8-13 September 2013
Asilomar, California
US/Pacific timezone

Search for Neutrino-less Double Beta Decay with CANDLES

12 Sep 2013, 16:00
Asilomar, California

Asilomar, California

Asilomar Conference Grounds, 800 Asilomar Avenue, Pacific Grove, CA 93950-3704
Oral Double Beta Decay Double Beta Decay/ Neutrino Mass V


Dr Saori UMEHARA (Osaka University)


CANDLES is the project to search for neutrino-less double beta decay (0$\nu\beta\beta$) of $^{48}$Ca. 0$\nu\beta\beta$ is acquiring great interest after the confirmation of neutrino oscillation which demonstrated nonzero neutrino mass. Measurement of 0$\nu\beta\beta$ provides a test for the Majorana nature of neutrinos and gives an absolute scale of the effective neutrino mass. In order to search for 0$\nu\beta\beta$ of $^{48}$Ca, we proposed CANDLES system by using CaF$_{2}$ scintillators. The CANDLES system aims at a high sensitive measurement by a characteristic detector structure and $^{48}$Ca enrichment. The detector structure realizes a complete 4$\pi$ active shield by immersion of the CaF$_{2}$ scintillators in liquid scintillator. The active shield by the liquid scintillator leads to a low background condition for the measurement. On the other band, $^{48}$Ca enrichment is also effective for the high sensitive measurement, because natural abundance of $^{48}$Ca is very low (0.19\%). This means that an improvement of sensitivity by enrichment is a maximum of 20 times for the neutrino mass. However $^{48}$Ca enrichment is generally difficult and expensive. Therefore we started the study of $^{48}$Ca enrichment and succeeded in obtaining enriched $^{48}$Ca although it is a small amount. We have developed the CANDLES III system, which contained 350 g of $^{48}$Ca without enrichment, at the Kamioka underground laboratory. In 2012 we installed a light-concentration system in the CANDLES III system in order to improve a energy resolution. A photo-coverage was about twice larger than the one without the light-concentration system. And we started a 0$\nu\beta\beta$ measurement and have data of a measurement time for 3 months. Here we will report the detector performance for background rejection, the result of the measurement and the expected sensitivity with the light-concentration system.

Primary author

Dr Saori UMEHARA (Osaka University)


Prof. Sei Yoshida (Osaka University) Prof. Tadafumi Kishimoto (Osaka University) Prof. masaharu Nomachi (Osaka University)

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