Hadronic vector boson decay and the art of calorimeter calibration

Abstract

Presented here are several studies involving the energy measurement of particles using calorimeters. The first study involves the effects of radiation damage on the response of a prototype calorimeter for the Compact Muon Solenoid experiment. We found that the effects of radiation damage on the calorimeter's response are dose dependent and that most of the damage will occur in the first year of running at the Large Hadron Collider. Another study involved the assessment of the Energy Flow Method, an algorithm which combines the information from the calorimeter system is combined with that from the tracking system in an attmpt to improve the energy resolution for jet measurements. Using the Energy Flow Method, an improvement of ~ 30% is found, but this impovement decreases at high energies where the hadronic calorimeter resolution dominates the quality of the jet energy measurements. Finally, we developed a new method to calibrate a longitudinally segmented calorimeter. This method eliminates problems with the traditional method used for the calorimeters at the Collider Detector at Fermilab. We applied this new method in the search for hadronic decays of the W and Z bosons in a sample of dijet data taken during Tevatron Run IC. A signal of 9873±3950(sys) ±1130 events was found when the new calibration method was used. This corresponds to a cross section a{pp -^W,Z)- B{W, Z -^ jets) = 35.6 ± 14.2(sys)±4.1(stat) nb.