First search for 2ε, εβ+ decay of 162Er and new limit on 2β- decay of 170Er to the first excited level of 170Y

The first search for double electron capture (2ε) and electron capture with positron emission (εβ+) of 162Er to the ground state and to several excited levels of 162Dy was realized with 326 g of highly purified erbium oxide. The sample was measured over 1934 h by the ultra-low background HP Ge γ spectrometer GeCris (465 cm3) at the Gran Sasso underground laboratory. No effect was observed, the half-life limits were estimated at the level of limT_1/2 ~ 10^{15} - 10^{18} yr. A possible resonant 0ν KL1 capture in 162Er to the 2^+_1 782.7 keV excited state of 162Dy is restricted as T_1/2 > 5.0×10^{17} yr at 90% C.L. A new improved half-life limit T_1/2 > 4.1×10^{17} yr was set on the 2β− decay of 170Er to the 2^+ 84.3 keV first excited state of 170Yb

High sensitivity 2β decay study of 116Cd and 100Mo with the BOREXINO counting test facility (CAMEO project)

The unique features (super-low background and large sensitive volume) of the CTF and BOREXINO set ups are used in the CAMEO project for a high sensitivity study of 100Mo and 116Cd neutrinoless 2β decay. Pilot measurements with 116Cd and Monte Carlo simulations show that the sensitivity of the CAMEO experiment (in terms of the half-life limit for 0ν2β decay) is ≈4×1024 yr with a 1 kg source of 100Mo and ≈1026 yr with ≈100 kg of enriched 116CdWO4 crystals placed in the liquid scintillator of the CTF. The last value corresponds to a limit on the neutrino mass of mν, ≤ 0.06 eV. Similarly with 1000 kg of 116CdWO4 crystals located in the BOREXINO apparatus the neutrino mass limit can be pushed down to mν ≤ 0.02 eV.link_to_subscribed_fulltex

First search for 2ε, εβ+ processes in 168Yb

The double-electron capture and the electron capture with positron emission in 168Yb have been investigated for the first time at the STELLA facility of the Gran Sasso underground laboratory (Italy) measuring 371 g of highly purified ytterbium oxide placed on the end-cap of a 465 cm3 ultra-low-background high purity Germanium detector (HPGe). No gamma associated to double beta processes in 168Yb have been observed after 2074 h of data taking. This has allowed setting the half-life limits on the level of T_1/2 circa 10^14 -10^18 yr at 90% C.L. Particularly, a lower half-life limit on a possible resonant neutrinoless double-electron capture in 168Yb to the 1403.7 keV excited state of 168Er is set as T_1/2 higher/equal 1.9 x 10^18 yr at 90% C.L. Half-life limits T_1/2^2nu(0nu) higher/equal 4.5(4.3) x 10^16 yr were set on the 2 neutrino(0 neutrino) 2beta^- decay of 176Yb to the 84.3 keV first excited level of 176Hf

First direct search for 2EC, ECbeta+ decay of 144Sm and 2beta- decay of 154Sm

The first direct search for the double electron capture (2EC) and the electron capture with positron emission (ECβ+) in 144Sm to the ground state and to the excited levels of 144Nd was realized by measuring — over 1899 h — a 342 g sample of highly purified samarium oxide (Sm2O3) with the ultra-low background HP-Ge γ spectrometer GeCris (465 cm^3) at the STELLA facility of the Gran Sasso National Laboratory (LNGS). No effect was observed and half-life limits were estimated at the level of T1/2 ∼ (0.1–1.3)×10^20 yr (90% C.L.). Moreover, for the first time half-life limits of the double beta (2β−) decay of 154Sm to several excited levels of 154Gd have been set; they are at the level of T1/2 ∼ (0.06–8) × 10^20 yr (90% C.L.)

Preliminary results on the search for 100Mo 2β decay to the first excited 0_1^+ level of 100Ru

Molybdenum sample with mass of near 1 kg, enriched in 100Mo at 99,5 %, is used to confirm or reject previous reports on observation of 2β2ν decay of 100Mo to the first excited 01+ level of 100Ru at E(01+) = 1130,5 keV. Data are collected in the low-background set-up with 4 HP Ge detectors, each of 225 cm3 volume, in the Gran Sasso Underground Laboratory (Italy). After 1927 h of measurements, the reached sensitivity to the half-life is ∼5 1020 y; it does not allow to make definite conclusions on existence of the process searched for. Further measurements are in progress

Search for rare processes at Gran Sasso

New results achieved by the DAMA collaboration on the search for rare processes in the underground Gran Sasso National Laboratories (LNGS) of the INFN are presented. In particular, the following searches have been summarized: i) search for the alpha activity of Eu-151; ii) measurement of 2 beta 2 nu decay of Mo-100 to the first excited 0(1)(+) level of Ru-100; iii) search for double beta processes ill Zn-64