Searcharxiv⌕ Search

arXiv subjects

A. D. Bukin

Publications and source records attributed to A. D. Bukin.

At least 19 recordsLinked to original sources
arXiv2009

Search for Lepton Flavor Violation Process e^+e^- \to eμin the Energy Region \sqrt{s}=984 -- 1060 MeV and ϕ\to eμDecay

The search for lepton-flavor-violation process e^+e^-\to eμin the energy region \sqrt{s}=984 - 1060 MeV with SND detector at VEPP-2M e^+e^- collider is reported. The model independent 90% CL upper limits on the e^+e^-\to eμcross section, σ_{eμ} < 11 pb, as well as on the corresponding ϕ\to eμbranching fraction, B(ϕ\to eμ) < 2 \times 10^{-6}, for the final particles polar angles 55^\circ<θ<125^\circ, were obtained.

hep-ex↗
arXiv2008

Study of the process e+e-\to μ+μ- in the energy region \sqrt{s}=980, 1040 -- 1380 MeV

The cross section of the process e+e-\toμ+μ- was measured in the SND experiment at the VEPP-2M e+e- collider in the energy region \sqrt{s}=980, 1040 -- 1380 MeV. The event numbers of the process e+e-\toμ+μ- were normalized to the integrated luminosity measured using e+e-\to e+e- and e+e-\toγγprocesses. The ratio of the measured cross section to the theoretically predicted value is 1.006\pm 0.007 \pm 0.016 and 1.005 \pm 0.007 \pm 0.018 in the first and second case respectively. Using results of the measurements, the electromagnetic running coupling constant αin the energy region \sqrt{s}=1040 -- 1380 MeV was obtained <1/α> = 134.1\pm 0.5 \pm 1.2 and this is in agreement with theoretical expectation.

hep-ex↗
arXiv2007

Fitting function for asymmetric peaks

In the paper a new fitting function is suggested, which can essentially increase the existing instrumentation for fitting of asymmetric peaks with the only maximum.

physics.data-an↗
arXiv2007

Measurement of the e+e- -> K+K- cross section in the energy range s**(1/2) = 1.04 - 1.38 GeV with the SND detector in the experiment at the VEPP-2M e+e- collider

The cross section of the process $e^+e^- \to K^+K^-$ was measured in the energy range $\sqrt{s}$ = 1.04--1.38 GeV in the SND experiment at the VEPP-2M $e^+e^-$ collider. The measured cross section is described by the model of vector meson dominance with contributions from the light vector mesons $ρ$, $ω$, $ϕ$ and their lowest excitations. The mean statistical accuracy of the measurement is 4.4 %, and the systematic uncertainty is 5.2 %.

hep-ex↗
arXiv2007

On the ambiguity of the interfering resonances parameters determination

In this paper the interfering resonances parameters determination ambiguity is considered. It is shown that there are two solutions for two fixed width resonances. Analytical relation between different solutions is derived. Numeric experiments for fixed width three and four resonances, and for model energy-dependent width two resonances confirm ambiguity of the resonances parameters determination.

hep-ph↗
arXiv2007

Reanalysis of the $e^+e^-\toηγ$ reaction cross section

In the experiment with the SND detector at the VEPP-2M $e^+e^-$ collider measuring the $e^+e^-\to ηγ$ cross section in the energy range $0.6<\sqrt{s}<1.38 \mathrm{GeV}$ the reanalysis of data is performed. The goal is to improve the accuracy of the previous results by analysing ambiguities in the approximation of energy dependence of the $e^+e^-\to ηγ$ cross section, which were not taken into account in our previous study. We report new results on the approximation of the $e^+e^-\to ηγ$ cross section based on Vector Dominance Model under new model parameter assumptions.

hep-ex↗
arXiv2006

Pion Form Factor at SND (new edition)

The update of the e^+e^-\toπ^+π^- process cross section, measured in the energy region \sqrt{s}<1 GeV with SND detector at VEPP-2M collider is presented.

hep-ex↗
arXiv2005

New results on e+e- -> hadrons exclusive cross sections from experiments with SND detector at VEPP-2M e+e- collider in the energy range sqrt(s)=0.4-1.4 GeV

New results of the e+e- -> pi+pi-, K+K-, K_SK_L, pi0/gamma, eta0/gamma processes cross section measurements are presented. The results are based on the 30 pb^-1 data, accumulated by SND detector at VEPP-2M e+e- collider in the energy range sqrt(s)=0.4-1.4 GeV during 1995-2000 years. The comparison with existing experimental data shows that the measurement accuracy is close to or better than the world average. For the e+e- -> pi+pi- process the accuracy is about 0.01. This is important for calculation of hadronic contribution into the muon anomalous magnetic moment.

