The CMD-3 detector started data taking at the electron-positron collider VEPP-2000 1 in December 2010. The collected data sample corresponds to an integrated luminosity of 87 pb
−1
in the c.m. energy ...range from 1.06 up to 2 GeV and 91 pb
−1
from 0.32 to 1.06 GeV. The integrated luminosity was measured by counting
e
+
e
−
→
e
+
e
−
and
e
+
e
−
→ γγ events, allowing additional photons in the final state. Preliminary results of the luminosity measurement are presented for various energy ranges and its accuracy is estimated to be 1%.
The cross section of the process \(e^+e^-\to\pi^+\pi^-\) has been measured in the center-of-mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. ...The measurement is based on an integrated luminosity of about 88 pb\(^{-1}\), of which 62 pb\(^{-1}\) represent a complete dataset collected by CMD-3 at center-of-mass energies below 1 GeV. In the dominant region near the \(\rho\) resonance a systematic uncertainty of 0.7% was achieved. The implications of the presented results for the evaluation of the hadronic contribution to the anomalous magnetic moment of the muon are discussed.
The results of the experiment on the measurement of the e+e− → π+π− cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the vector ...dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The cross section for the production of a muon pair is measured in the energy range of the experiment.
The cross sections for the processes
e
+
e
−
→ 2(π
+
π
−
π
0
) and
e
+
e
−
→ 3(π
+
π
−
) at c.m. energies in the range of 1.5–2 GeV were measured with the aid of the CMD-3 detector at the VEPP-2000 ...collider of the Budker Institute of Nuclear Physics (Novosibirsk, Siberian Branch, Russian Academy of Sciences). The integrated luminosity in the respective experiment was 22 pb
−1
.
Using 3.3 pb−1 of data collected with the CMD-2 detector in the 720–840 MeV c.m. energy range, the branching fraction of the conversion decay ω→π0e+e− has been measured: ...B(ω→π0e+e−)=(8.19±0.71±0.62)×10−4. The upper limits for the branching fractions of the following conversion decays have been obtained at the 90% confidence level: B(ρ→π0e+e−)<1.6×10−5, B(ρ→ηe+e−)<0.7×10−5 and B(ω→ηe+e−)<1.1×10−5.
The article reviews different approaches to choosing the characteristics of repair materials in the restoration of the volumetric structure of concrete. Some approaches are insufficient for the ...choice of repair materials for the restoration of hydro-technical facilities, especially for structures with a long service life. After investigating multiple approaches, a suitable method was proposed for the same.
Using 3.07 pb
−1 of data collected in the energy range 0.60–0.97 GeV by CMD-2, about 150 events of the process e
+e
−→
π
+
π
−
π
+
π
− have been selected. The energy dependence of the cross section ...agrees with the assumption of the
a
1(1260)
π intermediate state which is dominant above 1 GeV. For the first time
π
+
π
−
π
+
π
− events are observed at the
ρ meson energy. Under the assumption that all these events come from the
ρ meson decay, the value of the cross section at the
ρ meson peak corresponds to the following decay width:
Γ(ρ
0→π
+π
−π
+π
−)=(2.8±1.4±0.5)
keV
or to the branching ratio
B(ρ
0→π
+π
−π
+π
−)=(1.8±0.9±0.3)·10
−5.
A superconducting rectifier fluxpump has been used for the dc power supply of the magnet system of the CMD-2 detector on the VEPP-2M collider at the Budker Institute of Nuclear Physics in Russia ...since 1989. The fluxpump provides a complete pumping cycle: charging the magnet system, stabilization of the magnetic field, and discharging. The fluxpump consists of an air-core current step-up superconducting transformer and two groups of thermally controlled superconducting switches arranged as a fullwave rectifier. Critical output current during the test was 5.4 kA. The accuracy of the field stabilization provided by the fluxpump is 2.5/spl middot/10/sup -5/. The fluxpump has exhibited reliable and safe operation during its entire history of use.
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