2-5GeV能区R值的测量

R MEASUREMENT BETWEEN 2-5 GeV

2—5GeV能区的R值对于精确确定QED跑动精细结构常数α(MZ2)、进而确定黑格斯粒子的质量具有重要意义,同时对μ子反常磁矩αμ的物理解释也有重要贡献。北京正负电子对撞机(BEPC)/北京谱仪(BES)在该能区进行了R值扫描测量,本文给出85个扫描点的初步结果,误差降低到原有水平的一半左右。

With an upgraded Beijing Spectrometer(BESII) at the Beijing Electron Positron Collider(BEPC) , the BES collaboration finished an R scan in the energy region from 2 to 5 GeV. Preliminary R values for all 85 scanned energy points are presented. This measurement will make an important contribution to the precision determination of a (MZ2) , the QED coupling constant evaluated at the Z pole.The present uncertainty is a serious limit to further progress in the determination of the Higgs mass from radiative corrections in the Standard Model. The results can also contribute to the interpretation of muon g-2 measurement.