Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; Jinan Univ, Inst Sci, Jinan 250022, Peoples R China
; Guangxi Normal Univ, Coll Phys & Elect Engn, Guilin 541004, Peoples R China
; Tsing Hua Univ, Dept Engn Phys, Beijing 100084, Peoples R China
The uncertainty of the treatment for the beam associated backgrounds is one of the dominant errors in the previous R measurement at BES/BEPC. A new method is developed to separate the beam associated sample from the raw data, and this sample is used in tuning the parameters of the hadronic generator LUARLW. This improvement can decrease the systematic error of the selection efficiency of hadronic events, and improve the precision of the R value.