Sep 8 – 13, 2013
Asilomar, California
US/Pacific timezone

Search for Neutrino-less Double Beta Decay with CANDLES

Sep 12, 2013, 4:00 PM
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)

Presentation materials

There are no materials yet.