The figure above is a front view of the CLEO-II detector, with the electron-positron beam passing through the center of the detector going into (electrons) or out of (positrons) the plane of the figure. The electron and positron beams collide and annihilate in the center of the detector.
For more information on a particular detector element, click on that element in the figure above, or a pick a detector element here:
For technical details on the CLEO II detector, see Y. Kubota et al., Nucl. Inst. and Meth. A320, 66 (1992).