Direct Photon and pi0 Production in pi-p, &pi+p and pp Interactions at 280 GeV/C

[摘要] This thesis presents results on direct photon and pi0 production in pi-p, pi+p and pp interactions at an incident beam momentum of 280 GeV/c, using data recorded by CERN experiment WA70 at the Omega Prime Spectrometer. Chapter 1 discusses the theoretical background for direct photon production and presents results from previous experiments. Chapter 2 describes the experimental apparatus used by WA70, with particular emphasis on the high-granularity electromagnetic calorimeter constructed specifically for the experiment. Chapter 3 discusses the reconstruction programs used to process the raw data from the Omega Prime Spectrometer and calorimeter prior to performing any physics analysis. Chapter 4 presents a detailed account of the method, developed by the author, to calculate the efficiencies of the individual planes of the 4m wire chamber, and presents these efficiencies for the two experimental runs. Chapter 5 discusses some of the methods used in offline calibration of the electromagnetic calorimeter, referring particularly to two separate studies performed by the author, (i) the detection of a discontinuity in the online calibration for the 1984 data taking run, and (ii) the search for a J/ps signal in the 1985 run, which would be particularly useful, since the e+e- pair can be detected in both the wire chambers and photon detector. In Chapter 6 an analysis of the 1985 data is performed to provide the cross- sections for direct photon and pi production and the ratio of the cross-sections. This chapter gives a description of the procedures involved in producing the raw signals, calculating the various cuts and contaminations, and evaluating the detection efficiencies for pi and direct photons. The pi cross-sections are compared to the parametrised results from other experiments, and the direct photon cross-sections are compared with the predictions of next-to-leading order QCD.

[发布机构] University:University of Glasgow

[关键词] High energy physics