Some Comments to the Neutrinoless Double Beta-Decay Search Projects K. Takahashi, KEK • One of the Most Important and Long Term Experiments in Particle Physics Research is the one,such as, Proton Decay Search, and Neutrinoless Double Beta Decay Search. • Proton Decay is for a Search for Baryon Number Non-Conservation Research. • Neutrinoless Double Beta Decay Search is a Search for Lepton Number non-Conservation Research, that also relates to Majorana-Character of Neutrino.

Since observation of Neutrino Oscillation means that neutrinos have some definitive mass,an observation of Double Beta Decay without neutrino could tell us some values for neutrino mass. • Examples of double beta decay nuclei:

• Experimental Methods for Detection; Search for Neutrinoless Double Beta Decay • Calorimetric Detectors ; (Ionization, Bolometric, & Scintillation ) • Tracking Detection ; Important Signals for decay-events ; Q-values or Energy Release. Ionization density for particle-identification, Detection of decaying vertex , Identification of decaying tracks , Rejection of background events . • Call for International Collaboration !!