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).
Cross section measurement from the first energy scan.
Cross section measurement from the second energy scan.
Using the $1.9 pb^{-1}$ of data collected with the CMD-2 detector at VEPP-2M the decay mode $\phi \to \eta \gamma$, $\eta \to \pi^+\pi^-\pi^0$ has been studied. The obtained branching ratio is B($\phi \to \eta \gamma) = (1.18 \pm 0.03 \pm 0.06) %$.
The measured cross section for E+ E- --> PHI < ETA GAMMA>.
About 300 000 $e^+e^-\to \phi\to K^0_L K^0_S$ events in the center of mass energy range from 984 to 1040 MeV were used for the measurement of the $\phi$ meson parameters. The following results have been obtained: $\sigma_0 = (1367 \pm 15 \pm 21) nb, m_{\phi}=(1019.504 \pm 0.011 \pm 0.033) MeV/c^2, \Gamma_\phi=(4.477 \pm 0.036 \pm 0.022) MeV, \Gamma_{e^+e^-}\cdot B(\phi\to K^0_L K^0_S) = (4.364 \pm 0.048 \pm 0.065)\cdot 10^{-4}$ MeV.
Updated measurements of the E+ E- --> PHI --> K0L K0S measured and 'bare' cross sections for SCAN 1.
Updated measurements of the E+ E- --> PHI --> K0L K0S measured and 'bare' cross sections for SCAN 2.
Updated measurements of the E+ E- --> PHI --> K0L K0S measured and 'bare' cross sections for SCAN 3.
The paper describes experiments with the SND detector at VEPP-2M collider, carried out during the period from October 1995 until June 1997. The total integrated luminosity of 6.4 pb^{-1} was collected in the energy range 2E=0.4-1.4 GeV (MHAD97 experiment), corresponding to 4*10^5 mu^+ mu^- pairs produced. Preliminary results of the 1996 phi-meson experiment (FI96) are presented. The total number of phi-mesons produced is 4*10^6. New data on rare decays of phi and eta (550) mesons, in particular B(phi -> eta gamma) = (1.30+-0.06+-0.07)%, B(phi -> pi^0 pi^0 gamma) = (1.1+-0.2)*10^{-4}, (M_{pi^0 pi^0} > 800 MeV), B(phi -> f^0 gamma) = (4.7+-1.0)*10^{-4}, B(phi -> eta pi^0 gamma) = (1.3+-0.5)*10^{-4}, B(phi -> eta' gamma) < 1.7*10^{-4}, B(phi -> 2 pi^0 ) < 6*10^{-4} were obtained.
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We present the results of a measurement of the cross section oof the reaction e + e − → π + π − π + π − from 890 to 1100 MeV in the center of mass, obtained with a magnetic detector at the Orsay Storage Ring ACO. With respect to previous experiments, the present one offers the possibility of reconstructing events with at least one constraint and his improved statistics. We find that our measurement of the cross section for e + e − → π + π − π + π − is compatible with quasi two-body production of π A 1 ( m A1 = 1.1 GeV, Γ A1 ∼ 0.2−0.3 GeV), through the ϱ and ϱ′(1600) intermediate states. We were able to states. We were able to determine the cross section of this reaction at the energy of the φ meson and consequently an upper limit on the branching ratio of φ → π + π − π + π − .
UPPER LIMIT FOR PHI --> 4PI.
The radiative decay models of the φ-meson have been studied: e + e − → φ → ηγ →3 γ ; e + e − → φ → π o γ →3 γ . Cross sections σ φ → ηγ →3 γ and σ φ → π o γ →3 γ have been measured at five energies in the φ-meson energy region and clearly show the φ-resonance in the ηγ → 3 γ mode as well as in the π o γ → 3 γ mode. From a Breit-Wigner fit to the experimental data the values of the branching ratios are deduced: B φ → ηγ = (1.5 ± 0.4) × 10 −2 ; B φ → π o γ = (1.4 ± 0.5) × 10 −3 .
REMOVING RADIATIVE CORRECTIONS, THE PHI PEAK CROSS SECTIONS ARE 66 NB +- 25 PCT <ETA GAMMA> AND 6.5 NB +- 30 PCT <PI0 GAMMA>.
The cross section e + e − → π + π − π o has been measured in the φ energy region and at three other energies (915, 990, 1076 MeV) chosen outside the ω and φ resonances. In the same experiment the energy position and the width of the φ resonance have been determined from the φ →K S o K L o channel. It is found that the magnitude and energy dependence of the experimental cross section are well described by coherent production of ω and φ in the whole energy range 770 to 1076 MeV. Our data clearly show an interference effect which corresponds to an opposite sign between the two products g γω g ω →3 π and g γφ g φ →3 π of the coupling constants.
EXPERIMENTAL CROSS SECTIONS - RADIATIVE CORRECTIONS CAN BE SIGNIFICANT.
A large solid angle detector has been used to observe π + π − π o events produced at the φ energy by electron-positron collisions in the Orsay storage ring. Fitting our data with a Breit and Wigner curve, with a fixed width Γ = (3.8±0.4) MeV coming from K O S K O L analysis, we deduce σ e + e − → π + π − π O = (0.70±0.13) μ bat 2 E = Mφ . Using our measurements on the other φ decay modes we deduce ( φ → π + π − π o )/( φ → K o S K o L ) = 0.47±0.06 and ( φ → η o γ )/( φ → K o S K o L ) = 0.077±0.022. Assuming ( φ → K + K − )/( φ → K o S K o L ) = 1.60, we derive σ TOT = (4.7±0.4) μ b, Γ e + e − = (1.27±0.11 keV and g 2 o /4 π = 14.3±1.3 (without finite width correction). Furthermore (from the observation of the ππγ coplanar events) we put an upper limit to the mode e + e − → φ π + π − γ , Γ ( φ → π + π − γ ) ⩽ 0.007 Γ ( φ → Total ) with 90% C.L.
EXPERIMENTAL CROSS SECTIONS INCLUDING RADIATIVE EFFECTS.
FITTED PARTIAL AND TOTAL CROSS SECTION AT PHI PEAK, RADIATIVELY CORRECTED.
Data have been taken at the φ energy with the same large solid angle detector which has been used for the measurement of the ϱ and ω production by e + e − annihilations. From the φ → K o L K o S π + φ − excitation curve we have deduced the φ width Γ φ = (3.81 ± 0.37) MeV and the cross-section σ e + e − → K o L K o S = (1.48±0.08±0.12) μ b. (the quoted errors are respectively statistical and systematical.)
EXPERIMENTAL CROSS SECTION INCLUDING RADIATIVE EFFECTS.
FITTED CROSS SECTION AT PHI PEAK, RADIATIVELY CORRECTED.
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