774 research outputs found
Beta decays in investigations and searches for rare effects
Current status of experimental investigations of rare single beta decays
(48Ca, 50V, 96Zr, 113Cd, 113mCd, 115In, 123Te, 180mTa, 222Rn) is reviewed.
Nuclei which decay through single beta decay very often constitute backgrounds
in studies of rare effects like double beta decay, solar neutrinos or dark
matter. Summary of correction factors used in description of forbidden beta
decays is also briefly given.Comment: 4 pages, contribution to the MEDEX'2017 conference, one more
acknowledgment adde
False starts in history of searches for double beta decay, or Discoverless double beta decay
A collection of stories is presented on discoveries of double beta decay
(including neutrinoless one) which were refuted in the subsequent
investigations.Comment: 6 pages, contribution to the Workshop on Calculation of Double Beta
Decay Matrix Elements (MEDEX'11), Prague, June 13-16, 201
Semi-empirical calculation of quenching factors for ions in scintillators
Semi-empirical method of calculation of quenching factors for scintillators
is described. It is based on classical Birks formula with the total stopping
powers for electrons and ions which are calculated with the ESTAR and SRIM
codes, respectively. Method has only one fitting parameter (the Birks factor
kB) which can have different values for the same material in different
conditions of measurements and data treatment. A hypothesis is used that, once
the kB value is obtained by fitting data for particles of one kind and in some
energy region (e.g. for a few MeV alpha particles from internal contamination
of a detector), it can be applied to calculate quenching factors for particles
of another kind and for another energies (e.g. for low energy nuclear recoils)
if all data are measured in the same experimental conditions and are treated in
the same way. Applicability of the method is demonstrated on many examples
including materials with different mechanisms of scintillation: organic
scintillators (solid C8H8, and liquid C16H18, C9H12); crystal scintillators
(pure CdWO4, PbWO4, ZnWO4, CaWO4, CeF3, and doped CaF2(Eu), CsI(Tl), CsI(Na),
NaI(Tl)); liquid noble gases (LXe). Estimations of quenching factors for
nuclear recoils are also given for some scintillators where experimental data
are absent (CdWO4, PbWO4, CeF3, Bi4Ge3O12, LiF, ZnSe).Comment: 32 pages; accepted in Astropart. Phy
Spontaneous double alpha decay: First experimental limit and prospects of investigation
Nuclear decays with simultaneous emission of two alpha particles are
energetically possible for a number of nuclides. Prospects of searching for
such kind of decay for nuclides present in the natural isotopic composition of
elements are discussed here. The first experimental limit on half-life for
2alpha decay is set for 209Bi as T1/2 > 2.9e20 y at 90% C.L., using the data of
work [P. de Marcillac et al., Nature 422 (2003) 876]. Theoretical T1/2
estimations for the process are also given. Using these values, which are on
the level of 1e33 y or more, one can conclude that the prospects of
experimental observation of 2alpha decay are very pessimistic.Comment: 8 p., submitted to Nuclear Physics and Atomic Energ
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.
Search for decay of Eu to the first excited level of Pm using underground -ray spectrometry
The alpha decay of Eu to the first excited level of Pm
(, keV) was searched for at the HADES underground
laboratory ( m w.e.). A sample of high purity europium oxide with
mass of 303 g and a natural isotopic composition has been measured over 2232.8
h with a high energy resolution ultra-low background n-type semi-planar HPGe
detector (40 cm) with sub-micron deadlayer. The new improved half-life
limit has been set as yr at 68% C.L.
Possibilities to improve the sensitivity of the experiment, which is already
near the theoretical predictions, are discussed. New half-life limit for
decay of Eu is also set as
yr.Comment: 11 pages, 5 figures, 2 tables, 18 reference
Precise measurement of energy of the first excited state of 115Sn (Eexc = 497.3 keV)
Single beta decay of 115In to the first excited level of 115Sn (Eexc = 497.3
keV) is known as beta decay with the lowest Q value. To determine the Q
precisely, one has to measure very accurately the Eexc value. A sample of tin
enriched in 115Sn to 50.7% was irradiated by proton beam at the U-120
accelerator of INR, Kyiv. The 115Sb radioactive isotope, created in
115Sn(p,n)115Sb reaction, decays with T1/2 = 32 min to 115Sn populating the 497
keV level with ~ 96% probability. The total statistics of ~ 10^5 counts
collected in the 497 keV peak in series of measurements, exact description of
the peak shape and precisely known calibration points around the 497 keV peak
allowed to obtain the value Eexc = 497.342(3) keV, which is the most precise
to-date. This leads to the following Q* value for the decay 115In to 115Sn*: Q*
= 147 +- 10 eV.Comment: 6 pages, 3 figure
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