Actually I should not use the same cut value on Cerenkov before and after HVs changes. I applied cut>200 after I reduced the HVs and aligned S.P.E to be 150 channels, but for ADC before HVs reduce, the S.P.E is at 300, so the cut should be larger than 200, which means the the Electron Efficiency for Cerenkov before HVs change could be lower than 94%. Anyway, the exact cut value has not been optimized yet but here I just give you a comparation.