59 research outputs found
Monte-Carlo generator for e+e- annihilation into lepton and hadron pairs with precise radiative corrections
Recently, various cross sections of e+e- annihilation into hadrons were
accurately measured in the energy range from 0.37 to 1.39 GeV with the CMD-2
detector at the VEPP-2M collider. In the pi+pi- channel a systematic
uncertainty of 0.6% has been achieved. A Monte-Carlo Generator Photon Jets
(MCGPJ) was developed to simulate events of the Bhabha scattering as well as
production of two charged pions, kaons and muons. Based on the formalism of
Structure Functions, the leading logarithmic contributions related to the
emission of photon jets in the collinear region are incorporated into the MC
generator. Radiative corrections (RC) in the first order of alpha are accounted
for exactly. The theoretical precision of the cross sections with RC is
estimated to be better than 0.2%. Numerous tests of the program as well as
comparison with other MC generators and CMD-2 experimental data are presented.Comment: LaTeX, 23 pages with 18 figure
Measurement of (1020) meson leptonic width with CMD-2 detector at VEPP-2M Collider
The (1020) meson leptonic width has been determined from the combined
analysis of 4 major decay modes of the resonance () studied with the CMD-2 detector at
the VEPP-2M collider. The following value has been obtained:
keV.
The meson parameters in four main decay channels have been also
recalculated: , , , .Comment: 14 pages, 3 figure
Study of the process e+e- to pi+pi-pi+pi-pi0 with CMD-2 detector
The process e+e- to pi+ pi- pi+ pi- pi0 has been studied in the center of
mass energy range 1280 -- 1380 MeV using 3.0 1/pb of data collected with the
CMD-2 detector in Novosibirsk. Analysis shows that the cross section of the
five pion production is dominated by the contributions of the eta pi+pi- and
omega pi+pi- intermediate states.Comment: 8 pages, 3 figure. Submitted to Phys. Lett.
Study of the Process in the C.M.Energy Range 1.05-1.38 GeV with CMD-2
The process has been studied with the CMD-2 detector
using about 950 events detected in the center-of-mass energy range from 1.05 to
1.38 GeV. The cross section exceeds the expectation based on the contributions
of the rho(770), omega(782) and phi(1020) mesons only.Comment: 12 pages, 3 figures, uses elsart.cls, submitted to Physics Letters
High-statistics measurement of the pion form factor in the rho-meson energy range with the CMD-2 detector
We present a measurement of the pion form factor based on e+e- annihilation
data from the CMD-2 detector in the energy range 0.6<sqrt(s)<1.0 GeV with a
systematic uncertainty of 0.8%. A data sample is five times larger than that
used in our previous measurement.Comment: 18 pages, 10 figures. Added comparison with KLOE measurement, minor
updates. Accepted by PL
Observation of the conversion decay at CMD-2
Using 15.1^{-1} of data collected by CMD-2 in the -meson energy range,
the branching ratio of the conversion decay has been
measured for the first time: B(\phi\to\pi^0e^+e^-) = (1.22 \pm 0.34 \pm 0.21)
\cdot 10 ^{-5}.Comment: 13 pages, 6 PostScript figures, uses refmerge.sty. To be published in
Phys. Lett.
Cross section of the reaction below 1 GeV at CMD-2
Using 3.07 of data collected in the energy range 0.60-0.97 GeV by
CMD-2, about 150 events of the process \epm \to \pch have been selected. The
energy dependence of the cross section agrees with the assumption of the
intermediate state which is dominant above 1 GeV. For the first
time \fourpi events are observed at the meson energy. Under the
assumption that all these events come from the meson decay, the value of
the cross section at the meson peak corresponds to the following decay
width:
\Gamma(\rho^0 \to \fourpi) = (2.8 \pm 1.4 \pm 0.5) {keV} or to the branching
ratio
B(\rho^0 \to \fourpi) = (1.8 \pm 0.9 \pm 0.3) \cdot 10 ^{-5}.Comment: 15 pages, 5 figure
Study of the Process e+ e- --> omega pi0 --> pi0 pi0 gamma in c.m. Energy Range 920--1380 MeV at CMD-2
The cross section of the process e+ e- --> omega pi0 --> pi0 pi0 gamma has
been measured in the c.m. energy range 920-1380 MeV with the CMD-2 detector.
Its energy dependence is well described by the interference of the rho(770) and
rho'(1450) mesons decaying to omega pi0. Upper limits for the cross sections of
the direct processes e+ e- --> pi0 pi0 gamma, eta pi0 gamma have been set.Comment: Accepted for publication in PL
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).Comment: 12 pages, 6 figures, 2 tables, uses elsart.cls (second version - some
figures are corrected
Study of the process e+e−→3(π+π−) in the c.m. energy range 1.5–2.0 GeV with the CMD-3 detector
AbstractThe cross section of the process e+e−→3(π+π−) has been measured using a data sample of 22 pb−1 collected with the CMD-3 detector at the VEPP-2000 e+e− collider. 7956 signal events are selected in the center-of-mass energy range 1.5–2.0 GeV. The measured cross section exhibits a sharp drop near the pp¯ threshold. A first study of dynamics of six-pion production has been performed
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