The R value, defined as the ratio of the inclusive hadronic cross section and the muon cross section in e+e- collisions, is an important input for the calculation of the Standard Model predictions of the anomalous magnetic moment of the muon a_mu and the running of the QED coupling constant alpha_QED(m_Z) evaluated at Z pole. The BESIII collaboration has collected data with high statistics to measure the R value at more than 130 scan points between 2.0 and 4.6 GeV. In this presentation, the measurement between 2.2324 and 3.6710 GeV is discussed. On average, a total uncertainty of less than 3% is achieved, which is dominated by the systematic uncertainty.
|Collaboration / Activity||BESIII|
|First author||Zhiqing Liu|