Low background measurement in CANDLES-III for studying the neutrino-less double beta decay of ${}^{48}$Ca

Abstract

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 (${}^{nat.}$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 ${}^{nat.}$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.

arXiv comment26 pages, 9 figures, submitted to Physical Review D

References in corpus (17)

• Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen
• Neutrinoless Double-Beta Decay: Status and Prospects
• Status and Future of Nuclear Matrix Elements for Neutrinoless Double-Beta Decay: A Review
• Final Results of GERDA on the Search for Neutrinoless Double-$\beta$ Decay
• Search for Neutrinoless Double-Beta Decay with the Complete EXO-200 Dataset
• Precise half-life values for two neutrino double beta decay
• Improved Limit on Neutrinoless Double-Beta Decay in ${}^{130}$Te with CUORE
• Search for Zero-Neutrino Double Beta Decay in 76Ge with the Majorana Demonstrator
• On the alpha activity of natural tungsten isotopes
• Large-scale shell-model analysis of the neutrinoless $\beta \beta$ decay of ${}^{48}$Ca
• Neutrino-less Double Beta Decay of 48Ca studied by CaF2(Eu) Scintillators
• Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of ${}^{48}\mathrm{Ca}$ with the NEMO-3 detector
• New determination of double-beta-decay properties in 48Ca: high-precision Q-value measurement and improved nuclear matrix element calculations
• Average and recommended half-life values for two-neutrino double beta decay: upgrade-2019
• The energy calibration system for CANDLES using (n, γ) reaction
• Measurement of ambient neutrons in an underground laboratory at Kamioka Observatory
• $\mu$TCA DAQ system and parallel reading in CANDLES experiment

Cited by in corpus (3)

• Toward the discovery of matter creation with neutrinoless double-beta decay
• Neutrinoless double beta decay and the muonium-to-antimuonium transition in models with a doubly charged scalar
• Scintillation light increase of carbontetrafluoride gas at low temperature