Analysis Overview

In order to examine how Xg is distributed we took data from the ZEUS experiment. This data then went through many stages (see flow diagram) until a histogram plot of the distribution was obtained.

Our goal for the analysis was to examine many electron – proton collisions (or events) and select those in which a small angle collision had occurred with at least two jets being formed.

The first stage of this was the raw data from the ZEUS detector. This, on its own, is not very useful. However it is passed through a reconstruction program that uses the data to calculate the general information such as the energies detected by the calorimeters. The performance curves of the instruments used to detect these values are well known by the engineers at ZEUS and so are computed at ZEUS before being released to the scientific community.

The next stage calculated other variables such as the path of jets or the positions of electrons. These variables are harder to calculate are there are many different methods of doing so. The Orange software package simplifies this task, data released from ZEUS is passed to the Orange package along with a control card. This control card specifies the types of data to be calculated and which methods are to be used to calculate them.

The final stage of the analysis was performed using the Root software package. This an analysis software package based in a C++ environment. This was used to discard any events, which did not fit our strict criteria of at least two jets’s being produced and the electron being deflected by a small angle. The events that were not discarded were plotted on a histogram, with the number of events along the y-axis and the magnitude of Xg along the x-axis.