Trigger efficiency measurement in R scan experiment

A method is introduced to measure the trigger efficiency in R scan experiment carried out with BESII at BEPC. The design of trigger table, offline event selection and calculation of efficiency are described. The principle of trigger efficiency measurement is: a data sample for specific physics event type is chosen orthogonally to certain trigger condition at both online trigger level and offline selection level; and then the ratio of number of events in the sample which satisfy the trigger condition to the total number of events in the sample is the efficiency of this trigger condition. The efficiencies of various trigger conditions, trigger channels and event types are given.