Noise analysis of hpds in the hb and he calorimeters and self trigger analysis of sipms in the test setup at ho904 in the cms experiment

Hybrid photo diodes (HPDs) are used as a photodetector in the HB, HE and HO sub-calorimeter of the CMS - HCAL. Some problems has appeared in these HPDs since they are used in high energy operating and the magnetic field. The detectors recorded anomalous noise during the high energy runs. This anomalous noise is based on the feature of HPDs placed in the HB ? HE. HBHE Selftrigger runs were used, which have been taken June - July 2012 to determine noisy HPDs and RBXes. First of all, the 40 fC cut in the energy value is defined by analyzed the distribution of energy in the pixels of HPDs. Secondly, new cuts are defined according to distributions of signaling pixels on each of RBXes. The noisy RBXes - HPDs based on HPD ion feedback, HPD discharge and RBX noise were determined with these cuts. Due to magnetic field, problems has occurred in HPDs which are placed in HO calorimetry. Therefore, it is planned to replace HPDs with Silicon photomultipliers (SiPMs) in the readout module. Before assembling HO, these SiPMs have to be tested for some features such as pedestal, LED signal, noise, stability, gain, self trigger. This study includes the test results of HO SiPMs Self Trigger.