arXiv subjects

O. M. Zherebtsov

Publications and source records attributed to O. M. Zherebtsov.

At least 19 recordsLinked to original sources

arXiv2026

Precision studies of neutron decay, left-right asymmetry model of weak interaction, CP-violation and baryon asymmetry of the Universe

An analysis of the latest, most accurate experimental data on neutron decay points to the need to extend the Standard Model by introducing a right vector boson admixture $W_R$. A left-right asymmetry model of the weak interaction is presented, in which the sign of the mixing angle $W_R$ and $W_L$ is reversed upon transition from $W^-$ to $W^+$. In this model, CP violation occurs due to the presence of a right vector boson admixture. The model parameter, the mixing angle, $\zeta$=-(2.7$\pm$0.9)$\cdot$10$^{-3}$ is derived from neutron decay - lifetime and decay asymmetries - as well as from studies of proton decay in nuclei, the so-called superallowed $0^+$-$0^+$ transitions. An estimate for the mass $W_R$ $M_{W_R}$=(340$\pm$60) GeV is given by the relation: from the parameter $\delta$=(5.5$\pm$1.8)$\cdot$10$^{-2}$, which is the ratio of the squares of the mass states of vector bosons. The possibility of describing CP-violation effects in neutral meson oscillations within the left-right asymmetry weak interaction model with parameters $\delta$ and $\zeta$ is investigated. It is shown that within this model, CP violation effects in the decays of $K^0$-mesons, $D^0$-mesons, $B^0$-mesons, and $B^0_s$-mesons can be successfully described. Moreover, the sign of CP violation is opposite for particles and antiparticles, i.e., the CP violation phase is equal to $\pm\pi$/2, which corresponds to 100% CP violation. The results of calculations within the left-right asymmetry model with parameters $\delta$ and $\zeta$ are confirmed by experimental results with neutral mesons. The formation of baryon asymmetry in the Universe is considered in a left-right asymmetry model of weak interaction with an admixture of a right vector boson with different signs of the mixing angle with $W^-$ and $W^+$.

hep-ph↗

arXiv2026

CP-violation effects in neutral meson oscillations in the left-right weak interaction model

An analysis of the latest, most accurate experimental data on neutron decay indicates the need to expand the Standard Model by introducing an admixture of the right vector boson $W_R$ with a mixing angle of $\zeta = -0.039\pm0.014$ with the left vector boson $W_L$ and a ratio of the squares of the masses of $W_1$ and $W_2$ equal to $\delta = 0.070\pm0.010$. In this regard, the possibility of describing CP-violation effects in neutral meson oscillations within the framework of the left-right weak interaction model with parameters $\delta$ and $\zeta$ was investigated. It was shown that within this model, CP violation effects in the decays of $K^0$-mesons, $D^0$-mesons, $B^0$-mesons, and $B_s^0$-mesons can be successfully described. The results of calculations within the extended left-right model with parameters $\delta$ and $\zeta$ are confirmed by experimental results. Thus, the nature of CP violation is related to the presence of a right-handed vector boson admixture.

hep-ph↗

arXiv2024

Analysis of experimental data on neutron decay for the possibility of the existence of the right vector boson $W_R$

The analysis of the latest most accurate experimental data on neutron decay for the possibility of the existence of the right vector boson $W_R$ is carried out. As a result of the analysis within the framework of the left-right symmetric model, it was found that there is an indication of the existence of the right vector boson $W_R$ with a mass of $M_{W_R}=304_{-20}^{+24} \text{GeV}$, and a mixing angle with $W_L: \zeta = -0.039\pm 0.014$. It is shown that this result does not contradict the experiments at colliders to search for a hypothetical vector boson. In addition, it is shown that it is possible to describe the effects of CP violation in decays of neutral $K$-mesons, $D$-mesons and $B_s^0$ using the parameters of the extended left-right symmetric model obtained from neutron decay, i.e. squared masses of the left and right bosons ratio and the mixing angle. The formation of baryon-lepton asymmetry of the Universe is considered within the framework of the left-right model of weak interaction with CP violation. A new experimental design for measuring neutron decay asymmetries with increased accuracy is presented.

