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A. P. Lysenko

Publications and source records attributed to A. P. Lysenko.

At least 37 records · Page 2Linked to original sources
arXiv2013

Study of e+e- --> omega pi0 --> pi0 pi0 gamma in the energy range 1.05--2.00 GeV with SND

The cross section for the process e+e- --> omega pi0 --> pi0 pi0 gamma has been measured in the energy range 1.05--2.00 GeV. The experiment has been performed at the e+e- collider VEPP-2000 with the SND detector. The measured e+e- --> omega pi0 cross section above 1.4 GeV is the most accurate to date. Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements. Data on the e+e- --> omega pi0 cross section are well described by the VMD model with two excited rho-like states. From the measured cross section we have extracted the gamma^* --> omega pi0 transition form factor. It has been found that the VDM model cannot describe simultaneously our data and data obtained from the omega --> pi0 mu+ mu- decay. We have also tested CVC hypothesis comparing our results on the e+e- --> omega pi0 cross section with data on the tau- --> omega pi- nu_{tau} decay.

hep-ex↗
arXiv2010

Measurement of $ϕ$(1020) meson leptonic width with CMD-2 detector at VEPP-2M Collider

The $ϕ$(1020) meson leptonic width has been determined from the combined analysis of 4 major decay modes of the resonance ($ϕ\to K^+ K^-,K^0_LK^0_S,π^+π^-π^0,ηγ$) studied with the CMD-2 detector at the VEPP-2M $e^+e^-$ collider. The following value has been obtained: $Γ(ϕ\to e^+e^-) = 1.235\pm 0.006\pm 0.022$ keV. The $ϕ(1020)$ meson parameters in four main decay channels have been also recalculated: $B(ϕ\to K^+K^-) = 0.493\pm 0.003\pm 0.007$, $B(ϕ\to K_LK_S) = 0.336\pm 0.002\pm 0.006$, $B(ϕ\toπ^+π^-π^0) = 0.155\pm 0.002\pm 0.005$, $B(ϕ\toηγ) = 0.0138\pm 0.0002\pm 0.0002$.

hep-ex↗
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↗
arXiv2008

Measurement of e+e- -> phi -> K+K- cross section with the CMD-2 detector at VEPP-2M Collider

The process e+ e- -> phi -> K+ K- has been studied with the CMD-2 detector using about 542 000 events detected in the center-of-mass energy range from 1.01 to 1.034 GeV. The systematic error of the cross section is estimated to be 2.2%. The phi(1020) meson parameters in the phi -> K+K- decay channel have been measured: sigma_0(phi-> K+K-) = 2016 +- 8 +- 44 nb, m(phi) = 1019.441 +- 0.008 +- 0.080 MeV/c2, Gamma(phi) = 4.24 +- 0.02 +- 0.03 MeV, B(e+e-)B(K+K-) = (14.27 +- 0.05 +- 0.31)*10(-5).

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↗
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

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↗
arXiv2001

Direct measurement of the phi(1020) leptonic branching ratio

The process e+e-->mu+mu- has been studied by SND detector at VEPP-2M e+e- collider in the phi(1020)-resonance energy region. The measured effective phi meson leptonic branching ratio: B(phi->l+l-)=sqrt{B(phi->e+e-)*B(phi->mu+mu-)}=(2.89+-0.10+-0.06)*10^{-4} agrees well with the PDG value B(phi->e+e-)=(2.91+-0.07)*10^{-4} confirming mu-e universality. Without additional assumption of mu-e universality the branching ratio B(phi->mu+mu-)=(2.87+-0.20+-0.14)*10^{-4} was obtained.

hep-ex↗
arXiv1999

Medium energy calorimetry at SND: techniques and performances on physics

SND (Spherical Neutral Detector) is a general purpose nonmagnetic detector, successfully operating at Novosibirsk VEPP-2M collider during last four years in the center of mass energy range from 400 MeV up to 1400 MeV. Its crucial part is a 3-layer, fine grained, spherical NaI(Tl) electromagnetic calorimeter consisted of 1632 individual counters. Here we present a detailed description of the calorimeter and its performance, including such topics as calorimeter design, electronics, calibration, energy and spatial resolutions, particle identification. The calorimeter performance is illustrated by examples from the current studies of different physical processes.

hep-ex↗
arXiv1998

Experiments at VEPP-2M with SND detector

Short overview of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E = 400 - 1400 MeV and preliminary results of data analysis are presented.

hep-ex↗
arXiv1998

Evidence of the PHI(1020)--->ETA+PI0+GAMMA Decay

Signal of the rare radiative decay PHI--->ETA+PI0+GAMMA was observed in the SND experiment at VEPP-2M electron-positron collider.The result is based on the analysis of data, corresponding to a total integrated luminosity of 4 pb^{-1}, or 8x10^6 PHI mesons produced. The measured branching ratio of PHI--->ETA+PI0+GAMMA decay is equal to (0.83+-0.23)x10^{-4}.

hep-ex↗
arXiv1998

Study of $Δ(1232)$ isobar electroproduction at VEPP-2M $e^+e^-$ collider

Results from the Spherical Nonmagnetic Detector (SND) on $Δ(1232)$ isobar electroproduction in the collisions of beam electrons (positrons) and residual gas nuclei in the VEPP-2M $e^+e^-$ collider are presented. On the basis of the obtained data the expected counting rate of this process in future high luminosity $e^+e^-$ colliders (~$ϕ$-, $c$-$τ$- and $b$-factories) was estimated.

hep-ex↗