Photon Structure at HERA
This page collects together various resources to help the project get started.
One very important resource is last
year's project page. The physics of the project was very
different, but the information regarding HERA and ZEUS, plus the event
display, should be very relevant. You may wish to reference this page
in your final page.
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.
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.
- 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.
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. The starting point for this the ORANGE
page. The main ZEUS analysis
pages may be useful too.
You will also need to use CERN software (the "root" package)
to perform the analysis and make plots. This software is written in C++.
The ZEUS data will be provided in "root" files containing "ORANGE
ntuples", with an array of variables for each event. You need to
decide what basic cuts should be applied before the ntuple is made
(i.e. which events you want in your ntuple) and also what information
you need about each event (i.e. what varibles should be in the
ntuple).
A small example root file containing an ORANGE ntuple for a few
hundred events is available in this directory
to get you started (orange_example.root). This directory also contains
the log file, and the control cards which orange was run with to
produce this data. You need to understand these so you can request
different ones in future if you need them.
The turnaround time for making new ntuples can be a few days, even a
week. You need to factor this into your schedules.
Presentation
You will need to investigate the best way of presenting the results. I
recommend you use the Java-based 3D event display to display your
events. This was used by the previous year's project with partial
success. You should build on their experience as summarised on their
web page (and maybe even talk to them about it!).
Contacts
For contact details see the project brief.