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V. V. Kuzminov

Publications and source records attributed to V. V. Kuzminov.

At least 73 records · Page 4Linked to original sources
arXiv2014

Production, characterization and operation of $^{76}$Ge enriched BEGe detectors in GERDA

The GERmanium Detector Array (GERDA) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double beta decay (0νββ) of $^{76}$Ge. Germanium detectors made of material with an enriched $^{76}$Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of the experiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new $^{76}$Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in GERDA during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the $^{76}$Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of GERDA Phase~II.

physics.ins-det↗
arXiv2014

First result of the experimental search for the 9.4 keV solar axion reactions with Kr-83 in the copper proportional counter

The experimental search for solar hadronic axions is started at the Baksan Neutrino Observatory of the Institute for Nuclear Researches Russian Academy of Science. It is assumed that axions are created in the Sun during M1-transition between the first thermally excited level at 9.4 keV and the ground state in Kr-83. The experiment is based on axion detection via resonant absorption process by the same nucleus in the detector. The big copper proportional counter filled with krypton is used to detect signals from axions. The experimental setup is situated in the deep underground low background laboratory. No evidence of axion detection were found after the 26.5 days data collection. Resulting new upper limit on axion mass is m_{A} < 130 eV at 95% C.L.

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arXiv2014

Sources of the systematic errors in measurements of Po-214 decay half-life time variations at the Baksan deep underground experiments

The design changes of the Baksan low-background TAU-1 and TAU-2 set-ups allowed to improve a sensitivity of Po-214 half-life (τ) measurements up to the 2.5 x 10^{-4} are described. Different possible sources of systematic errors influencing on the $τ$-value are studed. An annual variation of Po-214 half-life time measurements with an amplitude of A=(6.9 \pm 3) x 10^{-4} and a phase of (ϕ=93 \pm 10) days was found in a sequence of the week-collected τ-values obtained from the TAU-2 data sample with total duration of 480 days. 24 hours' variation of the τ-value measurements with an amplitude of A=(10.0 \pm 2.6) x 10^{-4} and phase of (ϕ=1 \pm 0.5) hours was found in a solar day 1 hour step τ-value sequence formed from the same data sample. It was found that the Po-214 half-life averaged at 480 days is equal to (163.45 \pm 0.04) mks.

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arXiv2014

First result of the experimental search for the 2K-capture of Xe-124 with the copper proportional counter

First result of experiment for searching of 2K-capture of Xe-124 with the large-volume copper proportional counter is given. The 12 litre sample with 63.3% (44 g) of Xe-124 was used in measurements. The limit on the half-life of Xe-124 with regard to 2K(2ν)-capture for the ground state of Te-124 has been found: T_{1/2} > 4.67x10^{20} y (90% C.L.). A sample with volume 52 L comprising of Xe-124 (10.6 L - 58.6 g) and Xe-126 (14.1 L - 79.3 g) will used at the next step of the experiment to increase a sensitivity of 2K-caption of Xe-124 registration. In this case sensitivity to the investigated process will be at the level of S=1.46 x 10^{21} y (90% C.L.) for 1 year measurement.

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arXiv2014

The background in the neutrinoless double beta decay experiment GERDA

The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta decay of 76Ge. The signature of the signal is a monoenergetic peak at 2039 keV, the Q-value of the decay, Q_bb. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around Q_bb. The main parameters needed for the neutrinoless double beta decay analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around Q_bb with a background index ranging from 17.6 to 23.8*10^{-3} counts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at Q-bb is dominated by close sources, mainly due to 42K, 214Bi, 228Th, 60Co and alpha emitting isotopes from the 226Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known gamma peaks, the energy spectrum can be fitted in an energy range of 200 kev around Q_bb with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.

physics.ins-det↗
arXiv2013

Results on neutrinoless double beta decay of 76Ge from GERDA Phase I

Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the Standard Model of particle physics. This Letter reports the results from Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope 76Ge. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kgyr. A blind analysis is performed. The background index is about 1.10^{-2} cts/(keV kg yr) after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of 76Ge, T_1/2 > 2.1 10^{25} yr (90% C.L.). The combination with the results from the previous experiments with 76Ge yields T_1/2 > 3.0 10^{25} yr (90% C.L.).

