Angular Correlation of Positron Annihilation

Emily Duffield and Mike Veit

University of Minnesota

Methods of Experimental Physics Spring 2012

Abstract

The angular distribution of photons emitted from electron-positron annihilation was measured over an angular range of 180-138 degrees. High energy gamma rays emitted by 60Co were used to produce positrons which annihilated with electrons in a lead target. The photons created during the annihilation were detected and measured using a coincidence circuit and amplified above the background. The angular distribution of photons emitted from at-rest annihilations was plotted and compared to a fit accounting for the solid angle in the detectors with a reduced Chi Squared of 1.72. In-flight annihilations were unable to be resolved and the in-flight to at-rest annihilation ratio was inconclusive.