Measurement of the double beta decay half-life of ¹⁰⁰Mo to the 0⁺₁ excited state, and ⁴⁸Ca to the ground state in the NEMO 3 experiment

• Main Author: King, Shiva
• Published: University College London (University of London) 2009
• Subjects: 500
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.564573

NEMO 3 is a double beta decay experiment situated in the Fréjus tunnel which runs between France and Italy. If neutrinoless double beta decay is observed it will prove the neutrino is a Majorana particle and may potentially become the most sensitive method of measuring the absolute neutrino mass. It would also have huge implications for not only particle physics, but also nuclear physics, astrophysics and cosmology. The study of two-neutrino double beta decay gives us a better understanding of the nuclear models used to calculate the nuclear matrix elements, which are so important in extracting new physics parameters from the neutrinoless double beta decay search. The purpose of this thesis is primarily to report on the measurement of the two neutrino double beta decay of two isotopes, ^{100}Mo and ^{48}Ca, currently inside the NEMO 3 detector. The double decay of ^{100}Mo to the O^{+}_{1} excited state of ^{100}Ru is studied as well as the double beta decay of ^{48}Ca to the ground state of ^{48}Ti. The two neutrino half-life measurement for ^{100}Mo is found to be T^{2\upsilon}_{1/2}(O^+\rightarrow O^{+}_1}) = 5.70^{+1.15}_{-0.82} (stat) \pm 0.77 (syst.) \times 10^{20} yrs. This being the first result where all the final states have been measured. For ^{48}Ca, the two neutrino half-life is T^{2\upsilon}_{1/2}(g.s. \rightarrow g.s.) = 4.44^{+0.49}_{-0.40}(stat.) \pm 0.29 (syst.) \times 10^{19} yrs, which is the worlds most accurate measurement of this decay process. A limit on the neutrinoless double beta decay of ^{48}Ca has also been obtained.