Suppression of top-up injection backgrounds with offline event filter in the BESIII experiment

Background It is imperative that high-quality data should be accumulated to guarantee the correctness and accuracy of physics results in particle physics experiments. The top-up injection of BEPCII has achieved a definite improvement in integrated luminosity, but simultaneously has an obvious impact on the background level of the data acquired by the BESIII detector due to frequent beam injections. Methods An online trigger veto and an offline event filter have been developed and applied to eliminate the contaminated events from the data samples for physics research. Results and Conclusion The design and implementation of offline event filter are described in this article. The upgraded offline data processing procedure with offline event filter was executed smoothly in recent years and ensured data acquisition and processing with optimal efficiency and sufficient quality in BESIII experiment.