hep-ex↗
arXiv2005

Study of the process $e^+e^- \to π^+π^-$ in the energy region 400<\sqrt[]{s}<1000 MeV

The cross section of the process e^+e^-\to π^+π^- was measured in the SND experiment at the VEPP-2M collider in the energy region 400<\sqrt[]{s}<1000 MeV. This measurement was based on about 12.4 \times 10^6 selected collinear events, which include 7.4\times 10^6 e^+e^-\to e^+e^-, 4.5\times 10^6 e^+e^-\toπ^+π^- and 0.5\times 10^6 e^+e^-\toμ^+μ^- selected events. The systematic uncertainty of the cross section determination is 1.3 %. The ρ-meson parameters were determined: m_ρ=774.9\pm 0.4\pm 0.5 MeV, Γ_ρ=146.5\pm 0.8\pm 1.5 MeV, σ(ρ\toπ^+π^-)=1220\pm 7\pm 16 nb as well as the parameters of the G-parity suppressed decay ω\toπ^+π^-: σ(ω\toπ^+π^-)=29.9\pm 1.4\pm 1.0 nb and ϕ_{ρω} = 113.5\pm 1.3\pm 1.7 degree.

hep-ex↗
arXiv2004

A comparison of methods for confidence intervals

Comparisons are carried out of the confidence intervals constructed with Neyman's frequentist method and with the ΔL=1/2 likelihood method, using the example of low-statistics life time estimates.

physics.data-an↗
arXiv2003

Study of the e^+e^-\toπ^0γprocess in the energy range 0.60-1.06 GeV

The process e^+e^-\toπ^0γin the energy range \sqrt{s}=0.60-1.06 GeV was studied at VEPP-2M collider with SND detector using 14 pb^{-1} of integrated luminosity. Data were analyzed in the framework of the vector meson dominance model. Preliminary results on obtained cross-section and parameters of ρ^0, ω,ϕ\to π^0γradiative decays are presented.

hep-ex↗
arXiv2003

Experimental study of the e^+e^-\toπ^+π^-π^0 reaction by SND detector in the energy range sqrt{s}=0.42--1.38 GeV

The review of the SND results of the $e^+e^-\toπ^+π^-π^0$ process study in the energy range $\sqrt[]{s}=0.42$ -- 1.38 GeV at VEPP-2M collider, based on about $2\times 10^6$ selected events, is presented. The total cross section, parameters of the $ρ$, $ω$, $ϕ$ resonances, and $ω^\prime$, $ω^{\prime\prime}$ states were obtained. It was found that $ρπ$ and $ωπ^0$ intermediate states describe the reaction dynamics. The experimental data cannot be described by a sum of only $ω$, $ϕ$, $ω^\prime$ and $ω^{\prime\prime}$ resonances contributions. This can be interpreted as a manifestation of the $ρ\to 3π$ decay, suppressed by $G$-parity, with relative probability $B(ρ\to 3π) = (1.01\pm^{0.54}_{0.36}\pm 0.034) \times 10^{-4}$.

hep-ex↗
arXiv2003

Study of the process $e^+e^- \to π^+π^-π^0$ in the energy region $\sqrt[]{s}$ below 0.98 GeV

The cross section of the process $e^+e^-\to π^+π^-π^0$ was measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2M collider in the energy region $\sqrt[]{s}$ below 980 MeV. This measurement was based on about $1.2 \times 10^6$ selected events. The obtained cross section was analyzed together with the SND and DM2 data in the energy region $\sqrt[]{s}$ up to 2 GeV. The $ω$-meson parameters: $m_ω=782.79\pm 0.08\pm 0.09$ MeV, $Γ_ω=8.68\pm 0.04\pm 0.15$ MeV and $σ(ω\to 3π)=1615\pm 9\pm 57$ nb were obtained. It was found that the experimental data cannot be described by a sum of only $ω$, $ϕ$, $ω^\prime$ and $ω^{\prime\prime}$ resonances contributions. This can be interpreted as a manifestation of $ρ\to 3π$ decay, suppressed by $G$-parity, with relative probability $B(ρ\to 3π) = (1.01\pm^{0.54}_{0.36}\pm 0.034) \times 10^{-4}$.

