Speaker
Description
The origin of neutrino masses is one of the unsolved puzzles in particle physics. One possibility is that neutrinos have Majorana masses.We can test the Majorana nature of neutrinos by searching for neutrinoless double-beta decay ($0\nu\beta\beta$) events.CANDLE is a project which targets $0\nu\beta\beta$ events from ${}^{48}$Ca using its high Q$_{\beta\beta}$-value of $4.27\,$MeV. We developed a CANDLES-III system with 96 $\mathrm{CaF}_2$ scintillation crystals with natural Ca isotope, which corresponds to $350\,$g of ${}^{48}$Ca.The key to search for $0\nu\beta\beta$ with the CANDLES-III is to identify and remove the $\beta$ decay background events from impurities in $\mathrm{CaF}_2$ crystals. Especially, $\beta$ decay events from ${}^{208}$Tl with Q$_{\beta}$-value of $5.0\,$MeV are dominant background events.
In the proposed talk, an improved sensitivity by a new ${}^{208}$Tl background removal method and the latest results of the search for $0\nu\beta\beta$ will be discussed.
