Status and future prospect of 48Ca double beta decay search in CANDLES

14th International Conference on Topics in Astroparticle and Underground Physics

物理学;天文学

Iida, T.^1 ; Nakajima, K.^2 ; Ajimura, S.^3 ; Batpurev, T.^3 ; Chan, W.M.^3 ; Fushimi, K.^4 ; Hazama, R.^5 ; Kakubata, H.^3 ; Khai, B.T.^3 ; Kishimoto, T.^3 ; Li, X.^3 ; Maeda, T.^3 ; Masuda, A.^2 ; Matsuoka, K.^3 ; Morishita, K.^2 ; Nakatani, N.^5 ; Nomachi, M.^1 ; Noshiro, S.^2 ; Ogawa, I.^2 ; Ohata, T.^3 ; Osumi, H.^6 ; Suzuki, K.^7 ; Tamagawa, Y.^2 ; Tesuno, K.^3 ; Trang, V.T.T.^3 ; Uehara, T.^3 ; Umehara, S.^1 ; Yoshida, S.^3

Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki, Osaka

567-0047, Japan^1

Graduate School of Engineering, University of Fukui, Fukui

910-8507, Japan^2

Graduate School of Science, Osaka University, Toyonaka, Osaka

560-0043, Japan^3

Institute of Socio Arts and Science, University of Tokushima, Tokushima

770-8502, Japan^4

Faculty of Human Environment, Osaka Sangyo University, Daito, Osaka

574-8530, Japan^5

Faculty of Culture and Education, Saga University, Saga

840-8502, Japan^6

Wakasa-wan Energy Research Center, Tsuruga, Fukui

914-0192, Japan^7

关键词: Analysis and simulation;    Double beta decay;    Future prospects;    Lepton number violations;    Light yield;    Majorana;    Neutron capture;    Surrounding materials;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/718/6/062026/pdf
DOI  :  10.1088/1742-6596/718/6/062026

学科分类：天文学(综合)

来源: IOP

【 摘 要 】

The observation of neutrino-less double beta decay (0vßß) would be the most practical way to prove the Majorana nature of the neutrino and lepton number violation. CANDLES studies48Ca double beta decay using CaF2scintillator. The main advantage of48Ca is that it has the highest Q-value (4.27 MeV) among all the isotope candidates for 0vßß. The CANDLES III detector is currently operating with 300kg CaF2crystals in the Kamioka underground observatory, Japan. In 2014, a detector cooling system and a magnetic cancellation coil was installed with the aim to increase light emission of CaF2scintillator and photo-electron collection efficiency of the photo-multipliers. After this upgrade, light yield was increased to 1000 p.e./MeV which is 1.6 times larger than before. According to data analysis and simulation, main background source in CANDLES is turned out to be high energy external gamma-ray originating neutron capture on the surrounding materials, so called (n,γ). Upgrading the detector by installing neutron and gamma-ray shield can reduce the remaining main backgrounds by two order magnitude. In this report, we discuss the detail of (n,γ) and background reduction by additional shielding.