Abstract
Using 1310.6 × 106J/ψ and 448.1 × 106ψ(3686) events collected with the BESIII detector, the branching fractions of J/ψ decays to Σ+ overline{Sigma} − is measured to be (10.61 ± 0.04 ± 0.36) × 10−4, which is significantly more precise than the current world average. The branching fractions of ψ(3686) decays to Σ+ overline{Sigma} − is measured to be (2.52 ± 0.04 ± 0.09) × 10−4, which is consistent with the previous measurements. In addition, the ratio of mathcal{B} (ψ(3686) → Σ+ overline{Sigma} −)/ mathcal{B} (J/ψ → Σ+ overline{Sigma} −) is determined to be (23.8 ± 1.1)% which violates the “12% rule”.
Highlights
BESIII detector and Monte Carlo simulationThe BESIII detector [19] records symmetric e+e− collisions provided by the BEPCII storage ring [20], which operates with a peak luminosity of 1 × 1033 cm−2s−1 in the center-ofmass energy range from 2.0 to 4.9 GeV
Background estimationThere are two kinds of background events: peaking backgrounds and non-peaking backgrounds
In this paper we report, with improved precision, the branching fraction measurements of J/ψ → Σ+Σ− and ψ(3686) → Σ+Σ− based on 1310.6 × 106 J/ψ and 448.1 × 106 ψ(3686) events collected with the BESIII detector at the BEPCII collider during 2009 and 2012
Summary
The BESIII detector [19] records symmetric e+e− collisions provided by the BEPCII storage ring [20], which operates with a peak luminosity of 1 × 1033 cm−2s−1 in the center-ofmass energy range from 2.0 to 4.9 GeV. BESIII has collected large data samples in this energy region [21]. The EMC measures photon energies with a resolution of 2.5% (5%) at 1 GeV in the barrel (end cap) region. GEANT4-based [22,23,24] MC simulation software, which includes the geometric and material descriptions of the BESIII detector, the detector response, and digitization models as well as the detector running conditions and performance, is used to generate MC samples. The simulation models the beam energy spread and initial state radiation (ISR) in the e+e− annihilations with the generator kkmc [25, 26]. The parameters in the differential cross sections have been determined in ref. [36]
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