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I. A. Gaponenko

Publications and source records attributed to I. A. Gaponenko.

At least 19 recordsLinked to original sources
arXiv2008

Investigation of the $e^+e^- \to ωπ^0 \to π^0 π^0 γ$ reaction in the energy domain near the $ϕ$-meson

The $e^+e^- \to ωπ^0 \to π^0 π^0 γ$ process was investigated in the SND experiment at the VEPP-2M collider. A narrow energy interval near the $ϕ$-meson was scanned. The observed cross-section reveals, at the level of three standard deviation, the interference effect caused by $ϕ\to π^0π^0γ$ decay. The cross-section parameters, as well as the real and imaginary parts of the $ϕ$-meson related amplitude, were measured.

hep-ex↗
arXiv2001

Measurements of the parameters of the $ϕ(1020)$ resonance through studies of the processes $e^+e^- \to K^+K^-$, $K_SK_L$ and $π^+π^-π^0$

The cross sections of the processes $e^+e^- \to K^+K^-$, $e^+e^- \to K_SK_L$ and $e^+e^- \to π^+π^-π^0$ were measured in the SND experiment at the VEPP-2M collider in the energy region near the $ϕ(1020)$ meson. These measurements were based on about $10^6$ $K^+K^-$, $0.5 \times 10^6$ $K_SK_L$ and $0.4 \times 10^6$ $π^+π^-π^0$ selected events. Themeasured cross sections have been analyzed in the framework of the vector meson dominance model and the main parameters of the $ϕ$-resonance were obtained, such as its mass, width, the production cross section and branching ratios of the main decay modes. The measured value of the $ϕ$ meson total width, $Γ_ϕ = 4.21 \pm 0.04$ is lower than the present world average of $4.458 \pm 0.032$ MeV. Contributions in addition to the conventional vector meson dominance model were found in the $e^+e^- \to π^+π^-π^0$ reaction cross section.

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↗
arXiv2000

The $ϕ(1020)\toπ^0π^0γ$ decay

In the SND experiment at VEPP-2M $e^+e^-$ collider the $ϕ(1020)\toπ^0π^0γ$ decay was studied and its branching ratio was measured: $B(ϕ\toπ^0π^0γ)=(1.221\pm 0.098\pm0.061)\cdot10^{-4}$. It was shown, that $f_0(980)γ$ intermediate state dominates in this decay and the $f_0(980)$-meson parameters were obtained.

hep-ex↗
arXiv2000

The $ϕ\toηπ^0γ$ decay

Rare radiative decay $ϕ\toηπ^0γ$ was studied with SND detector at {VEPP-2M} electron-positron collider and its branching ratio was measured: $B(ϕ\toηπ^0γ)=(0.88\pm0.14\pm0.09)\cdot 10^{-4}$. Significant contribution of the $a_0(980)γ$ intermediate state was observed in the decay. The result is based on total integrated luminosity corresponding to $2\cdot10^7$ produced $ϕ$ mesons.

hep-ex↗
arXiv2000

Decay phi->pi+pi-

The process e+e- ->pi+pi- has been studied with the SND detector at VEPP-2M e+e- collider in the vicinity of phi(1020) resonance. From the analysis of the energy dependence of measured cross section the branching ratio B(phi->pi+pi-)=(7.1+-1.1+-0.9)*10^{-5} and the phase psi_pi=-(34+-4+-3)degrees of interference with the non-resonant pi+pi- production amplitude were obtained.

hep-ex↗
arXiv1999

New Data from SND Detector in Novosibirsk

The current status of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E_0=400-1400 MeV and recent results of data analysis for $ϕ$, $ω$ and $ρ$ decays and e^+e^- annihilation into hadrons are presented.

hep-ex↗
arXiv1999

The process $e^+e^-\toπ^+π^-π^0$ in the energy range 2E_0=1.04 - 1.38 GeV

In the experiment with the SND detector at VEPP-2M e^+e^- collider the process $e^+e^-\toπ^+π^-π^0$ was studied in the energy range 2E_0 from 1.04 to 1.38 GeV. A broad peak was observed with the visible mass $M_{vis}=1220\pm 20$ MeV and cross section in the maximum $σ_0\simeq 4$ nb. The peak can be interpreted as a $ω$-like resonance $ω(1200)$.

hep-ex↗
arXiv1999

Spherical Neutral Detector for VEPP-2M collider

The Spherical Neutral Detector (SND) operates at VEPP-2M collider in Novosibirsk studying e^+e^- annihilation in the energy range up to 1.4 GeV. Detector consists of a fine granulated spherical scintillation calorimeter with 1632 NaI(Tl) crystals, two cylindrical drift chambers with 10 layers of sense wires, and a muon system made of streamer tubes and plastic scintillation counters. The detector design, performance, data acquisition and processing are described.

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↗
arXiv1999

Upper limit on the Ks ---> 3 pi0 decay

The search for CP-violating K_S\to3π^0 decay was performed with SND detector at VEPP-2M e^+e^- collider. The total amount of data corresponding to 7 million produced K_S mesons was analyzed. No candidate events were found, giving an upper limit of the decay branching ratio: Br(K_S\to3π^0) < 1.4\cdot10^{-5} at 90% confidence level.

hep-ex↗
arXiv1999

Measurement of the decay phi->mu+mu-

The process e^+e^- ->mu^+mu^- has been studied with SND detector at VEPP-2M e^+e^- collider in the vicinity of phi(1020) resonance. The product of branching ratios of phi meson into leptons \sqrt{B(phi->mu^+mu^-) B(phi-> e^+e^-)}=(3.14+-0.22+-0.14)x10^{-4} was measured from the interference in the cross section of the process e^+e^- ->mu^+mu^-. The branching ratio B(phi->mu^+mu^-)=(3.30+-0.45+-0.32)x10^{-4} was obtained.

hep-ex↗
arXiv1999

Observation of the decay PHI(1020)--->OMEGA+PI0

The reaction e^+e^- ---> OMEGA+PI0 ---> PI+PI- 2PI0 has been studied with SND detector at VEPP-2M e^+e^- collider in the vicinity of the PHI(1020) meson resonance. The observed interference pattern in the energy dependence of the cross section is consistent with existence of the decay PHI ---> OMEGA+PI0 with a branching ratio of B(PHI ---> OMEGA+PI0)=(4.8+1.9-1.7+-0.8)x10^{-5}. The real and imaginary parts of the decay amplitude were measured. The PHI ---> OMEGA+PI0 decay was observed for the first time.

hep-ex↗