摘要:
利用北京谱仪BESⅢ实验采集的约9fb-1数据样本,BESⅢ测量了e+e-→π+π-J/Ψ过程的产生截面,并对在该过程中观测到的Y(4260)粒子的质量和宽度做了目前世界上最精确的测量.BESⅢ的测量给出Y(4260)粒子的质量在4.22 GeV/c2左右,比之前的测量偏低;宽度约44 MeV,比之前的测量窄很多.相比之前的实验,BESⅢ对Y(4260)粒子参数的精确测量给解释该粒子的理论模型提供了更强的约束.另外,BESⅢ实验在4.32 GeV/c2附近还观测到一个新粒子信号,信号显著性为7.6σ.新粒子的质量和宽度和之前观测到的Y(4360)粒子的质量和宽度在误差范围内吻合,有可能是同一个粒子.
Abstract:
Using 9fb-1 data collected with the BESⅢ spectrometer at the Beijing Electron Positron Collider Ⅱ storage ring,the production cross section of the e+e-→π+π-J/Ψ process was measured.We observed the Y(4260) resonance and measured its parameters with the best precision to date in the world.Our measurement shows that the mass ofY(4260) is around 4.22 GeV/c2 and its width is about 44 MeV,which are lower and much narrower,respectively,than previous measurements.BESⅢ's precise measurement sets a tighter constraint on the interpretation of the Y (4260) internal structure models compared with previous experiments.In addition,BESⅢ also observed a new resonance near 4.32 GeV/c2,with a statistical significance of 7.6σ.The mass and width of this resonance agree with the Y(4360) state within experimental error.
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