Aging phenomenon in BESIII drift chamber

2D hit efficiency distribution of the first four layers with data taken in 2023. The identifiers of the cells in each layer start from the positive X-axis and increase counterclockwise.本数据集涵盖2023年采集的前四层二维击中效率分布。各层内的探测器单元标识均以X轴正方向为起始点，沿逆时针方向依次递增。