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All six events show missing transverse
momentum and therefore the signature of possible neutrino production. In
the figure the transverse momentum PtX of the hadronic final state is
shown depending on the transverse mass MTl-nu of the lepton-neutrino
system. The measured events are shown together with the uncertainty in
the two observables. |
Also shown are standard model expectations which correspond to 500
times the measured integrated luminosity. The circles represent the predictions
of W-boson production. For the muon decay channel also inelastic muon production
from two-photon processes is shown (triangle symbols). A direct comparison
of the measured events with the expectations from the different production
mechanisms of the standard model shows that the electron event can be explained
by W-boson production. However, for the five muon events only 0.8+-0.2
are expected. Two of the muon events are in a region of the phase space
in which W-boson production is expected. The observables of the other 3
muon events are in a phase space region that is atypical for W-boson production.
The possibilities to explain these events in the frame work of the standard
model are therefore limited.
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