Thesis

Anti-neutrino Physics in SNO+

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domain:

  Experimental Particle Physics

• Supervisor:

  Sofia Andringa

• Co-Supervisor:

  Amelia Maio

• Institution:

  Faculdade de Ciências - Universidade de Lisboa

• Host Institution:

  Laboratório de Instrumentação e Física Experimental de Partículas

• Abstract:

  The first observations of geo-neutrinos, i.e. anti-neutrinos produced by natural radioactivity in the planet's crust and mantle, are recent but are already being used to test Earth models; anti-neutrinos produced in nuclear reactors have been classically used in neutrino physics, namely for the study of neutrino oscillations. The separation between those two signals is usually based on energy alone, and we plan to increase it by using also directional information for the first time. The Sudbury Neutrino Observatory (SNO) is a large volume neutrino detector located in the SNOLAB underground laboratory in Canada. SNO has demonstrated that solar neutrinos do change flavour and thus have a small, but non-zero, mass. The SNO+ experiment will replace SNO's heavy water target by liquid scintillator, that will provide sensitivity to several new low energy neutrino physics measurements, and in particular anti-neutrinos. The SNO+ experiment will have commissioning data taking periods already in 2015, and scintillator data taking is expected in 2016. The LIP group is responsible for several aspects of the calibration system – PMT and scintillator optical calibration, source insertion mechanism – as well as for the anti-neutrino analysis. The expected rates of anti-neutrinos are small, but they can be clearly identified by the coincidence of a positron annihilation followed by a neutron capture, even with the background from the Tellurium decays. The positron energy and the neutron initial direction follow the anti-neutrino kinematics, and we aim to use the difference between the positions of the positron and neutron signals to help in the separation of the fluxes of reactor and geo-neutrinos, which come preferably from different directions. The final goal is the interpretation of the measured fluxes and spectra in terms of neutrino mixing and geological models. The proposed work plan will involve all aspects of the anti-neutrino data analysis, from the development of selection algorithms for neutron identification and coincidence techniques, useful to identify anti-neutrinos (but also for the identification of background events), to the final signal measurement and interpretation. The work will include also participation in in-situ activities in SNOLAB, including in the early stages the commissioning of the calibration systems, and later on, data-taking and calibration data analysis.