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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 P_t^X of the hadronic final state is
shown depending on the transverse mass M_T^l-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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