The SNO+ Journey to $0νββ$

Abstract: SNO+ is a large multipurpose experiment with the ultimate goal of searching for the neutrinoless double beta decay in $^{130}\mathrm{Te}$. After a commissioning phase with water as the target medium, during which acquired data allowed for measurements of solar neutrinos and the detection of reactor antineutrinos, SNO+ is now filled with 780 tonnes of liquid scintillator. The higher light yield of the scintillator enhances the physics capabilities of the experiment, and a physics program including reactor, geo and solar neutrinos is currently underway. The water and unloaded scintillator phases provide crucial commissioning milestones in preparation for the tellurium loading, such as calibrating the detector and making extensive background constraint measurements as components of the final scintillator cocktail are gradually added. In a first phase, 3900~kg of natural tellurium (0.5%) will be added to the scintillator for a predicted sensitivity of about $2\times20^{26}$ years (90% CL) with 3 years of livetime. Higher tellurium loading will follow for predicted sensitivities above $1\times10^{27}$ years (3% loading).