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Ibragimova, T. V.

Publications and source records attributed to Ibragimova, T. V..

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Gallium neutrino absorption cross section and its uncertainty

In the recent Baksan Experiment on Sterile Transitions (BEST), a suppressed rate of neutrino absorption on a gallium target was observed, consistent with earlier results from neutrino source calibrations of the SAGE and GALLEX/GNO solar neutrino experiments. The BEST Collaboration, utilizing a 3.4 MCi 51 Cr neutrino source, found observed-to-expected counting rates at two very short baselines of 𝑅 = 0.791 Β± 0.05 and 0.766 Β± 0.05, respectively. Among recent neutrino experiments, BEST is notable for the simplicity of both its neutrino spectrum, line neutrinos from an electron-capture source whose intensity can be measured to a estimated precision of 0.23%, and its absorption cross section, where the precisely known rate of electron capture to the gallium ground state, 71 Ge ⁒(π‘’βˆ’, 𝜈 𝑒 )⁒ 71 Ga ⁒(g.s.), establishes a minimum value. However, the absorption cross section uncertainty is a common systematic in the BEST, SAGE, and GALLEX/GNO neutrino source experiments. Here, in this work, we update that cross section, considering a variety of electroweak corrections and the role of transitions to excited states, to establish both a central value and reasonable uncertainty, thereby enabling a more accurate assessment of the statistical significance of the gallium anomalies. Results are given for 51 Cr and 37 Ar sources. The revised neutrino capture rates are used in a reevaluation of the BEST and gallium anomalies.

electroweak interactions in nuclear physics↗
DOE OSTI2022

Search for electron-neutrino transitions to sterile states in the BEST experiment

The Baksan Experiment on Sterile Transitions (BEST) probes the gallium anomaly and its possible connections to oscillations between active and sterile neutrinos. Based on the Gallium-Germanium Neutrino Telescope (GGNT) technology of the SAGE experiment, BEST employs two zones of liquid Ga target to explore neutrino oscillations on the meter scale. Oscillations on this short scale could produce deficits in the 71 Ge production rates within the two zones, as well as a possible rate difference between the zones. From July 5th to October 13th 2019, the two-zone target was exposed to a primarily monoenergetic, 3.4-MCi 51 Cr neutrino source 10 times for a total of 20 independent 71 Ge extractions from the two Ga targets. The 71 Ge production rates from the neutrino source were measured from July 2019 to March 2020. At the end of these measurements, the counters were filled with 71 Ge doped gas and calibrated during November 2020. In this paper, results from the BEST sterile neutrino oscillation experiment are presented in details. The ratio of the measured 71 Ge production rates to the predicted rates for the inner and the outer target volumes are calculated from the known neutrino capture cross section. Comparable deficits in the measured ratios relative to predicted values are found for both zones, with the 4⁒𝜎 deviations from unity consistent with the previously reported gallium anomaly. Finally, if interpreted in the context of neutrino oscillations, the deficits give best-fit oscillation parameters of Ξ”β’π‘š 2 = 3.3$^{+∞}{βˆ’2.3}$ eV 2 and sin 2 ⁑2β’πœƒ = 0.42$^{+0.15}{βˆ’0.17}$, consistent with 𝜈 𝑒 β†’πœˆ 𝑠 oscillations governed by a surprisingly large mixing angle.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Results from the Baksan Experiment on Sterile Transitions (BEST)

The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos πœˆπ‘’ observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred to as the β€œgallium anomaly,” which could be interpreted as evidence for oscillations between πœˆπ‘’ and sterile neutrino (𝜈 𝑠 ) states. A 3.414-MCi 51 Cr 𝜈 𝑒 source was placed at the center of two nested Ga volumes and measurements were made of the production of 71 Ge through the charged current reaction, 71 Ga ⁒(𝜈 𝑒 ,𝑒 βˆ’ ) ⁒71 Ge, at two average distances. The measured production rates for the inner and the outer targets, respectively, are [54.9$^{+2.5}_{βˆ’2.4}$⁒(stat) Β± 1.4⁒(syst)] and [55.6$^{+2.7}_{βˆ’2.6}$⁒(stat) Β± 1.4⁒(syst)] atoms of 71 Ge/𝑑. The ratio (𝑅) of the measured rate of 71 Ge production at each distance to the expected rate from the known cross section and experimental efficiencies are 𝑅 in = 0.79 Β± 0.05 and 𝑅 out = 0.77 Β± 0.05. The ratio of the outer to the inner result is 0.97 Β± 0.07, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20%–24% lower than expected, thus reaffirming the anomaly. Furthermore, these results are consistent with 𝜈 𝑒 β†’ 𝜈 𝑠 oscillations with a relatively large Ξ”β’π‘š 2 (>0.5 eV 2 ) and mixing sin 2 ⁑2β’πœƒ (β‰ˆ 0.4).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Sensitivity of Experiments to Oscillation Parameters

The paper describes the capabilities of the three experiments on the search for oscillations on a short baselineβ€”BEST, SOX, and DANSS. It is shown that only the first two experiments have the capabilities for localization of the oscillation parameters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Calorimetric System for Determination of Activity of a Neutrino Source Based on {sup 51}Cr

Within the framework of the BEST experiment project, a calorimetric system was developed to measure the activity of high-intensity (several MCi) neutrino sources based on {sup 51}Cr. In the range of thermal capacities of 250–520 W, the uncertainty of the heat release measurement is less than 0.25%. Taking into account the uncertainty of the energy release value for the {sup 51}Cr decay (0.23%), the activity of the neutrino source can be determined with an accuracy of ∼0.5%.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Counting Characteristics of the Registration System for the Baksan Experiment on Sterile Transitions

β€” Counting characteristics of the system for recording rare events of the {sup 71}Ge decay in the radiochemical gallium Baksan Experiment on Sterile Transitions (BEST) are presented. Events are recorded simultaneously along eight counting channels in the energy range 0.3–16 keV, which include {sup 71}Ge decays in the region of L and K peaks with a total efficiency of up to 75%. The data analysis is based on the recording of the full shape of the leading edge of the charge pulses using a digital oscilloscope.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND β†—
DOE OSTI2017

Search for sterile neutrinos in gallium experiments with artificial neutrino sources

The possibility of the BEST experiment on electron neutrino disappearance with intense artificial sources of electron neutrino {sup 51}Cr is considered. BEST has the great potential to search for transitions of active neutrinos to sterile states with Ξ”m{sup 2} ∼ 1 eV{sup 2} and to set the limits on short baseline electron neutrino disappearance oscillation parameters. The possibility of the further constraints the oscillation parameters region with using {sup 65}Zn source is discussed.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2017

Measurement of the activity and spectrum of internal bremsstrahlung of a {sup 51}Cr source

The activity of the {sup 51}Cr source in the BEST experiment searching for sterile neutrinos is planned to be determined by measuring the spectrum of internal bremsstrahlung. The measurements of activity and the spectrum of internal bremsstrahlung of point low-activity {sup 51}Cr sources with Ge semiconductor detectors are discussed. The accuracy and errors of this measurement method are examined.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND β†—
DOE OSTI2017

Determination of activity of {sup 51}Cr on gamma radiation measurements

A method of determining the activity of intensive distributed -sources on the measurement of the continuous spectrum of radiation, for example the internal bremsstrahlung, is developed. The recurrent formula for reconstructing of a continuous spectrum, registered in a Ge detector, at distorting it in the detector. The method of precise measurements of the spectrum of {sup 51}Cr internal bremsstrahlung using two point sources of low activity is described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND β†—