First Study of the PIKACHU Project: Development and Evaluation of High-Purity Gd$_3$Ga$_3$Al$_2$O$_{12}$:Ce Crystals for $^{160}$Gd Double Beta Decay Search

• DOI: 10.48550/arxiv.2402.06830
• Publication Date: 2024-02-09
• Authors: T. Omori; T. Iida; A. Gando; K. Hosokawa; Kei Kamada; K. Mizukoshi; Yasuhiro Shoji; Masao Yoshino; K. Fushimi; Hisanori Suzuki; Kotaro Takahashi
• Keywords: BETA (programming language)

Uncovering neutrinoless double beta decay (0$\nu$2$\beta$) is crucial for confirming neutrinos' Majorana characteristics. The rate of 0$\nu\beta\beta$ theoretically uncertain, influenced by nuclear matrix elements that vary across nuclides. To reduce this uncertainty, precise measurement the half-life neutrino-emitting (2$\nu$2$\beta$) in different nuclides essential. We have launched PIKACHU (Pure Inorganic scintillator experiment KAmioka CHallenging Underground sciences) project to fabricate high-purity Ce-doped Gd$_{3}$Ga$_{3}$Al$_{2}$O$_{12}$ (GAGG) single crystals and use them study $^{160}$Gd. Predictions from two theoretical models on element calculations 2$\nu$2$\beta$ $^{160}$Gd show a significant discrepancy estimated half-lives, differing approximately an order magnitude. If lower estimation holds true, detecting could be achievable with sensitivity enhancement slightly more than magnitude compared prior investigations using Gd$_2$SiO$_5$ (GSO) crystal. successfully developed GAGG purity levels surpassing previous standards through refined purification selection raw materials. Our experiments these indicate feasibility reaching sensitivities exceeding those earlier studies. This paper discusses ongoing development performance evaluation High-purity crystals, along anticipated future prospects experiment.