hep-ph↗

arXiv2024

Sterile neutrinos, dark matter and Standard Model extended by right-handed neutrinos

Joint analysis of the results of the Neutrino-4 experiment and the data of the GALLEX, SAGE and BEST experiments confirms the parameters of neutrino oscillations declared by the Neutrino-4 experiment $(Δm_{14}^2= 7.3 \text{eV}^2$ and $\sin^2 2θ_{14} \approx 0.36)$ and increases the confidence level to $5.8σ$. Such a sterile neutrino thermalizes in cosmic plasma, contributes 5% to the energy density of the Universe, and can explain 15-20% of dark matter. It is discussed that the extension of the neutrino model by introducing two more heavy sterile neutrinos in accordance with the number of types of active neutrinos but with very small mixing angles to avoid thermalization will make it possible to explain the large-scale structure of the Universe and bring the contribution of sterile neutrinos to the dark matter of the Universe to the level of 27%. Sterile neutrinos are essentially right-handed neutrinos. The dynamic process of the dark matter generation, consisting of three right-handed neutrinos, is presented. Expansion of the Standard Model by introducing right-handed neutrinos seems possible. The scheme of masses and the scheme of mixing flavors are considered.

hep-ph↗

arXiv2024

Appearance of neutrino asymmetries in the process of expansion of the Universe, hierarchy of neutrino masses and CP violation

In this work, we study the appearance of neutrino asymmetries during the expansion of the Universe. A mathematical model based on differential equations was used to describe the processes of neutrino oscillations considering CP violation and neutrino collisions. An analysis of the emergence of neutrino asymmetry due to collisions of neutrinos with each other and due to CP violation during neutrino oscillations is presented. It was discovered that the asymmetry bifurcates into two states with positive and negative asymmetry for the inverse hierarchy of neutrino masses. A state with a normal hierarchy of neutrino masses is unstable and is not realized. It is shown that the maximum CP violation is realized. The influence of this process on the dispersion of the primordial $^4\text{He}$ mass fraction is calculated, which is confirmed by astrophysical observations. Thus, the inverse hierarchy of neutrino masses is realized. The CP violation in neutrino oscillations is maximum and the phase is $δ_{13}=270^\circ (-π/2)$

hep-ph↗

arXiv2023

The result of the Neutrino-4 experiment, sterile neutrinos and dark matter, the fourth neutrino and the Hubble constant

A brief analysis of the result of the Neutrino-4 experiment and the results of other experiments on the search for a sterile neutrino is presented. It is noted that a joint analysis of the results of the Neutrino-4 experiment and the data of the GALLEX, SAGE and BEST experiments confirms the parameters of neutrino oscillations declared by the Neutrino-4 experiment ($Δm^2_{14} = 7.3\text{eV}^2$ and $\sin^{2}2θ_{14}\approx 0.36$) and increases the confidence level to $5.8σ$. An estimate of the contribution of sterile neutrinos with these parameters to the energy density of the Universe is made. It amounted to 5.3%. It is discussed that the extension of the neutrino model by introducing two more heavy sterile neutrinos in accordance with the number of types of active neutrinos will make it possible to explain the large-scale structure of the Universe and bring the contribution of sterile neutrinos to the dark matter of the Universe to the level of 27%. Possible contradictions between the measured sterile neutrino parameters and cosmological constraints are analyzed. It is shown that, based on modern astrophysical data, it is impossible to draw a definite conclusion in favor of the model of three or four neutrinos. It is noted that the introduction of the fourth neutrino removes the Hubble tension problem without contradictions with cosmic microwave background observed by the Planck collaboration. The influence of lepton asymmetry on the comparison of models of three or four neutrinos is considered. An estimate was made for the upper limit of the lepton asymmetry $L_e< 0.02$. The possibility of the appearance of lepton asymmetry due to CP violation during oscillations into sterile neutrinos is discussed.

