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A. Yu. Barnyakov

Publications and source records attributed to A. Yu. Barnyakov.

At least 19 recordsLinked to original sources
arXiv2026

Search for the process $e^+e^-\to f_1(1285)$ at the SND detector

In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider, a search is performed for the direct production of the $C$-even $f_1(1285)$ resonance in $e^+e^-$ collisions. The analysis is based on data with an integrated luminosity of about 200 pb$^{-1}$, accumulated in the center-of-mass energy range of 1.14--1.46 GeV, of which about 72 pb$^{-1}$ were recorded near the maximum of the $f_1(1285)$ resonance. The $f_1(1285)$ production cross section at the resonance maximum $\sigma(e^+e^-\to f_1)=(31\pm 13\pm 2)$ pb and the branching fraction $B(f_1(1285)\to e^+e^-)=(3.5\pm 1.4\pm 0.3)\times 10^{-9}$ have been measured. The significance of the observation of the $e^+e^-\to f_1(1285)$ process is $2.5\sigma$. Since the significance is low, we also present the upper limits at the 90% confidence level: $\sigma(e^+e^-\to f_1)<48\mbox{ pb}$ and $B(f_1(1285)\to e^+e^-)<5.4\times 10^{-9}$.

hep-ex↗
arXiv2026

Options for RICH detectors based on silica aerogels for the high-momentum range

Nowadays, several projects of future colliding beam experiments are being considered in the world. Among them are the CEPC (Circular Electron Positron Collider) in China and the FCC (Future Circular Collider) at CERN (Switzerland). To perform experiments on flavor physics in the energy range of the projects an excellent particle identification up to momenta of 30 GeV/c is required. Several concepts of RICH detectors based on aerogel were considered and evaluated with the help of GEANT4 simulation: FARICH (Focusing Aerogel RICH) based on multilayer aerogel with maximal refractive index of 1.008, RICH with Fresnel lens based on aerogel with refractive index of 1.008, RICH based on transparent aerogel fibers with refractive index of 1.008. The results of the simulation are presented. Some results of beam tests at the BINP performed to validate GEANT4 simulation are presented as well.

physics.ins-det↗
arXiv2026

On peculiarities of the annealing process for highly transparent silica-based aerogel tiles manufactured in Novosibirsk

A collaboration between the Boreskov Institute of Catalysis and the Budker Institute of Nuclear Physics (BINP) has been producing silica aerogel blocks for Cherenkov detectors since 1986. Novosibirsk-manufactured aerogel is used in several experiments: KEDR and SND (BINP, Russia), LHCb (CERN, Switzerland), AMS-02 (ISS), and CLAS12 RICH (Jefferson Lab, USA). This work describes key advancements in the production technology for large-scale aerogel radiators used in Ring-Imaging CHerenkov (RICH) detectors. Annealing is one of the major stages of the highly transparent aerogel production in Novosibirsk. Its procedure was investigated in detail and optimized to improve the yield of aerogel tiles useful for the RICH detectors. The optical and mechanical parameters of the largest silica aerogel samples produced in Novosibirsk using the new annealing procedure are presented.

physics.ins-det↗
arXiv2026

Measurement of the $e^+e^-\to\pi^+\pi^-\pi^0$ cross section in the energy region from 0.56 to 1.1 GeV with the SND detector

The precise measurement of the $e^+e^-\to\pi^+\pi^-\pi^0$ cross section is performed in the center-of-mass energy range $E = 560$--1100 MeV using a data sample of 66 pb$^{-1}$ collected in the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider. The systematic uncertainty of the cross section measurement is 0.9\% at the maximum of the $\omega$ resonance and 1.2\% at the maximum of the $\phi$ resonance. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the $e^+e^-\to\pi^+\pi^-\pi^0$ cross section measured by SND from 0.62 to 1.975 GeV is $(45.95\pm0.06\pm 0.47)\times 10^{-10}$. From the fit to the cross section data with the vector meson dominance model, the parameters of the $\omega$, $\rho$, and $\phi$ resonances are obtained. The obtained values of ${\cal B}(\omega\to e^+e^-) {\cal B}(\omega\to 3\pi)$, mass and width of the $\omega$ meson, and ${\cal B}(\rho\to 3\pi)$ have accuracy better than the current world average values.

hep-ex↗
arXiv2026

Measurement of the neutron timelike electric and magnetic form factors ratio at the VEPP-2000 $e^+e^-$ collider

In the experiment to study the e+e->n+anti n process at the VEPP-2000 $e^+e^-$ collider, the ratio |GE|/|GM| of the neutron timelike electric and magnetic form factors has been measured. The experiment was carried out with the SND detector in the center-of-mass energy range 1890-2000 MeV in eight energy points with an integrated luminosity of 83 inv.pb. The |GE|/|GM| ratio is determined by the analyzing the distribution of the polar angle of the produced antineutron. The measured |GE|/|GM| value in the energy range under study is between 1.0 and 1.5 with an average value of 1.21+-0.13.

