Search for long-lived superheavy eka-tungsten with radiopure ZnWO4 crystal scintillator

The data collected with a radioactively pure ZnWO4 crystal scintillator (699 g) in low background measurements during 2130 h at the underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (INFN, Italy) were used to set a limit on possible concentration of superheavy eka-W (seaborgium Sg, Z = 106) in the crystal. Assuming that one of the daughters in a chain of decays of the initial Sg nucleus decays with emission of high energy particle (Q > 8 MeV) and analyzing the high energy part of the measured spectrum, the limit N(Sg)/N(W) < 5:5 1014 atoms/atoms at 90% C.L. was obtained (for Sg half-life of 109 yr). In addition, a limit on the concentration of eka-Bi was set by analysing the data collected with a large BGO scintillation bolometer in an experiment performed by another group [L. Cardani et al., JINST 7 (2012) P10022]: N(eka-Bi)/N(Bi) < 1:1 1013 atoms/atoms with 90% C.L. Both the limits are comparable with those obtained in recent experiments which instead look for spontaneous emission of superheavy elements or use the accelerator mass spectrometry.