Madevent is a package derived from MadGraph (which is quite stable and has been around for a long time). It produces events according to SM and BSM processes at the parton level, but also interfaces with Pythia. This isn't new. What is unique is that this can all be originated from a web interface.

The web page is: http://madgraph.hep.uiuc.edu/

• From Reinhard, May 24, 2007:

To get started, you should get registered on the registration web page. That will generate a username-password for you which you need to produce any processes.

Then go to the "Generate Process" page and start playing around with it. You can look at the example processes that it provides for you, for example uu~>dd~ as the input process. You can look at many other example processes as well, for example an electroweak one: ud~>e+ve. To generate something Tevatron related, you would use pp as the input particles, for example pp>e+ve. Once you enter this you'll see that there are more Feynman diagrams that can produce this process.

After you click "Generate Process", the program will take a little while and then direct you to a page for this process. If you click on the "Process Information" link you get to see all of the relevant processes and links to all of the Feynman diagrams.

Play with these a little bit, and enter different processes that you can think of to get an idea. Examples that I can think of are pp>tt~ or including decays: pp>tt~>bb~w+w-.

Two processes you should look at are the two single top ones: pb>tj, which is t-channel single top quark production, and pp>tb~, which is s-channel single top quark production.

For these last two, you should not only look at the Feynman diagrams but also produce events. Here's how to do that: The button "Code Download" allows you to download a .tar.gz file that does some event generation. Download it. Untar it and follow the instructions in the README file to run it. You should edit the Cards/run_card.dat file and adjust the following parameters: #********************************************************************* # Collider type and energy * #********************************************************************* 1 = lpp1 ! beam 1 type (0=NO PDF) -1 = lpp2 ! beam 2 type (0=NO PDF)

1. 1. = ebeam1 ! beam 1 energy in GeV
   2. = ebeam2 ! beam 2 energy in GeV

You will need to do a "setup D0RunII" in order to get the compiler set up before you generate events. Once that's done, run the ./bin/generate_events script. YOu should run serial and give a reasonable name, and then you just wait for events to be generated.

Then when you have an output file, you can use the web interface again to produce a root file and decay the top quark. Go to the "Tools" -> "Decay Interface" page. Browse to the Events/*_unweighted_events.lhe.gz file and load it. Select that you do want root output. Since your two single top files have a top quark in them, select the decay t > b ve e+. Then click on "Upload & Decay". After a while you'll get a page with links, one of which is the root file. Download the root file.

Download the ExRootAnalysis package from the "Downloads" tab. Follow the instructions to produce the library and then run the simple macro given in the Readme file at http://madgraph.hep.uiuc.edu/Downloads/ExRootAnalysis/README in order to produce your first histograms.

Once you have a histogram of jetPT and Mass as in the example macro we should talk again.

These instructions are quite long and it is likely that I missed something somewhere. There are also many steps involving topics you probably aren't familiar yet, and this is supposed to be a learning experience. Let me know if you get stuck or if you have any questions.

-- ChipBrock - 24 May 2007