Speaker
Description
Neutrinoless double-beta decay ($0\nu\beta\beta$) is a key process for testing the Majorana nature of neutrinos and probing the effective Majorana neutrino mass. The Majorana nature of neutrinos is important for understanding their fundamental properties and may provide insight into the origin of the matter-dominated universe.
The KamLAND-Zen experiment at the Kamioka underground laboratory has been at the forefront of the search for $0\nu\beta\beta$ for over a decade. Following the initial phase (KamLAND-Zen 400) launched in 2011, an upgraded configuration (KamLAND-Zen 800) began operation in 2019 with a doubled xenon mass and a substantial reduction in uranium and thorium backgrounds. Combined analyses of these datasets, incorporating advanced techniques such as neural-network-based particle identification, have set world-leading limits to date on the effective Majorana neutrino mass, reaching 36--156 meV with different nuclear matrix elements.
The KamLAND-Zen collaboration is advancing toward the next phase of the experiment, KamLAND2-Zen. The upgrade features a highly purified liquid scintillator, light-collecting mirrors, high quantum-efficiency photomultiplier tubes, and new readout electronics to increase sensitivity.
The decommissioning of the KamLAND-Zen detector has been completed. Construction of the KamLAND2-Zen detector is scheduled to begin this year, starting with the installation of photomultiplier tubes and light-collecting mirrors, and preparations are currently underway. In parallel, development of the liquid scintillator, the data acquisition system and other components is progressing, together with the establishment of the analysis framework. First light of KamLAND2 is expected in early 2028, followed by the start of $0\nu\beta\beta$ search with KamLAND2-Zen in early 2029 to further investigate the fundamental properties of neutrinos.
This poster presentation will outline the current status and prospects of these research and development efforts.