First WW event at LEP, observed by DELPHI on the 9th of July 1996:

Official CERN press release

The links in the press release are not up-to-date anymore, but used to point to the following plots from the DELPHI event pictures page:

• Run 67777 event 16923, 4-jet decay
  
  

  zx view	shaded view	Energy Flow

  
  
  First candidate W+W- event, where both Ws decay into quark-antiquark pairs.
  The two pairs of back to back jets have masses consistent with 80 GeV.
  
  The first W decays into the red and the black jets, both back to back and directed into the barrel of the detector.
  The second W decays into the green and the blue jets which go into the DELPHI end caps.
  The third picture displays the energy flow and nicely shows the clear angular separation of the four jets in the event. The horizontal axis gives the polar angle, Theta. The vertical axis gives the azimuth, Phi, multiplied by sin(Theta) to keep constant areas in all points of the plot. The plot is slightly rotated, with the Phi = 0 axis indicated as a dotted line. The colors are the same as in the other pictures, except the yellow jet which corresponds to the black tracks.
  
  

The 3-fold ambiguity due to the 3 possible choices of jet pairing are clearly visible. The back-to-back solution at 80 GeV is extremely close to the kinematical limit and therefore strongly suppressed by phase space considerations (which is why at WW production threshold the indirect W mass measurement via the cross-section is used instead).