The Calibration and Uniformity Mapping of the ALEPH Electromagnetic Calorimeter

Hearns, John L (1992) The Calibration and Uniformity Mapping of the ALEPH Electromagnetic Calorimeter. PhD thesis, University of Glasgow.

Abstract

The first chapter of this thesis is an introduction to the field of high energy physics, concentrating on the physics of electron-positron colliders. The historical development of electron beam colliders is discussed, culminating in the LEP and SLC accelerators. The principles behind the various techniques used in high energy particle detectors are discussed. A survey of the physics results so far obtained by the ALEPH collaboration is presented. The next chapter is an overview of the principles of operation of calorimeter devices. The practical implementation of many varieties of calorimeter at accelerator facilities is discussed. In the third chapter, the LEP accelerator complex at CERN and the four detectors in operation at LEP are briefly described. All parts of the ALEPH apparatus are described in detail. The fourth chapter concerns the software implemented by the ALEPH collaboration for on-line data collection, reconstruction of events and Monte Carlo simulation. Emphasis is made on the aspects relevant to the electromagnetic calorimeter. The next chapter is concerned with the design, construction, calibration and operation of the ALEPH electromagnetic calorimeter, concentrating on the end-cap segments. The various methods used to test and calibrate the device prior to its installation at the ALEPH experimental site and during data taking are discussed. The methods used to measure the uniformity of response of the end-cap segments are described. The thesis presents the analysis of the results of several different techniques which aimed to measure and map the uniformity of response of the calorimeter modules and to calibrate their response prior to LEP data taking. The calorimeter has an energy resolution of 17%√E. and the uniformity is measured to be at the level of ~ 2%. The original design concept of the calorimeter is shown to be sound. The device is demonstrated to be an admirable instrument, capable of taking data at the current LEP accelerator and at higher energy and higher luminosity in the future. The final chapter of the thesis presents an analysis of the reconstruction of pi° mesons using the electromagnetic calorimeter. The inclusive pi° momentum spectrum is measured and is compared with the Lund fragmentation model and the results from the competing L3 experiment.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Ken Smith
• Keywords: High energy physics
• Date of Award: 1992
• Depositing User: Enlighten Team
• Unique ID: glathesis:1992-74655
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 27 Sep 2019 17:19
• Last Modified: 27 Sep 2019 17:19
• URI: https://theses.gla.ac.uk/id/eprint/74655