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arXiv2013

Pulse shape discrimination for GERDA Phase I data

The GERDA experiment located at the LNGS searches for neutrinoless double beta (0νββ) decay of ^{76}Ge using germanium diodes as source and detector. In Phase I of the experiment eight semi-coaxial and five BEGe type detectors have been deployed. The latter type is used in this field of research for the first time. All detectors are made from material with enriched ^{76}Ge fraction. The experimental sensitivity can be improved by analyzing the pulse shape of the detector signals with the aim to reject background events. This paper documents the algorithms developed before the data of Phase I were unblinded. The double escape peak (DEP) and Compton edge events of 2.615 MeV γ rays from ^{208}Tl decays as well as 2νββ decays of ^{76}Ge are used as proxies for 0νββ decay. For BEGe detectors the chosen selection is based on a single pulse shape parameter. It accepts 0.92$\pm$0.02 of signal-like events while about 80% of the background events at Q_{ββ}=2039 keV are rejected. For semi-coaxial detectors three analyses are developed. The one based on an artificial neural network is used for the search of 0νββ decay. It retains 90% of DEP events and rejects about half of the events around Q_{ββ}. The 2νββ events have an efficiency of 0.85\pm0.02 and the one for 0νββ decays is estimated to be 0.90^{+0.05}_{-0.09}. A second analysis uses a likelihood approach trained on Compton edge events. The third approach uses two pulse shape parameters. The latter two methods confirm the classification of the neural network since about 90% of the data events rejected by the neural network are also removed by both of them. In general, the selection efficiency extracted from DEP events agrees well with those determined from Compton edge events or from 2νββ decays.

physics.ins-det↗
arXiv2012

Working characteristics of the New Low-Background Laboratory (DULB-4900, Baksan Neutrino Observatory)

A concise technical characteristic of a new low-background laboratory DULB-4900 of the BNO INR RAS is presented. The technique and the results of background measurements in the Hall, ordinary box and low-background box are presented. Rn-222 contamination in the laboratory air has been measured by direct detection of gamma-radiation of its daughter Bi-214 distributed over the volume of the low-background box. The results of the data analysis are presented.

physics.ins-det↗
arXiv2011

Results of a search for 2β-decay of Xe-136 with high pressure copper proportional counters in Baksan Neutrino Observatory INR RAS

Search for ββ-decay of Xe-136 with two high pressure proportional counters is carried out in Baksan Neutrino Observatory. The experiment is based on comparision of spectra measured with natural and enriched xenon. The measured halfe life is equal to T_{1/2}=5.5^{+4.6}_{-1.7} \cdot 10^{21} yr (67% C.L.) for ββ2ν-decay mode. No evidence has been found for neutrinoless ββ-decay. The decay half life limit based on data measured during 17280 h is T_{1/2}(ββ0ν)\geq 4.9 \cdot 10^{23} yr (90% C.L.).

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arXiv2011

Experimental test of the time stability of the half-life of alpha-decay Po-214 nuclei

A method and results of an experimental test of the time stability of the half-life of alpha-decay Po-214 nuclei are presented. Two underground installations aimed at monitoring the time stability have been constructed. Time of measurement exceeds 1038 days for one set up and 562 days for the other. It was found that amplitude of possible annual variation of Po-214 half-life does not exceed 0.2% of the mean value. The limit on the deviation of the decay curve from exponent at 0.034\times T_{1/2}<t< 0.1\times T_{1/2} range has been found.