hep-ex↗
arXiv2025

Measurement of the $e^+e^-\to\eta\gamma$ cross section near the $\phi(1020)$ resonance with the SND detector

In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider, the $e^+e^-\to\eta\gamma$ cross section is measured in the energy range $E = 980 - 1060$ MeV. The measurement is carried out in the $\eta\to 2\gamma$ decay mode. Data with an integrated luminosity of 73 pb$^{-1}$ collected in 2018 and 2024 are used in the analysis. The measured cross section is the most accurate to date and is higher compared to other measurements. From the fit to the cross section data with the vector meson dominance model, the value of the product of the branching fractions $B(\phi\to e^+e^-)B(\phi\to \eta\gamma)$ has been obtained.

hep-ex↗
arXiv2025

The branching fraction measurements of $J/\psi$ decay into $\rho \eta$ and $\phi \eta$ final states

We present measurements of the branching fractions for the $J/\psi$ meson decays into the $\rho\eta$ and $\phi\eta$ final states, based on data collected with the KEDR detector at the VEPP-4M collider. The data set consisted of 4.93 million $J/\psi$ events. The resulting branching fractions are: - $\mathcal{B}(J/\psi \to \rho\eta) = (2.04 \pm 0.58 \pm 0.39)\times 10^{-4}$, - $\mathcal{B}(J/\psi \to \phi\eta) = (7.82 \pm 1.17 \pm 0.58) \times 10^{-4}$, where the first uncertainty is statistical and the second one is systematic. In the study of the $\rho\eta$ decay, the dynamics of $J/\psi\to\pi^+\pi^-\eta$ is analyzed. The hints from contributions of $\rho(1450)\eta$ and $a^{\pm}_2\pi^{\mp}$ intermediate states are observed. Additional measured branching fractions in the model that includes $\rho(1450)\eta$ and $a^{\pm}_2\pi^{\mp}$ are: - $\mathcal{B}(J/\psi \to \pi^+\pi^-\eta) = (4.73 \pm 0.49 \pm 1.17)\times10^{-4}$, - $\mathcal{B}(J/\psi \to (a_2^+\pi^- + a_2^- \pi^+)) = (1.05\pm 0.37 \pm 0.34)\times 10^{-3}$, - $\mathcal{B}(J/\psi \to \rho(1450)\eta \to \pi^+\pi^-\eta) < 1.51 \times 10^{-4}$, at a confidence level of 90\%. All results are consistent with previous studies.

hep-ex↗
arXiv2025

New measurement of D0 and D+ meson masses with the KEDR detector

Using the 4.9 pb$^{-1}$ statistics collected at the peak of the $\psi(3770)$ resonance with the KEDR detector at the VEPP-4M electron-positron collider, we measured the masses of the neutral and charged D mesons: $M_{D^0} = 1865.100 \pm 0.210 (stat) \pm 0.046 (syst) MeV,$ and $M_{D^+} = 1869.560 \pm 0.288 (stat) \pm 0.109 (syst) MeV$.

hep-ex↗
arXiv2024

Measurement of the $e^+e^-\to K_SK_L$ cross section near the $\phi(1020)$ resonance with the SND detector

The cross section for the $e^+e^-\to K_SK_L$ process is measured in the center-of-mass energy range from 1000 MeV to 1100 MeV in the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider. The measurement is carried out in the $K_S\to 2\pi^0$ decay mode. Data with an integrated luminosity of 20 pb$^{-1}$ recorded in 2018 at 18 energy points are used in the analysis. The systematic uncertainty in the measured cross section at the maximum of the $\phi$ resonance is 0.9%. The mass, width of the $\phi$ meson, and the product of the branching fractions $B(\phi\to K_SK_L)B(\phi\to e^+e^-)$ are determined from the fit to the cross-section energy dependence.

hep-ex↗
arXiv2024

Cross section of the process $e^+e^-\to n\bar{n}$ near the threshold

The $e^+e^-\to n\bar{n}$ cross section was measured at center of mass (c.m.) energies from the threshold to 1908 MeV. The experiment to measure the cross section has been carried out at the VEPP-2000 $e^+e^-$ collider in 13 energy points. The SND detector is used to detect the produced neutron-antineutrons ($n\bar{n}$) events. A special time measurement system on the calorimeter was used to select the time-delayed $n\bar{n}$ events. The measured $e^+e^-\to n\bar{n}$ cross section is 0.4--0.6 nb. The neutron effective timelike form factor in the energy range under study varies from 0.3 to 0.6.

hep-ex↗
arXiv2024

Search for the process $\mathbf{\it e^+e^-\to\eta^{\prime}\gamma}$ in the energy range $\mathbf{\it \sqrt{s}}$ = 1.075 -- 2 GeV

