ATLAS, CMS, and probably many other physics experiments, use a bespoke coordinate system to describe the detector and kinematics, which is designed for physics in the high energy regime ruled by the laws of special relativity.
Conical objects are usually defined using a variable dR, which can be difficult to visualise. This notebook is a visualisation aid, possibly useful to students starting in the field to get an intuitive feel of how this variable behaves.
Rendered version of the notebook can be seen in the nbviewer, but unfortunately it does not support widgets. If you want slider control over phi, eta, and dR, as shown in the preview, run it on binder (click on the badge above) or fork it and run locally.
