arXiv subjects

V. I. Umatov

Publications and source records attributed to V. I. Umatov.

58 records · Page 4Linked to original sources

arXiv2009

New Results for Double-Beta Decay of Mo-100 to Excited Final States of Ru-100 Using the TUNL-ITEP Apparatus

The coincidence detection efficiency of the TUNL--ITEP apparatus designed for measuring half-life times of two-neutrino double-beta decay transitions to excited final states in daughter nuclei has been measured with a factor of 2.4 improved accuracy. In addition, the previous measuring time of 455 days for the study of the Mo-100 two-neutrino double-beta decay to the first excited 0+ state in Ru-100 has been increased by 450 days, and a new result (combined with the previous measurement obtained with the same apparatus) for this transition is presented: T_(1/2) = [5.5 (+1.2/-0.8) (stat) +/- 0.3 (syst)] x 10^20 y. Measured two-neutrino double-beta decay half-life times to excited states can be used to test the reliability of nuclear matrix element calculations needed for determining the effective neutrino mass from zero-neutrino double-beta decay data. We also present new limits for transitions to higher excited states in Ru-100 which, if improved, may be of interest for more exotic conjectures, like a bosonic component to neutrino statistics.

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arXiv2008

Search for $β^+$EC and ECEC processes in $^{112}$Sn and $β^-β^-$ decay of $^{124}$Sn to the excited states of $^{124}$Te

Limits on $β^+$EC and ECEC processes in $^{112}$Sn and on $β^-β^-$ decay of $^{124}$Sn to the excited states of $^{124}$Te have been obtained using a 380 cm$^3$ HPGe detector and an external source consisting of natural tin. A limit with 90% C.L. on the $^{112}$Sn half-life of $0.92\times 10^{20}$ y for the ECEC(0$ν$) transition to the $0^+_3$ excited state in $^{112}$Cd (1871.0 keV) has been established. This transition is discussed in the context of a possible enhancement of the decay rate by several orders of magnitude given that the ECEC$(0ν)$ process is nearly degenerate with an excited state in the daughter nuclide. Prospects for investigating such a process in future experiments are discussed. The $β^-β^-$ decay limits for $^{124}$Sn to the excited states of $^{124}$Te were obtained on the level of $(0.8-1.2)\times 10^{21}$ y at the 90% C.L.

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arXiv2005

Double Beta Decay of $^{100}$Mo to Excited Final States

A systematic study of the inclusive ($0ν+2ν$) double beta ($ββ$) decay of $^{100}$Mo to various excited final states of $^{100}$Ru was performed. Utilizing two large HPGe detectors operated in coincidence, a search for the subsequent deexcitation gamma-gamma cascades was conducted. A 1.05-kg sample of isotopically enriched (98.4%) $^{100}$Mo was investigated for 455 days, yielding an unambiguous observation of the double beta decay of $^{100}$Mo to the $0_1^+$ state (1130.3 keV) of $^{100}$Ru. This excited final state decays via the $0_1^+ \to 2_1^+ \to 0_{gs}^+$ sequence (with $E_{\gamma1}$ = 590.8 keV and $E_{\gamma2}$ = 539.5 keV), and 22 such coincidence events were detected, with a continuous background estimated to be 2.5 events. This counting rate corresponds to a decay half-life for the $ββ($0^+ rightarrow 0_1^+)$ transition of $T_{1/2}^{(0ν+2ν)} = [ 6.0^{+1.9}_{-1.1} (\rm{stat}) \pm 0.6(\rm{syst})] \times 10^{20}$ years. Lower limits on decay half-lives were achieved for higher excited final states.

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arXiv2003

Liquid Argon Ionization Detector for Double Beta Decay Studies

A multisection liquid argon ionization detector was developed by the DBA collaboration to study the double beta- decay of $^{100}$Mo. The experiment was carried out in the Gran Sasso underground laboratory in Italy. The detector design and main characteristics are described. The $ββ(2ν)$ decay of $^{100}$Mo was observed and its half-life measured: $T_{1/2}=[7.2 \pm 0.9(stat) \pm 1.8(syst)] \times 10^{18}$ yr. Limits on the 0$ν$ and 0$νχ^{0}$ modes of the decay were obtained: $T_{1/2}> 8.4(4.9) \times 10^{21}$ yr and $T_{1/2}> 4.1(3.2)\times 10^{20}$ yr at 68% (90%) C.L., respectively. In addition the upper limits on the $^{42}$Ar content and $^{222}$Rn activity in liquid Ar were found to be $4.3 \times 10^{-21}$ g/g and $1.2 \times 10^{-3}$ Bq/kg, respectively.

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