https://vital.lib.tsu.ru/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://vital.lib.tsu.ru/vital/access/manager/Repository/koha:001007868 e(+)e(-)e(+)e(-) is observed for the first time via the J/psi -> gamma eta' decay process. The significance is found to be 5.7s with systematic uncertainties taken into consideration. Its branching fraction is determined to be B(eta' -> e(+)e(-)e(+)e(-)) = (4.5 +/- 1.0(stat) +/- 0.5(sys)) x 10(-6).]]> Fri 27 Oct 2023 13:41:46 KRAT ]]> https://vital.lib.tsu.ru/vital/access/manager/Repository/koha:001007869 Sigma(0)(Sigma) over bar (0) are measured at center-of-mass energies from 2.3864 to 3.0200 GeV using data samples with an integrated luminosity of 328.5 pb(-1) collected with the BESIII detector operating at the BEPCII collider. The analysis makes use of a novel reconstruction method for energies near production threshold, while a single-tag method is employed at other center-of-mass energies. The measured cross sections are consistent with earlier results from BaBar, with a substantially improved precision. The cross-section lineshape can be well described by a perturbative QCD-driven energy function. In addition, the effective form factors of the Sigma(0) baryon are determined. The results provide precise experimental input for testing various theoretical predictions. (C) 2022 The Author(s). Published by Elsevier B.V.]]> Fri 27 Oct 2023 13:34:48 KRAT ]]>