J/ψ→π~03(π^+π^-)分支比的测定

Branching Ratios of J/ψ→π~03(π^+π^-)

用BESⅠ的 7.8× 1 0 6 J/ ψ数据更为精确地测定了J/ ψ→π0 3 (π+π- )和J/ ψ→ω2 (π+π- )的分支比 (Br(J/ ψ→π0 3 (π+π- ) ) =( 2 .52± 0 .0 6± 0 .4 3 ) % ,Br(J/ ψ→ω2 (π+π- ) ) =( 1 .3 1± 0 .0 9± 0 .2 1 ) % .同时对 4π不变质量谱和ωππ不变质量谱进行研究分析 ,试图观察是否存在有兴趣的信号 .

The decay mode of J/ψ→π 03(π +π -) was studied very little before. There are no informations except branching ratios for this channel in PDG book which based on less than 0.2×10 6 J/ψ events of MARKⅠ. Now, BESⅠ has a data sample of 7.8×10 6 J/ψ events, we can make more accurate results than MARKⅠ. Total of 3290±43 J/ψ→π 03(π +π -) events including 1275±86 J/ψ→ω2(π +π -) events are selected. J/ψ→π 03(π +π -) and J/ψ→ω2(π +π -) events have been generated with MC simulition for calculating events selection efficiency. BESⅠ result is: Br(J/ψ→π 03(π +π -))=(2.52±0.06±0.43)% and Br(J/ψ→ω2(π +π -))=(1.31±0.09± 0.21)%. Meanwhile, we studied the invariant mass of 4π and ωππ to find interesting signals. It seems that there is a peak at about 1.74GeV in the invarianat mass spectrum of 4π, and a enhancement was also found at about 1.9GeV in the invariant mass spectrum of ωππ. It is not clear whether they are from resonances or background. Therefore, more work in detail is still going on.