EPPOG Masterclass
An International Student Investigation
To the Student International Data Analysis Group (SIDAG):
By mid-2008, the Large Hadron Collider (LHC) will see first beam at CERN. It will be the most powerful particle accelerator in the world, colliding protons with protons at a maximum energy of 14 TeV. Each collision is capable of producing a large variety of particles, which in turn decay into more particles, resulting in both rich sets of data and a great deal of background.
The task of SIDAG will be to analyze Z-boson data from the Large Electron-Positron collider (LEP). The LEP accelerator was in the 27 km circumfernce tunnel now occupied by the LHC until it was shut down in 1999. During that time, it made precision measurements of Z- and W-bosons. Decays of these particles, which are the carriers of the weak nuclear force, will be a significant part of the background in events seen in the LHC. Therefore, it is vital that we understand these decays very well.
There is another important motivation for understanding the Z. One of the key particles that physicists seek to discover is the Higgs boson. Interaction with the Higgs field is thought to give all other fundamental particles their properties of mass. If the Higgs exists, the LHC has a good chance of producing it and the giant ATLAS and CMS detectors have a good chance of detecting the products of its decay. One important decay channel for the Higgs (H) is H –> ZZ, that is a Higgs boson decaying into two Z-bosons, which in turn decay themselves. Again, a great way to discover the Higgs is to understand the Z.
For the reasons stated above, SIDAG is asked to study LEP event displays to determine into which particles the Z decays and the branching ratios of these decays. A branching ratio is number of times a particle undergoes a particular kind of decay (for example Z –> e+e-) compared to the total number of decays. To do this, members of SIDAG will need to learn about the Z-boson, the DELPHI and OPAL detectors that give us the event displays, and how to analyze the data. The Masterclass Workpage will give you resources for understanding the experiment as well as links to the data. The best resources, though, will be your physics teacher and particle physicist mentor. Finally, you may get a chance to compare your results with other SIDAG members from the US, Europe, and other places. Make the most of all your resources!
Get started at the Masterclass Workpage!
