Search for the nucleon and di-nucleon decay into invisible channels

Data collected deep underground at the Gran Sasso National Laboratory of INFN by using the ≃ 6.5 kg DAMA liquid Xenon scintillator have been analysed to search for nucleon and di-nucleon decays into invisible channels (decay to νiνi or to νiνiνi or to 5νi, etc., with i=e,μ,τ) or disappearance. The considered statistics has been 2257.7 kg×day. The new obtained limits are: τp=1.9×1024 yr, τnn=1.2×1025 yr and τpp=5.5×1023 yr at 90% C.L. The latter values are the same or better than those previously established by the Fréjus Collaboration; in particular, the limits for the NN decay into ντντ are set for the first time.