapters. Chapter 3 opens with a small review of CCSN neutrino detection, then moves to the description of the XENONnT TPC detector. The chapter ends with an original work where the CEνNS are simulated in the TPC. The next two chapters are devoted to the investigation of the CCSN signal in the water tank. In particular, chapter 4 describes the two sensitive volumes, including the micro-physics of the Cerenkov light induced by the CCSN signal. In addition, the predicted IBD rates used for CCSN signal simulation in the water tank are discussed. Chapter 5 addresses the CCSN simulation chain, with an original work on the digitalization of the IBD process in the muon and neutron veto, included in the full GEANT4 simulation chain of the experiment. To test the reliability of the data digitalization, a comparison with data from AmBe calibrations have been used.Finally, this manuscript ends with a conclusion chapter in which the simulation results from CEνNSin the LXe TPC and IBD in the water tank will be summarized. This work has been thought as well to provide precise guidelines for scientists who intend to perform new and updated projections on CCSN detectability for future and larger dark matter detectors.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.