arXiv subjects

V. Kopeikin

Publications and source records attributed to V. Kopeikin.

10 recordsLinked to original sources

arXiv2021

Reevaluating reactor antineutrino spectra with new measurements of the ratio between $^{235}$U and $^{239}$Pu $β$ spectra

We report a reanalysis of the reactor antineutrino energy spectra based on the new relative measurements of the ratio $R=\!^{e}S_5/^{e}S_9$ between cumulative $β$ spectra from $^{235}$U and $^{239}$Pu, performed at a research reactor in National Research Centre Kurchatov Institute (KI). A discrepancy with the $β$ spectra measured at Institut Laue-Langevin (ILL) was observed, indicating a steady excess of the ILL ratio by the factor of $1.054\pm0.002$. We find a value of the ratio between inverse beta decay cross section per fission for $^{235}$U and $^{239}$Pu: $(^5σ_f/^9σ_f)_{KI} = 1.45 \pm 0.03$, and then we reevaluate the converted antineutrino spectra for $^{235}$U and $^{238}$U. We conclude that the new predictions are consistent with the results of Daya Bay and STEREO experiments.

nucl-ex↗

arXiv2004

Antineutrino Background from Spent Fuel Storage in sensitive Searches for theta_13 at Reactors

Sensitive searches for antineutrino oscillations in atmospheric mass parameter region much discussed in recent years are based on accurate comparison of the inverse beta decay positron spectra measured in two (or more) detectors, far and near, stationed e.g. at ~1000 m and ~100 m from the reactor(s). We show that antineutrinos emitted from the stored irradiated fuel can differently distort the soft part of positron spectra measured in the far and near detector and thus mimic (or hide) the oscillation signal

hep-ph↗

arXiv2004

Can Radiogenic Heat Sources Inside the Earth be located by their Antineutrino incoming Directions?

Antineutrinos born in the U and Th decay chains inside the Earth (``Geoneutrinos'') carry out information on the amount and distribution of radiogenic heat sources, which is of fundamental importance for geophysics. Models of the Earth distribute U and Th masses mainly between the continental crust and the lower mantle. It has been much discussed recently that a number of detectors stationed at appropriate geographical sites can separate the crust and mantle contributions. In present work we analyze directional separation of antineutrino signals arriving from the crust and the lower mantle with only one detector. We find that with a ~30-kton liquid scintillation antineutrino spectrometer using $\bar{ν_e}+p \to n + e^{+}$ detection reaction and positron and neutron coordinates reconstruction techniques the U and Th distribution model can roughly be tested. We also consider detector calibration using ~1 MCi commercially available Sr90-Y90 beta source which emits antineutrinos (Emax = 2.28 MeV) in the geoneutrino energy range.

hep-ph↗

arXiv2004

Reactor as a Source of Antineutrinos: Thermal Fission Energy

Deeper insight into the features of a reactor as a source of antineutrinos is required for making further advances in studying the fundamental properties of the neutrino. The relationship between the thermal power of a reactor and the rate of the chain fission reaction in its core is analyzed.

hep-ph↗

arXiv2004

Neutrino Geophysics at Baksan (Part II): Possible Studies of Antineutrino- and Radiogenic Heat Sources in Earth Interior

Antineutrinos born inside the Earth (``geoneutrinos'') carry out information of fundamental importance for understanding of the origin and evolution of our planet. We show that Baksan Neutrino Observatory is one of the best sites for detection and analysis of geoneutrinos using large liquid scintillation spectrometer. Also we present a short story of concept of Earth as antineutrino source (1960 - 2004 yy)

hep-ph↗

arXiv2004

Inverse beta decay reaction in $^{232}$Th and $^{233}$U fission antineutrino flux

Energy spectra of antineutrinos coming from $^{232}$Th and $^{233}$U neutron-induced fission are calculated, relevant inverse beta decay $\bar{ν_e}+p \to n + e^{+}$ positron spectra and total cross sections are found. This study is stimulated by a hypothesis that a self-sustained nuclear chain reaction is burning at the center of the Earth ("Georeactor"). The Georeactor, according to the author of this idea, provides energy necessary to sustain the Earth's magnetic field. The Georeactor's nuclear fuel is $^{235}$U and, probably, $^{232}$Th and $^{233}$U. Results of present study may appear to be useful in future experiments aimed to test the Georector hypothesis and to estimate its fuel components as a part of developments in geophysics and astrophysics based on observations of low energy antineutrinos in Nature.

