Speaker
Dr
Saori UMEHARA
(Osaka University)
Description
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 system and $^{48}$Ca enrichment.
The system realizes a complete 4$\pi$ active shield
by immersion of the CaF$_{2}$ scintillators in liquid scintillator.
The active shield 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\%).
We have studied $^{48}$Ca enrichment and succeeded
in obtaining enriched $^{48}$Ca although it is a small amount.
Now we have developed the CANDLES III system,
which contained 350 g of $^{48}$Ca without enrichment,
at the Kamioka underground laboratory.
Two improvements, a light-concentration system and a new DAQ system,
were installed for the CANDLES III system.
The light-concentration system improved a energy resolution
by increasing a PMT photo-coverage by 80\%.
The new DAQ system, which is a dead time less system,
improved a rejection efficiency
for a characteristic background origin.
Now we checked detector performance
with the light-concentration system and the new DAQ system.
Here we will report the detector performance for background rejection,
and the expected sensitivity with the light-concentration system and the new DAQ system.
Primary author
Dr
Saori UMEHARA
(Osaka University)
Co-authors
Prof.
Izumi Ogawa
(Fukui University)
Prof.
Ken-ichi Fushimi
(The University of Tokushima)
Prof.
Masaharu Nomachi
(Osaka University)
Prof.
Ryuta Hazama
(Osaka Sangyo University)
Prof.
Sei Yoshida
(Osaka University)
Prof.
Tadafumi Kishimoto
(Osaka University)
