This event is very recent, occurring at the end of May 1998, and is still not fully understood. 2 muons are formed, as well as two other jets of particles. It seems most likely that this was caused by two Z⁰ particles, rather than by a single Z⁰ or a W⁺W^- pair like the other events. One of these decayed into a pair of muons, while the other formed two jets.

Notes for experts: This event has two jets (the blue one, which is quite forward, is not well reconstructed here - this has been recovered in a different processing using DELPHI's new forward tracker), with a combined mass of 90 GeV/c². The yellow and green tracks are mu⁺mu^- with a combined mass also of 90 GeV/c². It is probably a Z⁰Z⁰ decay, which is background in the Higgs mu⁺mu^- channel.