| With the (14.00±0.56) ×106 Ψ(2S) events and the continuum data(Ecm=3.65GeV) with integrated luminosity (6.42 ± 0.24)pb-1 collected by BES-II detector at the Beijing Electron Positron(BEPC), the processes of Ψ{2S) → pp, ∧∧, Σ0Σ0, (?) have been studied in detail. The contribution from continuum is considered when calculating the branching fraction Ψ(2S) decays into the above four final states. New branching ratios of these channels are determined to be (3.31 ± 0.09 ± 0.23) x 10-4, (3.39 ± 0.20 ± 0.32) × 10-4, (2.35 ± 0.36 ± 0.32) × 10-4, and (3.00 ± 0.42 ± 0.31) ×10-4, respectively. It is found that all of them are bigger than the results from PDG(2004), but are in agreement with the results of CLEO collaboration reported in 2005.The measurements of Ψ(2S) —> pp, ∧∧, Σ0Σ0, (?) discussed in this paper are based on the biggest Ψ(2S) sample in the world by now, which makes it possible to depress the statistical error of the branching ratios in these channels.To test the "12% rule" predicted by PQCD, the measured branching fraction of the Ψ{2S) decay to each final state is compared with that of the J/Ψ decay, and find the ratio of branching fractions of Ψ(2S) to J/Ψ decay is in agreement with the "12% rule" prediction within 2 σ.The parameter of angular distribution, α, in Ψ{2S) —> pp decay is measured in this paper, and the 58M J/Ψ data is used to correct the efficiency of MC. The α is determined as α = 0.82 ± 0.17 ± 0.04, this result is in agreement with the hadronic helicity conservation rule.In this paper, the possible systematic errors to the measurement of branching ratio are analyzed, which include the uncertainties in charged track reconstruction,...
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