The results of the search for the $e^+e^-\to\eta^{\prime}\gamma$ process in the center-of-mass energy range from 1.075 to 2 GeV are presented. We analyze data with an integral luminosity of 746 pb$^{-1}$ accumulated with the SND detector at the $e^+e^-$ collider VEPP-2000 in 2010--2024. The $\eta^{\prime}\to\eta\pi^0\pi^0$ decay is used in the analysis, with the subsequent $\eta$ and $\pi^0$ decays into $\gamma\gamma$. Upper limits not exceeding 13 pb have been set on the $e^+e^-\to\eta^{\prime}\gamma$ cross section at the 90\% confidence level.

hep-ex↗
arXiv2023

Measurement of the neutron timelike electromagnetic form factor with the SND detector

The results of the measurement of the $e^+e^- \to n \bar{n}$ cross section and effective neutron timelike form factor are presented. The data taking was carried out in 2020-2021 at the VEPP-2000 $e^+e^-$ collider in the center-of-mass energy range from 1891 to 2007 MeV. The general purpose nonmagnetic detector SND is used to detect neutron-antineutron events. The event selection is performed using the time-of-flight technique. The measured cross section is 0.4-0.6 nb. The neutron form factor in the energy range under study varies from 0.3 to 0.2.

hep-ex↗
arXiv2023

Study of the process $e^+e^- \to \omega\pi^0 \to \pi^+\pi^-\pi^0\pi^0$ in the energy range $1.05-2.00$ GeV with SND

The process $e^+e^- \to \omega\pi^0 \to \pi^+\pi^-\pi^0\pi^0$ is studied in the center-of-mass energy region $1.05-2.00$ GeV using data with an integral luminosity of about 35 pb$^{-1}$ collected with the SND detector at the VEPP-2000 $e^+e^-$ collider. In the energy range under study, the value of the measured Born cross section varies from 0.7 to 18 nb. The statistical uncertainty of the cross section is $2-23$%, while the systematic uncertainty is in the range of $3.0-14.2$%. The results are consistent with previous measurements but have better accuracy.

hep-ex↗
arXiv2022

Measurement of the branching fraction of $J/\psi\rightarrow\rho\pi$ at KEDR

We present the study of the decay $J/\psi \rightarrow \rho\pi$. The results are based on of 5.2~million $J/\psi$ events collected by the KEDR detector at the VEPP-4M collider. The branching fractions are measured to be $\B(J/\psi \rightarrow \rho\pi) = \big(2.072\pm 0.017 \pm 0.062 \big)\cdot 10^{-2}$ and $\B(J/\psi \rightarrow \pi^+\pi^-\pi^0) = \big(1.878 \pm 0.013 \pm 0.051 \big)\cdot 10^{-2}$, where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.

hep-ex↗
arXiv2022

Experimental study of the $e^+e^-\to n\bar n$ process at the VEPP-2000 $e^+e^-$ collider with the SND detector

The process $e^+e^-\to n\bar n$ is studied in the experiment at the VEPP-2000 $e^+e^-$ collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic calorimeter is used to select nnbar events. The value of the measured cross section in the center-of-mass energy range from 1.894 to 2 GeV varies from 0.5 to 0.35 nb. The effective neutron timelike form factor is derived from the measured cross section and compared with the proton form factor. The ratio of the neutron electric and magnetic form factors is obtained from the analysis of the antineutron polar angle distribution and found to be consistent with unity.

hep-ex↗
arXiv2021

Study of the process $e^+e^- \to ηηγ$ in the energy range $\sqrt{s} = \mbox{1.17--2.00}$ GeV with the SND detector

The process $e^+e^-\toηηγ$ is studied in the center-of-mass energy range 1.17-2.00 GeV using data with an integrated luminosity of 201 pb$^{-1}$collected by the SND detector at the VEPP-2000 $e^+e^-$ collider. The $e^+e^-\toηηγ$ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $ϕη$ intermediate state. Our result on the $e^+e^-\toηηγ$ cross section is consistent with the $e^+e^-\toϕη$ measurement in the $ϕ\to K^+ K^-$ mode. The search for radiative processes contributing to the $e^+e^-\toηηγ$ cross section is performed, and no significant signal is observed.

hep-ex↗
arXiv2020

Measurement of the $e^+e^- \to K^+ K^- π^0$ cross section with the SND detector

The process $e^+e^-\to K^+K^-π^0$ is studied with the SND detector at the VEPP-2000 $e^+e^-$ collider. Basing on data with an integrated luminosity of 26.4~pb$^{-1}$ we measure the $e^+e^-\to K^+K^-π^0$ cross section in the center-of-mass energy range from 1.28 up to 2 GeV. The measured mass spectrum of the $Kπ$ system indicates that the dominant mechanism of this reaction is the transition through the $K^{\ast}(892)K$ intermediate state. The cross section for the $ϕπ^0$ intermediate state is measured separately. The SND results are consistent with previous measurements in the BABAR experiment and have comparable accuracy. We study the effect of the interference between the $ϕπ^0$ and $K^\ast K$ amplitudes. It is found that the interference gives sizable contribution to the measured $e^+e^- \to ϕπ^0\to K^+K^-π^0$ cross section below 1.7 GeV.

hep-ex↗