hep-ph↗

arXiv2023

The Result of the Neutrino-4 Experiment and the Cosmological Constraints on the Sterile Neutrino

We present a short discussion of the Neutrino-4 experimental results and the results of other experiments searching for the sterile neutrino. We estimated the contribution of the sterile neutrino with parameters $Δm^2_{14} = 7.3\text{eV}^2$ and $\sin^2 2θ_{14} = 0.36$ obtained in the Neutrino-4 experiment to the energy density of the Universe. We address the contradiction between the measured sterile neutrino parameters and the constraints on the sterile neutrino from cosmology. With this article, we want to draw attention to the problem of the contradiction between experiment and theory, in order to inspire the search for theoretical models that include a sterile neutrino with mass in the region of several eV, and to the necessity to sufficiently increase the precision of the experiment.

hep-ph↗

arXiv2021

Experiment Neutrino-4 search for sterile neutrino and results of measurements

The experiment Neutrino-4 had started in 2014 with a detector model and then was continued with a full-scale detector in 2016 - 2021. In this article we describe all steps of preparatory work on this experiment. We present all results of the Neutrino-4 experiment with increased statistical accuracy provided to date. The experimental setup is constructed to measure the flux and spectrum of the reactor antineutrinos as a function of distance to the center of the active zone of the SM-3 reactor (Dimitrovgrad, Russia) in the range of 6 - 12 meters. Using all the collected data, we performed a model-independent analysis to determine the oscillation parameters $Δm_{14}^2$ and $\sin^22θ_{14}$. The method of coherent summation of measurement results allows to directly demonstrate the oscillation effect. We present the analysis of possible systematic errors and the MC model of the experiment, which considers the possibility of the effect manifestation at the present precision level. As a result of the analysis, we can conclude that at currently available statistical accuracy we observe the oscillations at the $2.9σ$ level with parameters $Δm_{14}^2=(7.3\pm0.13_{st}\pm1.16_{sys})\text{eV}^2 = (7.3\pm1.17)\text{eV}^2$ and $\sin^22θ_{14}= 0.36\pm0.12_{stat}(2.9σ)$. Monte Carlo based statistical analysis gave estimation of confidence level at $2.7σ$. We plan to improve the currently working experimental setup and create a completely new setup in order to increase the accuracy of the experiment by 3 times. We also provide a brief analysis of the general experimental situation in the search for sterile neutrinos.

hep-ex↗

arXiv2021

Search for explanation of the neutron lifetime anomaly

All results of the neutron lifetime measurements performed in the last 20 years with the UCN storage method are in a good agreement. These results are consistent with the latest most accurate measurements of the neutron decay asymmetry within the Standard Model. However, there is a significant discrepancy at $3.6σ$ (1% of the decay probability) level between the averaged result of the storage method experiments and the most accurate measurements performed with the beam method. This article addresses the possible causes of such discrepancy. We focused on finding the spectrum of possible systematic corrections in the beam experiment. Four separate sources of the systematic errors which had not been properly addressed in articles dedicated to the beam technique were considered. Two of those sources are related with the motion of protons in an electromagnetic field and the elastic scattering by the residual gas. The third error concerns proton loss in the dead layer of the detector. It is shown the corresponding correction requires a more detailed analysis than that given in the papers describing the beam measurement method. The fourth source of the systematic error is the charge exchange process on the residual gas. The influence of that process was neglected in the beam method experiments. We present arguments that careful analysis of this issue is necessary since the proposed proton losses correction decreases the measured lifetime. For the problem of proton charge exchange on a residual gas, the spectrum of possible corrections is investigated. It is shown that for an accurate calculation of the correction, it is necessary to directly measure the concentration and composition of the residual gas inside the proton trap. The analysis reveals that even presence of only $H_2$ molecules can lead to the significant correction which is the most probable explanation of the neutron anomaly.

