Departmental Bulletin Paper Discrimination of Cherenkov light in Liquid Scintillator for Neutrinoless Double Beta Decay Experiment

FUKUDA, Yoshiyuki  ,  KAMEI, Yuto  ,  Narengerile  ,  OBATA, Akira  ,  MORIYAMA, Shigetaka  ,  OGAWA, Izumi  ,  GUNJI, Takahiro  ,  HAMAYA, Ryohei  ,  TSUKADA, Satoru

 A liquid scintillator containing a tetrakis(isopropyl acetoacetato)zirconium has been developed for ZICOS experiment. We will use 180 tons of liquid scintillator containing 75 kg of 96Zr in the inner balloon(45 kg in fiducial volume)surrounding 64 % photo coverage of 20 inch photomultiplier. In order to reach the sensitivity ≥1027 years, we have to reduce 95 % of 208Tl decay backgrounds at least. Using Monte Carlo simulation, we could demonstrate new method using the hit pattern of PMT which received Cherenkov light, and could reduce 93 % of 208Tl background with 78 % efficiency for 0νββ signal. For the discrimination of Cherenkov light, we measured the timing pulse shape of Zr loaded liquid scintillator using FADC digitizer, and we found an inconsistent pulse shape at the rise timing with the template of scintillation. Also the event with an inconsistent pulse shape seems to have a directionality.

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