DELPHI Event r064456e010143
from the 130-140 GeV Run
e+ e- ---> (e+) Mu- Nu_e Nubar_Mu
From 136.2 GeV run.
A single charged track is observed at a polar angle of about 50 degree.
It has 8 GeV/c momentum and appears as MIP in the HPC and HAB, but misses the
muon chambers.
It can be safely identified as a Mu.
There is no sign of other activity in the detector.
The event can be interpreted as a spectator e+ escaping in the beam pipe
after emitting a gamma that interacts with the e- via a W-.
This produces a Nu_e and a pair Mu- Nu_Mu from the W- decay.
Such a process is expected to occur at the level of about 0.8 pb.
Shown by H.Dijkstra at the seminar on LEP 1.5 results 12/12/95.