Jeremy Cushman

The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale cryogenic experiment designed to search for neutrinoless double-beta decay in tellurium-130. The experiment consists of 988 ultracold tellurium dioxide bolometric crystals, which act as both the double-beta decay sources and detectors, in a close-packed configuration. This dissertation presents a search for neutrinoless double double-beta decay with the first two months of CUORE data. An observation of this decay would be direct evidence of lepton number violation and unambiguously prove that neutrinos are Majorana particles.

 

We analyze the first 83.6 kg yr of tellurium dioxide exposure and find no evidence for neutrinoless double-beta decay. We set a half-life limit of 1.5 × 10^25 yr (90% C.L.) by combining this exposure with that from two predecessor experiments, CUORE-0 and Cuoricino. With this data, we set the world-leading limit on the rate of neutrinoless double-beta decay in tellurium-130. The CUORE bolometer array is characterized by an effective energy resolution of 7.7 ± 0.5 keV FWHM and background of 0.014 ± 0.002 counts/(keV kg yr) at the double-beta decay Q-value. This is the lowest background level achieved to date in such a large-scale cryogenic experiment, meeting our expectations and requirements for this search.