hep-ex↗
arXiv2003

Experimental study of the e+e- -> pi0 gamma process in the energy region sqrt(s)=0.60-0.97 GeV

Results of the study of the e+e-->pi0 gamma process with SND detector at VEPP-2M collider in the c.m.s. energy range sqrt(s)=0.60-0.97 GeV are presented. Using 36513 selected events corresponding to a total integrated luminosity of 3.4 pb^-1 the e+e-->pi0 gamma cross section was measured. The energy dependence of the cross section was analyzed in the framework of the vector meson dominance model. The data are well described by a sum of phi,omega,rho0->pi0 gamma decay contributions with measured decay probabilities: Br(omega->pi0 gamma)=(9.34+-0.15+-0.31)% and Br(rho0->pi0 gamma)=(5.15+-1.16+-0.73)*10^-4 . The rho-omega relative interference phase is phi(rho,omega}=(-10.2+-6.5+-2.5) degree.

hep-ex↗
arXiv2002

Study of the process $e^+e^- \to π^+π^-π^0$ in the energy region $\sqrt[]{s}$ from 0.98 to 1.38 GeV.}

The cross section of the process $e^+e^-\to π^+π^-π^0$ was measured in the Spherical Neutral Detector experiment at the VEPP-2M collider in the energy region $\sqrt[]{s} = 980 ÷1380$ MeV. The measured cross section, together with the $e^+e^-\to π^+π^-π^0$ and $ωπ^+π^-$ cross sections obtained in other experiments, was analyzed in the framework of the generalized vector meson dominance model. It was found that the experimental data can be described by a sum of $ω$, $ϕ$ mesons and two $ω^\prime$ and $ω^{\prime\prime}$ resonances contributions, with masses $m_{ω^\prime}\sim 1490$,$m_{ω^{\prime\prime}}\sim 1790$ MeV and widths $Γ_{ω^\prime}\sim 1210$, $Γ_{ω^{\prime\prime}}\sim 560$ MeV. The analysis of the $π^+π^-$ invariant mass spectra in the energy region $\sqrt[]{s}$ from 1100 to 1380 MeV has shown that for their descriptionone should take into account the $e^+e^-\toωπ^0\toπ^+π^-π^0$ mechanism also. The phase between the amplitudes corresponding to the $e^+e^-\toωπ$ and $e^+e^-\toρπ$ intermediate states was measured for the first time. The value of the phase is close to zero and depends on energy.

hep-ex↗
arXiv2001

Review of experimental results from SND detector

The review of experimental results obtained with SND detector at VEPP-2M $e^+e^-$ collider in the energy region $\sqrt[]{s}=0.36$ -- 1.38 GeV is given. The presented results include the following items: studies of the light vector mesons radiative decays, OZI-rule and G-parity suppressed $ϕ$-meson rare decays, $ϕ$-meson parameters measurements, studies of $e^+e^-\toπ^+π^-π^0$ process dynamics, $η$ and $K_S$ mesons rare decays, $η$ and $ϕ$ mesons conversion decays, and study of the $e^+e^-$ annihilation into hadrons.

hep-ex↗
arXiv2001

Study of the $ππ$ mass spectra in the process $e^+e^- \to π^+π^-π^0$ at $\sqrt[]{s} \simeq 1020$ MeV

The invariant mass spectra of the $π^+π^-$ and $π^\pmπ^0$ pairs in the process $e^+e^- \to π^+π^-π^0$ were studied in the SND experiment at the VEPP-2M collider in the energy region $\sqrt[]{s} \simeq 1020$ MeV. These studies were based on about $0.5 \times 10^6$ experimental events. The spectra were analyzed in the framework of the vector meson dominance model. It was found that the experimental data can be described with $e^+e^- \to ρπ\to π^+π^-π^0$ transition only. Upper limit on the branching ratio of the $ϕ(1020)\toπ^+π^-π^0$ decay through intermediate states different from $ρπ$ was obtained at the 90 % confidence level: $B(ϕ\toπ^+π^-π^0)<6 \cdot 10^{-4}$. The $ρ$-meson mass and width which follow from the spectra analysis are $m_ρ=775.0\pm 1.3$ MeV, $Γ_ρ=150.4 \pm 3.0$ MeV. Neutral and charged $ρ$-mesons mass difference was found to equal $m_{ρ^\pm}-m_{ρ^0}=-1.3\pm2.3$ MeV. In the $π^+π^-$ mass spectrum the $ρ-ω$ interference was seen at two standard deviations level.

hep-ex↗