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arXiv2011

Search for 2K(2ν)-capture of Kr-78

Results of a search for Kr-78 double K-capture at the second stage of the experiment with high-pressure copper proportional counters are presented. The method is based on comparison of spectra measured with natural and enriched krypton. The total exposure of the low background measurements is for Kr-78 152 g*yr and for Kr-nat 106 g*yr. An excess of events was observed in the analysis of Kr-78 selected data collected during 2008-2010 years. This excess could correspond to a double K-capture of Kr-78 with the half-life of T_{1/2}(2K,2ν+ 0ν)=[1.4^{+2.2}_{-0.7}]\cdot 10^{22}$ yr (90% C.L.)

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arXiv2010

Results of wavelet processing of the 2K-capture Kr-78 experiment statistics

Results of a search for Kr-78 double K-capture with the large low-background proportional counter (2005-2008 years) at the Baksan Neutrino Observatory are presented. An experimental method and characteristics of detectors are described. Basic features of the digitized pulses processing using wavelet transform are considered. With due account taken of the analysis of individual noise characteristic it has been shown that the appropriate choice of both wavelet characteristics and sequence of processing algorithms allows one to decrease the background in the energy region of useful events with a unique set of characteristics by ~2000 times. New limit on the half-life of Kr-78 with regard to 2K-capture has been found: T_{1/2} >= 2.4E21 yrs (90% C.L.).

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arXiv2010

Pulse Shape Analysis and Identification of Multipoint Events in a Large-Volume Proportional Counter in an Experimental Search for 2K Capture Kr-78

A pulse shape analysis algorithm and a method for suppressing the noise component of signals from a large copper proportional counter in the experiment aimed at searching for 2K capture of Kr-78 are described. These signals correspond to a compound event with different numbers of charge clusters due to from primary ionization is formed by these signals. A technique for separating single- and multipoint events and determining the charge in individual clusters is presented. Using the Daubechies wavelets in multiresolutional signal analysis, it is possible to increase the sensitivity and the resolution in extraction of multipoint events in the detector by a factor of 3-4.

physics.ins-det↗
arXiv2007

Comparative analysis of spectra of the background of the proportional counter filled with Kr, enriched in Kr-78, and with Kr of natural content

The results of the experiment searching for 2K-capture with large low-background proportional counter are presented. The comparison of spectra of the background of the proportional counter filled with Kr enriched in $^{78}$Kr (8400 hr) and with natural Kr (3039 hr) is given. A new limit on the half-life of $^{78}$Kr with regard to 2K-capture, T$_{1/2}\geq2.0\cdot10^{21}$ yrs (95% C.L.) has been obtained.

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arXiv2005

Next stage of search for 2K(2$ν$)-capture of $^{78}$Kr

A technique to search for 2K-capture of $^{78}$Kr with large low-background proportional counter filled with an enriched in $^{78}$Kr up to 99.8% sample of Krypton at a pressure of 4.51 is described in this paper. The results of first measurements are presented. Analysis of data collected during 159 hours yielded new limit to the half-life of $^{78}$Kr with regard to 2K-capture (T$_{1/2}\geq6\cdot10^{21}$ yr (90% C.L.)). Sensitivity of the facility to the process for one year of measurement was evaluated to be $\texttt{S}=1.0\cdot10^{22}$ yr (90% C.L.).

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arXiv2005

Results of a search for 2$β$-decay of $^{136}$Xe with high-pressure copper proportional counters in Baksan Neutrino Observatory

The experiment for the 2$β$-decay of $^{136}$Xe search with two high-pressure copper proportional counters has been held in Baksan neutrino observatory. The search for the process is based on comparison of spectra measured with natural and enriched xenon. No evidence has been found for 2$β$(2$ν$)- and 2$β$(0$ν$)-decay. The decay half lifetime limit based on data measured during 8000 h is T$_{1/2}$$\geq8.5\cdot10^{21}$yr for 2$ν$-mode and T$_{1/2}$$\geq3.1\cdot10^{23}$yr for 0$ν$-mode (90%C.L.).

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