Noise Filter Studies for CMS Forward Hadron Calorimeter (HF) Between Old and New PMT's Using Data in 2012

During the data taking before 2012 some abnormal events which have higher signals than expected were observed. Most of these were due to muons. When a muon hits the PMT glass window it creates a huge signal. To eliminate this kind of events 24 old HF PMTs (Hamamatsu R7525) in HF Minus at iphi 43 (corresponds to one sector) were replaced with new multi anode PMTs (Hamamatsu multi anode R7600) which have thin glass windows. These new PMTs were installed and tested in H2 test beam area in 2009 [1]. To check whether these new PMTs perform better than the old ones data taken in 2012 were analyzed using various predefined noise filters. Noisy rechits percentage was found to be around 6-7 \% for the new PMTs while it varies between 29-66 \% for the old PMTs for various trigger selections and for HFLongShortFilter after an energy cut of 500GeV [2].