Low background measurement in CANDLES-III for studying the neutrinoless double beta decay of Ca48

Autor: P. Noithong, K. Akutagawa, M. Tsuzuki, E. Kinoshita, M. Moser, K. Shimizu, M. Shokati, T. Maeda, W. Wang, T. Hiyama, Y. Hirano, S. Maeda, K. Tetsuno, X. Li, Yoichi Tamagawa, M. Doihara, S. Katagiri, B. T. Khai, S. Ajimura, M. S. Soberi, Y. Ikeyama, N. Nakatani, G. Ito, A. Rittirong, A. Kawamura, M. Saka, K. Shamoto, M. Tozawa, Ken-Ichi Fushimi, A. Hirota, K. Kanagawa, H. Kakubata, Masaharu Nomachi, H. Kino, K. K. Lee, K. Ozawa, T. Batpurev, K. Seki, T. Ishikawa, M. Yoshizawa, T. Iga, K. Matsuoka, N. Yotsunaga, Takashi Iida, Y. Takemoto, T. Uehara, D. Tanaka, M. Tanaka, Y. Shinki, K. Suzuki, Ryuta Hazama, K. Yamamoto, Keita Mizukoshi, K. Nakajima, T. Harada, I. Ogawa, Saori Umehara, S. Yoshida, V. T. T. Trang, H. Hiraoka, Y. Kawashima, K. Ichimura, M. Ishikawa, T. Ohata, K. Yasuda, Tadamitsu Kishimoto, Y. Takihira, W. M. Chan
Rok vydání: 2021
Předmět:
Zdroj: Physical Review D. 103
ISSN: 2470-0029
2470-0010
DOI: 10.1103/physrevd.103.092008
Popis: We developed a CANDLES-III system to study the neutrino-less double beta (0$\nu\beta\beta$) decay of $^{48}$Ca. The proposed system employs 96 CaF$_{2}$ scintillation crystals (305 kg) with natural Ca ($^{\rm nat.}$Ca) isotope which corresponds 350\,g of $^{48}$Ca. External backgrounds were rejected using a 4$\pi$ active shield of a liquid scintillator surrounding the CaF$_2$ crystals. The internal backgrounds caused by the radioactive impurities within the CaF$_2$ crystals can be reduced effectively through analysis of the signal pulse shape. We analyzed the data obtained in the Kamioka underground for a live-time of 130.4\,days to evaluate the feasibility of the low background measurement with the CANDLES-III detector. Using Monte Carlo simulations, we estimated the background rate from the radioactive impurities in the CaF$_{2}$ crystals and the rate of high energy $\gamma$-rays caused by the (n, $\gamma$) reactions induced by environmental neutrons. The expected background rate was in a good agreement with the measured rate, i.e., approximately 10$^{-3}$ events/keV/yr/(kg of $^{\rm nat.}$Ca), in the 0$\nu\beta\beta$ window. In conclusion, the background candidates were estimated properly by comparing the measured energy spectrum with the background simulations. With this measurement method, we performed the first search for 0$\nu\beta\beta$ decay in a low background condition using a detector with a Ca isotope, in which the Ca present was not enriched, in a scale of hundreds of kg. The $^{48}$Ca isotope has a high potential for use in 0$\nu\beta\beta$ decay search, and is expected to be useful for the development of a next-generation detector for highly sensitive measurements.
Databáze: OpenAIRE
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