DELPHI LEP183 EVENTS, 4-fermions
D E L P H I
Events from 183 GeV
Below is a sample of events taken by the DELPHI experiment during
the period where the LEP accelerator was running at 183 GeV energy in 1997.
To get the full size picture of an event (in Postscript), click on the icon.
To get its description, click on the label below the icon.
e+ e- --> e+ e- Mu+ Mu- :
(e e)(Mu Mu) event
| xy filled view
|| zy filled view
The event has (in green) an e+ of 61 GeV with an associated shower in the FEMC
and an e- of 40 GeV showering in the HPC.
The Mu+ (51 GeV) and the Mu- (15 GeV) are both forward (displayed in red)
at about 25 degree polar angle, MIP in the
hadron calorimeter and with associated hits in both planes of the Forward
The electron pair has a mass of approximately 89 GeV, compatible
with being a Z0.
The muon pair has a mass of 2.5 GeV, most likely produced by an
e+ e- --> e+ e- Tau+ Tau- :
(e e)(Tau Tau),
Tau -> Rho Nu, Tau -> Mu Nu Nu
| zy shaded view
This event has two clear tracks, one of which is a muon of 13 GeV, MIP in the
Forward Hadron Calorimeter and with associated hits in the Forward Muon Chambers.
The second one is a probable pion of 28 GeV with a clear associated shower in the
Barrel Hadron Calorimeter.
Nearby is a gamma shower of 20 GeV in the HPC which, together with the pion,
has an effective mass of 0.6 GeV, close to the Rho.
The Muon and the Rho are interpreted as decay products of a Tau pair.
Very forward, there is deposit of 23 GeV in the STIC (green cone)
and of 26 GeV in the FEMC (red shower).
The FEMC shower is preceeded by hits in FCB (in green) and in the
Forward RICH (red point close to the STIC).
This indicates that it originated from a charged track at too small polar angle
(about 10 degree) to be reconstructed.
The STIC shower is at even smaller angle and the particle which produced it
misses all tracking chambers.
The two showers correspond most likely to a very forward electron pair.
e+ e- --> Mu+ Mu- q qbar :
(Mu Mu)(q qbar) event
| zy shaded view
The forward (blue) tracks form a Mu+ Mu- pair of approximately 10 GeV mass.
On the opposite side is a two-jet system with about 77 GeV mass.
The missing momentum vector points mostly in the z direction
which is the sign of an additional photon radiated in the beam pipe.