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 a particle (Q(alpha) > 8 MeV) and analyzing the high energy part of the measured alpha spectrum, the limit N(Sg)/N(W) <5.5 x 10(-14) atoms/atom at 90% C.L. was obtained (for Sg half-life of 10(9) 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 (Cardani et al 2012 JINST 7 P10022): N(eka-Bi)/N(Bi)<1.1 x 10(-13) atoms/atom with 90% C.L. Both the limits are comparable with those obtained in recent experiments which instead look for spontaneous fission of superheavy elements or use the accelerator mass spectrometry.