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1 fb-1 X-Ray! May 12, 2006

Posted by gordonwatts in physics.

Science is sometimes produces the coolest images. This, I think, is one example. It is a closeup X-Ray of the DZERO detector. Andy Haas looked through our 1 fb-1 of data for all cases of two charged particles (“tracks”) intersecting. Each place he found one, he plots a “point” on that graph. The denser the points, the hotter the color. You can clearly see the layers of silicon (the flat lines) and the beam pipe (the circular lines near the center), as well as the support structre and the outter layers.

We don’t actually shine an X-Ray on the detector. The most common source of these 2-track verticies are conversions. A conversion happens when a gamma — a photon — converts to an electron and anti-electron. The x-ray term comes from… well, the gamma — because that is what an x-ray is! Pretty cool, eh? Click for a larger version!



1. Andy - May 12, 2006

Right, maybe we should call it a “G-ray” of the D0 detector… 🙂
Although their are some similarities between X-ray and G-ray images, there are also some major differences. X-ray images are made by looking where X-rays (~10keV photons) are absorbed by material. Since they are absorbed, you have no idea _where_ they were absorbed, just that you don’t see them coming out the other side. This G-ray was made by shining photons of energy ~1000000keV and above through material, and looking at where the photons turned into electron/positron pairs (or other particles), by _detecting_ the outgoing particles. Since you see the outgoing particles, you do know _where_ the interaction took place, so you actually have 3D information for a G-ray image. Perhaps this is the next “MRI”… 🙂 Unfortunately, it only works for very thin material (

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