DELPHI Event r0022140e0008640

e+ e- ---> Mu+ Mu- gamma gamma
The Muons are identified as minimum ionizing or unseen in the HPC, minimum in the HAB and hits in 1 plane of the MUB. The Mu+ has 37.6 GeV and the Mu- 32.4 GeV.

Two showers are detected, one with 9.0 GeV in the HPC, the other with 6.4 GeV in the FEMC. The effective mass with the closest track is:
M(Mu+,Pi0(6.4)) = 8.4 GeV
M(Mu-,Pi0(9.0)) = 6.0 GeV
hence excluding that Taus are at the origin of the muons, (mis-interpreted charged pions).

The event can thus be interpreted as a Mu+ Mu- with two photons radiated in the initial or final state. The latter is the most likely explanation, since the angles of the photons with the outgoing tracks are smaller than with the beam.