943 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
Lattice distortion in hcp rare gas solids
The lattice distortion parameter has been
calculated as a function of molar volume for the hcp phases of He, Ar, Kr and
Xe. Results from both semi-empirical potentials and density functional theory
are presented. Our study shows that is negative for helium in the
entire pressure range. For Ar, Kr and Xe, however, changes sign from
negative to positive as the pressure increases, growing rapidly in magnitude at
higher pressures.Comment: Submitted to Low. Temp. Phys., 14 pages, 5 figure
Poisson's ratio in cryocrystals under pressure
We present results of lattice dynamics calculations of Poisson's ratio (PR)
for solid hydrogen and rare gas solids (He, Ne, Ar, Kr and Xe) under pressure.
Using two complementary approaches - the semi-empirical many-body calculations
and the first-principle density-functional theory calculations we found three
different types of pressure dependencies of PR. While for solid helium PR
monotonically decreases with rising pressure, for Ar, Kr, and Xe it
monotonically increases with pressure. For solid hydrogen and Ne the pressure
dependencies of PR are non-monotonic displaying rather deep minimums. The role
of the intermolecular potentials in this diversity of patterns is discussed.Comment: Fizika Nizkikh Temperatur 41, 571 (2015
Neutrino-less Double Electron Capture - a tool to research for Majorana neutrinos
The possibility to observe the neutrino-less double decay and thus
to prove the Majorana nature of neutrino as well as provide a sensitive measure
of its mass is a major challenge of to-day's neutrino physics. As an attractive
alternative we propose to study the inverse process, the radiative
neutrino-less double electron capture . The associated monoenergetic
photon provides a convenient experimental signature. Other advantages include
the favourable ratio of the to the competing capture
rates and, very importantly, the existence of coincidence trigger to suppress
the random background. These advantages partly offset the expected longer
lifetimes. Rates for the process are calculated. High Z atoms are
strongly favoured. A resonance enhancement of the capture rates is predicted at
energy release comparable to the atomic level difference. The resonance
conditions are likely to be met for decays to excited states in final nuclei.
Candidates for such studies are considered. The experimental feasibility is
estimated and found highly encouraging.Comment: New figure added, table updated, physical background discusse
CdWO4 scintillating bolometer for Double Beta Decay: Light and Heat anticorrelation, light yield and quenching factors
We report the performances of a 0.51 kg CdWO4 scintillating bolometer to be
used for future Double Beta Decay Experiments. The simultaneous read-out of the
heat and the scintillation light allows to discriminate between different
interacting particles aiming at the disentanglement and the reduction of
background contribution, key issue for next generation experiments. We will
describe the observed anticorrelation between the heat and the light signal and
we will show how this feature can be used in order to increase the energy
resolution of the bolometer over the entire energy spectrum, improving up to a
factor 2.6 on the 2615 keV line of 208Tl. The detector was tested in a 433 h
background measurement that permitted to estimate extremely low internal trace
contaminations of 232Th and 238U. The light yield of gamma/beta, alpha and
neutrons is presented. Furthermore we developed a method in order to correctly
evaluate the absolute thermal quenching factor of alpha particles in
scintillating bolometers.Comment: 8 pages 7 figure
Final results of an experiment to search for 2beta processes in zinc and tungsten with the help of radiopure ZnWO4 crystal scintillators
A search for the double beta decay of zinc and tungsten isotopes has been
performed with the help of radiopure ZnWO4 crystal scintillators (0.1-0.7 kg)
at the Gran Sasso National Laboratories of the INFN. The total exposure of the
low background measurements is 0.529 kg yr. New improved half-life limits on
the double beta decay modes of 64Zn, 70Zn, 180W, and 186W have been established
at the level of 10^{18}-10^{21} yr. In particular, limits on double electron
capture and electron capture with positron emission in 64Zn have been set:
T_{1/2}(2\nu 2K) > 1.1 10^{19} yr, T_{1/2} (0\nu 2\epsilon) > 3.2 10^{20} yr,
T_{1/2} (2\nu \epsilon \beta^+) > 9.4 10^{20} yr, and T_{1/2} (0\nu \epsilon
\beta^+) > 8.5 10^{20} yr, all at 90% C.L. Resonant neutrinoless double
electron capture in 180W has been restricted on the level of T_{1/2} (0\nu
2\epsilon) > 1.3 10^{18} yr. A new half-life limit on alpha transition of 183W
to the metastable excited level 1/2^- 375 keV of 179Hf has been established:
T_{1/2} > 6.7 10^{20} yr.Comment: This is an author-created, un-copyedited version of an article
published in J. Phys. G: Nucl. Part. Phys. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher authenticated version
is available online at doi: 10.1088/0954-3899/38/11/11510
Search for double beta decay of Zinc and Tungsten with the help of low-background ZnWO4 crystal scintillators
Double beta processes in 64-Zn, 70-Zn, 180-W, and 186-W have been searched
for with the help of large volume (0.1-0.7 kg) low background ZnWO4 crystal
scintillators at the Gran Sasso National Laboratories of the INFN. Total time
of measurements exceeds 10 thousands hours. New improved half-life limits on
double electron capture and electron capture with positron emission in 64-Zn
have been set, in particular (all the limits are at 90% C.L.): T1/2(0nu2EC)>
1.1e20 yr, T1/2(2nuECbeta+)>7.0e20 yr, and T1/2(0nuECbeta+)>4.3e20 yr. The
different modes of double beta processes in 70-Zn, 180-W, and 186-W have been
restricted at the level of 1e17-1e20 yr.Comment: 20 p., submitted to Phys. Rev.
Searches for neutrinoless double beta decay
Neutrinoless double beta decay is a lepton number violating process whose
observation would also establish that neutrinos are their own anti-particles.
There are many experimental efforts with a variety of techniques. Some (EXO,
Kamland-Zen, GERDA phase I and CANDLES) started take data in 2011 and EXO has
reported the first measurement of the half life for the double beta decay with
two neutrinos of Xe. The sensitivities of the different proposals are
reviewed.Comment: 8 pages, prepared for TAUP 201
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