You have to love that moment when you write some code to look at something physical and it just works. I have been asked to generate some Monte Carlo events for a Tevetron generation and subsequent decay of a Higgs boson plus a W boson. This process involves generating the actual Monte Carlo (which I was using Pythia and EvtGen to decay the B hadrons), simulate the detector responce, and then finally perform the reconstruction of objects from the detector simulation data. Here comes the hard part, can I find the W and the H from the Monte Carlo truth table? Can I find the decay daughters? And most importantly, can I find the reconstructed jets that correspond to the Monte Carlo decay partons? I thought I did, but I had to be sure. So I wrote a simple piece of code that utilized the Visualization Tool Kit (VTK) to have a look see.
So there it is. The objects in red are related to the Higgs particle and the objects in green are from the W boson. The size of the cone does not correspond to the energy but to which particle I am looking at. For instance, the widest is the actual Monte Carlo Higgs or W. The next smaller size cone represents the decay products and the smallest colored cones (barely visable) represent the reconstructed jets that are supposed to correspond to the Monte Carlo decay products. The black very narrow cones are all the reconstructed jets in the event. As you can see this is a pretty one. The medium colored cones have a narrow colored cone in each of them and there is a black cone coincident with this. This means that I was able to find the correct reconstructed jets that point back to the original H and W. Dont ask me about the energy |-)