nucl-ex↗

arXiv2020

The possible explanation of neutron lifetime beam anomaly

The results of measurements performed using UCN storing method are in good agreement. The latest most accurate measurements of the neutron decay asymmetry and neutron lifetime measurements by storage method are in agreement within the Standard Model. However, there is a significant discrepancy at $3.6σ$ (1% of decay probability) level with beam method experiment. This article discusses the possible causes of discrepancy in the measurements of the neutron lifetime with beam method experiment. The most probable cause, apparently, is the loss of protons in beam method experiment during storage in a magnetic trap due to charge exchange collisions of protons with the residual gas. The proton becomes neutral and leaves the trap, which leads to a decrease in the number of registered protons, i.e. to a decrease in the probability of neutron decay or to an increase in the measured neutron lifetime.

nucl-ex↗

arXiv2020

The first observation of effect of oscillation in Neutrino-4 experiment on search for sterile neutrino (continuation)

We present the results of the Neutrino-4 experiment on search for a sterile neutrino. The experiment has been carried out on the SM-3 reactor having a compact active zone of $42\times42\times35\textrm{cm}^3$ and operating on the highly enriched uranium-235 at 90 MW thermal power. We report the results of the Neutrino-4 experiment of measurements of reactor antineutrino flux and spectrum dependence on the distance in the range 6-12 meters from the center of the reactor core. Using the measured spectrum and the distance dependence of antineutrino flux, we performed the model independent analysis of restrictions on the oscillation parameters $Δm^2_{14}$ and $\sin^2 2θ_{14}$. The method of coherent addition of results of measurements is proposed. It allows us to directly observe the effect of oscillations. We observed the oscillation effect at CL $3.5σ$ in the vicinity of $Δm^2_{14} \approx 7.26\textrm{eV}^2$ and $\sin^2 2θ_{14} \approx 0.38$. Combining the result of the Neutrino-4 experiment and the result of the gallium anomaly effect we obtained value $\sin^2 2θ_{14} \approx 0.35 \pm 0.07 (5σ)$. The analysis of systematics effects is presented. Comparison with results of other experiments is presented. Future prospect of the experiment is discussed. It is necessary to notice that obtained values $\sin^2 2θ_{14} \approx 0.35 \pm 0.07 (5σ)$ and $Δm^2_{14} \approx (7.3 \pm 0.7)\textrm{eV}^2$ allow make assessment on the mass of a neutrino: $m_β \approx 0.8\textrm{eV}$.

hep-ex↗

arXiv2018

Experiment Neutrino-4 and restrictions for sterile neutrino

The experiment "Neutrino-4" started in 2014 on a model, then it was continued on a full-scale detector, and now, has provided the measurement result on dependence of the flux and spectrum of reactor antineutrinos on the distance of 6 - 12 meters from the center of the reactor. One of the main problems is the correlated background from fast neutrons caused by space radiation. Attempts to suppress the background of fast neutrons by sectioning the detector have given some result. The relation of effect/background has improved up to 0.6. As a result, measurements of the difference in the counting rate of neutrino-like events (reactor ON - reactor OFF) have been obtained as dependence on distance from the reactor center. The fit of experimental dependence with the law $1/L^2$ give satisfactory result. The goodness of that fit is 81%. However, there was discovered experimental neutrino spectrum difference from calculated one. With achieved accuracy this difference does not change with distance. Therefore it cannot be interpreted as oscillations. Calculated spectrum form correction for experimental allow us to make proper analysis of oscillation parameters $Δm^2_{14}$ and $\sin^2(2θ)$ limitations. Result of this analysis is exclusion of reactor and gallium anomalies area with 95% CL. Experiment future perspectives are discussed.

physics.ins-det↗

arXiv2017

New experimental limits on neutron - mirror neutron oscillations in the presence of mirror magnetic field

