Photon Structure at HERA

The HERA collider at the DESY laboratory in Hamburg has been colliding
electrons and protons at very high energies since 1992. The goals of
HERA are to study the structure of the proton at the smallest
distances available, and to investigate the strong and electroweak
interactions of particle physics. Any discrepancy between the data and
the expectations of the "standard model" could be an exciting signal
for new physics, such as quark substructure or a new force. The UCL
group built a major part of the ZEUS general purpose detector at HERA
and has been working on physics analysis since the beginning of the
experiment.


Project Goals

Your team has been commissioned to analyse data from the ZEUS
experiment at HERA. You should search through a series of high energy
electron-proton scattering events, and sift out those events where a
low angle photon has collided with the proton and produced high energy
jets of particles (jet photoproduction). You should measure how much
of the photon's energy went into the collision, and use this
measurement to count the number of event where the photon appears to
have a structure. The result should be presented on a visually
stimulating web page, with the meaning of the results explained and
the events illustrated with examples of real collisions. The web page
should be understandable to a physics A level student.


1. Information Collection
-------------------------

You will need to understand the basic kinematics of jet
photoproduction, as well as something about the strong interaction
(Quantum Chromodynamics).  You will also need to find information
about the HERA accelerator and the ZEUS detector which collected the
data you are analysing. The information gathered will inform the rest
of the project: It will guide the analysis and the selection devised,
and will provide material for the presentation.

Some references which you may find useful:

- The ZEUS home page: http://www-zeus.desy.de/

- The workshops on HERA physics, available in the Castilleo-Spreadbury 
  library (D17).

- "Particle Physics" by B.R.Martin and G.Shaw, Wiley.

- "Quarks, Leptons and the Big Bang", J.Allday, IoP Publishing. 

2. Analysis Software 
--------------------

Accessing the data will require the use of some ZEUS software
packages. You will need to learn how to run these and understand their
results. You will also need to use CERN software (the "root" package)
to perform the analysis and make plots. This software is written in C++.


3. Presentation
---------------

You will need to investigate the best way of presenting the
results. Various packages exist, including a Java-based 3D event
display which you may wish to use to display your events.


Resources Available

You have 4 hours total of consultancy time available with the following
people.

Jon Butterworth:    Physics, CERN Software.jmb@hep.ucl.ac.uk
Ben West       :    Physics, Event displays.bjw@hep.ucl.ac.uk
Claire Gwenlan :    Physics, ZEUS Software.cg@hep.ucl.ac.uk

Your board member is Dr. Jon Butterworth, phone 7318, email
jmb@hep.ucl.ac.uk