Help on Interactive Event Display

A number of events of different types are provided (move between them by selecting Next Event and Previous Event), all the results of the annihilation of an electron and positron in the LEP Collider (as seen by the DELPHI Detector).

Although it's almost certainly easiest to see the topology of the event by rotating at random, you can think of it as dragging the surface of an (invisible) globe centred at the e⁺e^- collision point.

More details (perhaps only for experts) on running the Interactive Event Display follow.

Display Elements

• Tracks are displayed from the primary or secondary vertex to their last-measured point in the tracking detectors (excluding the muon chambers). To simplify the display, all tracks without a reconstructed secondary vertex are forced through the primary vertex. The primary vertex is defined as the origin (to simplify zooming).
• Calorimeter energy deposits are shown with a "histogram". You might notice that these have a slightly odd projective behaviour - this ensures that it maintains its length, which is proportional to the energy deposited. There are two layers of calorimeter: electromagnetic (on the inside) and hadronic (outside).
• Muon chamber hits are shown as small squares on the outside. You may have to Zoom out from the initial scale in order to see them.
• The jet assignments are shown by the colours on all the above elements.
• The scale and orientation of the detector is implied by the wire-frame view of the barrel electromagnetic calorimeter (HPC), shown in white.
• The initial window size represents 10.4 x 6.5 m. Each zoom in/out magnifies/reduces by a factor of two, giving
   

  Zoom In	Factor	Width (mm)	Height (mm)
  -1	0.5	20800	13000
  0	1	10400	6500
  1	2	5200	3250
  2	4	2600	1625
  3	8	1300	813
  4	16	650	406
  5	32	325	203
  6	64	163	102
  7	128	81	51
  8	256	41	25
  9	512	20	13
  10	1024	10	6

Known Bugs

• Sometimes the image is not redisplayed after a zoom or reset. Usually the image will be redrawn when you next click (though if you were zooming, you will have zoomed twice as far) or move the mouse pointer into the image area (even a small rotation will serve to redraw the image).
• At maximum magnification and certain orientations, some tracks may be shown as not coming from any vertex. This is an artifact of the display program (there are no single-track vertices) and can usually be cured by choosing a different orientation.
• WIRED has a small memory leak whenever one moves between events. If it is in use for a long time, you may find the system slowing down. The best way to remedy this is to restart Netscape, though for a short time after you quit it will refuse to load while the memory is cleared. However, this problem will probably only occur after several hours of usage.