Real Z --> e+ + e- decays

(Explanations below the WIRED view) Your browser does not support Java.

Below is static picture of the event:


Zoom out until you see the entire event and switch on the barrel electromagnetic calorimeter ("EMCal" in the "Barrel"). The red and green blocks represent the energy deposits in the electromagnetic calorimeter and their size is proportional to the measured energy of the particle. Switch between End view and Side view to see the directions of the electron and the positron.


This is also a Z decay into an electron and a positron. However, there is also a photon that has radiated from the electron during its passage through the detector. Neutral particles such as photons are represented by a thin straight line (since they are not detected by the tracking detectors) pointing to the energy deposit in the calorimeter.


Here you'll have to look at the event with the Side view and switch on the electromagnetic calorimeter in the end cap section of DELPHI ("EMCal" in the "Forward"). The electron and the positron come out at a small angle with respect to the beam pipe. Rotate the event until you see the real angle. By chance there are also two photons that have radiated from the electron during its passage.