In the final states, e is electron-positron, l other charged lepton, n is neutrino, x is up-type quark and y is down-type quark. Some channels have one or more final quarks given explicitly. Hence, the "ttbar" channels are those with two y and the other four in combinations that can be comming from two W:s (ie xyxy, xyln or lnln in any order).
The links below brings you to the relevant pages at SLAC.
2048 May 29 18:05 ttbar
2048 May 29 18:05 WW + two electrons
2048 May 29 18:05 WW + two other charged leptons
2048 May 29 18:05 WW + two neutrinos
2048 May 29 18:05 WW + two up type quarks
2048 May 29 18:05 Z + four up type quarks
2048 May 29 18:05 Z + four down type quarks
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