31 research outputs found

    Study of the process e+eβˆ’β†’ppΛ‰e^+e^-\to p\bar{p} in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector

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    Using a data sample of 6.8 pbβˆ’1^{-1} collected with the CMD-3 detector at the VEPP-2000 e+eβˆ’e^+e^- collider we select about 2700 events of the e+eβˆ’β†’ppΛ‰e^+e^- \to p\bar{p} process and measure its cross section at 12 energy ponts with about 6\% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio ∣GE/GM∣=1.49Β±0.23Β±0.30|G_{E}/G_{M}| = 1.49 \pm 0.23 \pm 0.30

    Measurement of the neutron timelike electromagnetic form factor with the SND detector

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    The results of the measurement of the e+eβˆ’β†’nnΛ‰e^+e^- \to n \bar{n} cross section and effective neutron timelike form factor are presented. The data taking was carried out in 2020-2021 at the VEPP-2000 e+eβˆ’e^+e^- collider in the center-of-mass energy range from 1891 to 2007 MeV. The general purpose nonmagnetic detector SND is used to detect neutron-antineutron events. The event selection is performed using the time-of-flight technique. The measured cross section is 0.4-0.6 nb. The neutron form factor in the energy range under study varies from 0.3 to 0.2.Comment: 13 pages, 8 figure

    Study of the process e+eβˆ’β†’Ξ·Ο€0Ξ³e^+e^- \to \eta\pi^0\gamma in the energy range \sqrt{s} = \mbox{1.05-2.00} GeV with the SND detector

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    The process e+eβˆ’β†’Ξ·Ο€0Ξ³e^+e^-\to\eta\pi^0\gamma is studied in the center-of-mass energy range 1.05-2.00 GeV using data with an integrated luminosity of 94.5 pbβˆ’1^{-1} collected by the SND detector at the VEPP-2000 e+eβˆ’e^+e^- collider. The e+eβˆ’β†’Ξ·Ο€0Ξ³e^+e^-\to\eta\pi^0\gamma cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the ωη\omega\eta intermediate state. The measured cross section of the subprocess e+eβˆ’β†’Ο‰Ξ·β†’Ξ·Ο€0Ξ³e^+e^-\to\omega\eta\to\eta\pi^0\gamma is consistent with previous measurements in the e+eβˆ’β†’Ο€+Ο€βˆ’Ο€0Ξ·e^+e^-\to\pi^+\pi^-\pi^0\eta mode. It is found, with a significance of 5.6Οƒ\sigma, that the process e+eβˆ’β†’Ξ·Ο€0Ξ³e^+e^-\to\eta\pi^0\gamma is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. e+eβˆ’β†’a0(1450)Ξ³e^+e^-\to a_{0}(1450)\gamma, is measured. It is found to be 15-20 pb in the wide energy range from 1.3 to 1.9 GeV.Comment: 10 pages, 6 figures, to be submitted to European Physical Journal
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