Present probes do not exclude that the neutron ($n$) oscillation into mirror neutron ($n'$), a sterile state exactly degenerate in mass with the neutron, can be a very fast process, in fact faster than the neutron decay itself. This process is sensitive to the magnetic field. Namely, if the mirror magnetic field $\vec{B}'$ exists at the Earth, $n-n'$ oscillation probability can be suppressed or resonantly amplified by the applied magnetic field $\vec{B}$, depending on its strength and on the angle $β$ between $\vec{B}$ and $\vec{B}'$. We present the results of ultra-cold neutron storage measurements aiming to check the anomalies observed in previous experiments which could be a signal for $n-n'$ oscillation in the presence of mirror magnetic field $B'\sim 0.1$~G. Analyzing the experimental data on neutron loses, we obtain a new lower limit on $n-n'$ oscillation time $τ_{nn'} > 17$ s (95 % C.L.) for any $B'$ between 0.08 and 0.17 G, and $τ_{nn'}/\sqrt{\cosβ} > 27 $s (95 % C.L.) for any $B'$ in the interval ($0.06\div0.25$) G.

hep-ex↗

arXiv2017

Experiment NEUTRINO-4 Search for Sterile Neutrino

In order to carry out research in the field of possible existence of a sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. A moveable detector, protected with passive shielding from outer radiation, can be set at distance range 6 to 12 meters from the reactor core. Measurements of antineutrino flux at such short distances from the reactor core are carried out with moveable detector for the first time. The main difficulties of the measurements caused by cosmic background and it heavily decreases the precision of measurements. We present the analysis of measurements at small distances together with the data obtained in measurements at long distances in order to obtain parameters of sterile neutrino.

physics.ins-det↗

arXiv2016

Neutrino-4 experiment on search for sterile neutrino with multi-section model of detector

In order to carry out research in the field of possible existence of sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. The prototype of a multi-section neutrino detector with liquid scintillator volume of 350 l was installed in the middle of 2015. It is a moveable inside the passive shielding detector, which can be set at distance range from 6 to 11 meters from the reactor core. Measurements of antineutrino flux at such small distances from the reactor core carried out with movable detector for the first time. The measurements carried out with detector prototype demonstrated a possibility of measuring a reactor antineutrino flux in difficult conditions of cosmic background at Earth surface.

physics.ins-det↗

arXiv2015

Creation of a neutrino laboratory for search for sterile neutrino at SM-3 reactor

In connection with the question of possible existence of sterile neutrino the laboratory on the basis of SM-3 reactor was created to search for oscillations of reactor antineutrino. A prototype of a neutrino detector with scintillator volume of 400 l can be moved at the distance of 6-11 m from the reactor core. The measurements of background conditions have been made. It is shown that the main experimental problem is associated with cosmic radiation background. Test measurements of dependence of a reactor antineutrino flux on the distance from a reactor core have been made. The prospects of search for oscillations of reactor antineutrino at short distances are discussed.

physics.ins-det↗

arXiv2014

New measurements of neutron electric dipole moment with double chamber EDM spectrometer

The article presents results on neutron electric dipole moment measurements (EDM), made by ILL reactor using PNPI experimental installation. Double chamber magnetic resonance spectrometer with prolonged holding of ultra cold neutrons has been employed. The obtained results at 90% confidence level determine the upper limit for EDM neutron quantity equal to $|d_n| < 5.5 \cdot 10^{-26}$ e$ \cdot$cm.

nucl-ex↗

arXiv2014

On possibility of realization NEUTRINO-4 experiment on search for oscillations of the reactor antineutrino into a sterile state

One has investigated possibility of performing NEUTRINO-4 experiment on search for reactor neutrino oscillations into a sterile state at research reactors. The simulated experiment has been conducted at 16 MW reactor WWR-M in PNPI with the purpose of implementing a full scale experiment with the help of 100 MW reactor SM-3 in RIAR. Background conditions for making such an experiment have been examined at both reactors. The conclusion has been made on possible implementation of a full scale experiment NEUTRINO-4 at the reactor SM-3 in RIAR.

physics.ins-det↗