hep-ph↗

arXiv2004

Neutrino Geophysics at Baksan I: Possible Detection of Georeactor Antineutrinos

J.M. Herndon in 90-s proposed a natural nuclear fission georeactor at the center of the Earth with a power output of 3-10 TW as an energy source to sustain the Earth magnetic field. R.S. Raghavan in 2002 y. pointed out that under certain condition antineutrinos generated in georeactor can be detected using massive scintillation detectors. We consider the underground Baksan Neutrino Observatory (4800 m.w.e.) as a possible site for developments in Geoneutrino physics. Here the intrinsic background level of less than one event/year in a liquid scintillation ~1000 target ton detector can be achieved and the main source of background is the antineutrino flux from power reactors. We find that this flux is ~10 times lower than at KamLAND detector site and two times lower than at Gran Sasso laboratory and thus at Baksan the georeactor hypothesis can be conclusively tested. We also discuss possible search for composition of georector burning nuclear fuel by analysis of the antineutrino energy spectrum.

hep-ph↗

arXiv2003

Search for sterile neutrinos as another research objective of $θ_{13}$ experiments at reactors

Searches for mass-3 component in the electron neutrino flavor state $\sinθ_{13}$ and for sterile neutrinos can be carried out in the same small mixing angle antineutrino oscillation experiment at a reactor. As an example we consider a layout, which involves several movable antineutrino spectrometers, stationed at distances 1700 m $-$ 50 m from a reactor. The experiment can scan neutrino mass parameter interval $\sim$(0.5$-$0.001) eV$^{2}$ and have there typical sensitivity to $\sin^{2}2θ$ at a level of 0.015$-$0.02. The signature for sterile neutrino is disappearance observed at mass parameter $Δm^{2}_{new}$ different from $Δm^{2}_{atm} \approx 2\times 10^{-3}$ eV$^{2}$. In any case existing constraints both on $\sinθ_{13}$ and on sterile neutrinos can considerably be improved.

hep-ph↗

arXiv2003

Components of Antineutrino Emission in Nuclear Reactor

New ${\barν_e},e$ scattering experiments aimed for sensitive searches of the $ν_e$ magnetic moment and projects to explore small mixing angle oscillations at reactors call for a better understanding of the reactor antineutrino spectrum. Here we consider six components, which contribute to the total ${\barν_e}$ spectrum generated in nuclear reactor. They are: beta decay of the fission fragments of $^{235}$U, $^{239}$Pu, $^{238}$U and $^{241}$Pu, decay of beta-emitters produced as a result of neutron capture in $^{238}$U and also due to neutron capture in accumulated fission fragments which perturbs the spectrum. For antineutrino energies less than 3.5 MeV we tabulate evolution of ${\barν_e}$ spectra corresponding to each of the four fissile isotopes vs fuel irradiation time and their decay after the irradiation is stopped and also estimate relevant uncertainties. Small corrections to the ILL spectra are considered.

hep-ph↗

arXiv2002

The Kr2Det project: Search for mass-3 state contribution |U_{e3}|^2 to the electron neutrino using a one reactor - two detector oscillation experiment at Krasnoyarsk underground site

The main physical goal of the project is to search with reactor antineutrinos for small mixing angle oscillations in the atmospheric mass parameter region around Δm^{2}_{atm} ~ 2.5 10^{-3} eV^2 in order to find the element U_{e3} of the neutrino mixing matrix or to set a new more stringent constraint (U_{e3} is the contribution of mass-3 state to the electron neutrino flavor state). To achieve this we propose a "one reactor - two detector" experiment: two identical antineutrino spectrometers with $\sim$50 ton liquid scintillator targets located at ~100 m and ~1000 m from the Krasnoyarsk underground reactor (~600 mwe). In no-oscillation case ratio of measured positron spectra of the \bar{ν_e} + p \to e^{+} + n reaction is energy independent. Deviation from a constant value of this ratio is the oscillation signature. In this scheme results do not depend on the exact knowledge of the reactor power, nu_e spectra, burn up effects, target volumes and, which is important, the backgrounds can periodically be measured during reactor OFF periods. In this letter we present the Krasnoyarsk reactor site, give a schematic description of the detectors, calculate the neutrino detection rates and estimate the backgrounds. We also outline the detector monitoring and calibration procedures, which are of a key importance. We hope that systematic uncertainties will not accede 0.5% and the sensitivity U^{2}_{e3} ~4 10^{-3} (at Δm^{2} = 2.5 10^{-3} eV^2) can be achieved.

hep-ex↗