CMS HF calorimeter PMTS and Ξ+C lifetime measurement

This thesis consists of two parts: In the first part we describe the Photomultiplier Tube (PMT) selection and testing processes for the Hadronic Forward (HF) calorimeter of the CMS, a Large Hadron Collier (LHC) experiment at CERN. We report the evaluation process of the candidate PMTs from three different manufacturers, the complete tests performed on the 2300 Hamamatsu PMTs which will be used in the HF calorimeter, and the details of the PMT Test Station that is in University of Iowa CMS Laboratories. In the second part we report the Cascade_c_+ lifetime measurement from SELEX, the charm hadro-production experiment at Fermilab. Based upon 301+-31 events from three different decay channels, by using the binned maximum likelihood technique, we observe the lifetime of Cascade_c_+ as 427+-31+-13 fs.