69 research outputs found
On the possibility to search for double beta decay of initially unstable (alpha/beta radioactive) nuclei
Possibilities to search for double beta decay of alpha/beta unstable nuclei,
many of which have higher energy release than "conventional" (beta stable)
double beta decay candidates, are discussed. First experimental half-life
limits on double beta decay of radioactive nuclides from U and Th families
(trace contaminants of the CaWO_4, CdWO_4 and Gd_2SiO_5 scintillators) were
established by reanalyzing the data of low-background measurements in the
Solotvina Underground Laboratory with these detectors (1734 h with CaWO_4,
13316 h with CdWO_4, and 13949 h with Gd_2SiO_5 crystals).Comment: 15 pages, 6 figure
Quest for double beta decay of 160-Gd and Ce isotopes
The double beta decay study of 160-Gd has been performed in the Solotvina
Underground Laboratory with the help of Gd_2SiO_5(Ce) crystal scintillator
(volume 95 cc). The background of the detector in the vicinity of the 2 beta
energy of 160-Gd was reduced to 1.0 cpd/keV kg. The new improved half-life
limits have been established for neutrinoless 2 beta decay of 160-Gd to the
ground and first excited levels of 160-Dy: T1/2 > 2.3(1.3)E21 yr at 68%(90%)
C.L. The T1/2 bounds have been also set for two neutrino mode as well as for 2
beta decay with Majorons emission. Also the limits were established for
different 2 beta decay processes in 136-Ce, 138-Ce and 142-Ce.Comment: 12 pages, 6 figures, submitted to Nucl. Phys.
High sensitivity double beta decay study of 116-Cd and 100-Mo 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 100-Mo and 116-Cd neutrinoless double beta decay. Pilot measurements
with 116-Cd and Monte Carlo simulations show that the sensitivity of the CAMEO
experiment (in terms of the half-life limit for neutrinoless double beta decay)
is (3-5) 10^24 yr with a 1 kg source of 100-Mo (116-Cd, 82-Se, and 150-Nd) and
about 10^26 yr with 65 kg of enriched 116-CdWO_4 crystals placed in the liquid
scintillator of the CTF. The last value corresponds to a limit on the neutrino
mass of less than 0.06 eV. Similarly with 1000 kg of 116-CdWO_4 crystals
located in the BOREXINO apparatus the neutrino mass limit can be pushed down to
m_nu<0.02 eV.Comment: 29 pages, LaTex, 9 eps figure
New limits on di-nucleons decay into invisible channels
Data of the radiochemical experiment [E.L.Fireman, 1978] with 1.7 t of
KC_2H_3O_2, accumulated deep underground during ~1 yr, were reanalyzed to set
limits on di-nucleons (nn and np) decays into invisible channels
(disappearance, decay into neutrinos, etc.). The obtained lifetime bounds
tau_np > 2.1 10^25 yr and tau_nn > 4.2 10^25 yr (at 90% C.L.) are better (or
competitive) than those established in the recent experiments.Comment: 3 pages, accepted in JETP Letter
The event generator DECAY4 for simulation of double beta processes and decay of radioactive nuclei
The computer code DECAY4 is developed to generate initial energy, time and
angular distributions of particles emitted in radioactive decays of nuclides
and nuclear (atomic) deexcitations. Data for description of nuclear and atomic
decay schemes are taken from the ENSDF and EADL database libraries. The
examples of use of the DECAY4 code in several underground experiments are
described.Comment: 8 pages, 1 fi
Support of Evidence for Neutrinoless Double Beta Decay
Indirect support for the evidence of neutrinoless double beta decay reported
recently, is obtained by analysis of other Ge double beta experiments, which
yield independent information on the background in the region of Q_(beta-beta).
Some statistical features as well as background simulations with GEANT 4 of the
HEIDELBERG-MOSCOW experiment are discussed which disprove recent criticism.Comment: 15 pages, latex2e, 13 figure
Background Analysis around Q_(beta-beta) for 76Ge Double Beta Decay experiments, and Statistics at Low Count Rates
The background in the region of the Q-value for neutrinoless double beta
decay of 76Ge has been investigated by different methods: Simulation with GEANT
4 of the HEIDELBERG-MOSCOW experiment, analysis of other Ge double beta
experiments.Statistical features of the analysis at very low count rates are
discussed.Comment: 15 pages, latex2e, 12 figure
Vanishing Effective Mass of the Neutrinoless Double Beta Decay?
We stress that massive neutrinos may be Majorana particles even if the
effective mass of the neutrinoless double beta decay m_ee vanishes. We show
that current neutrino oscillation data do allow m_ee = 0 to hold, if the
Majorana CP-violating phases lie in two specific regions. Strong constraints on
three neutrino masses can then be obtained. We find that the neutrino mass
spectrum performs a normal hierarchy: m_1 < m_2 < m_3. A possible texture of
the neutrino mass matrix is also illustrated under the m_ee = 0 condition.Comment: RevTex 9 pages (2 PS figures included). More discussions and
references added. Results partly changed. To appear in Phys. Rev.
Investigation of β + β + and β + /EC decay of 106 Cd
A low background scintillation detector with a CdWO4 crystal of 1.046 kg was used to search for β+β+ and β+/EC processes in 106Cd. For the neutrinoless mode the limits T1/2(0νβ+β+) ≥ 2.2 · 1019 y and T1/2(0νβ+/EC) ≥ 5.5 · 1019 y were obtained with 90% C.L. For the possible two neutrino decay limits of T1/2(2νβ+β+) ≥ 9.2 · 1017 y and 1/2(2νβ+/EC) ≥ 2.6 · 1017 y have been determined with 99% C.L
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