This is the simplest form of electron - positron interaction; another identical electron-positron pair is produced from the products of the first pair's annihilation. The positron is shown as green, and the electron red. They give off all of their energy in the electromagnetic calorimeter, producing the large blocks visible there.

Notes for experts: Clear Bhabha event where the electron and positron have associated showers in the HPC. Both tracks are measured in the Vertex Detector, Inner Detector, and TPC. The electron (red) is reconstructed with a momentum of 45.9 GeV/c and has an associated HPC shower of 48.1 GeV. The positron (green) has 37.4 GeV/c momentum and an associated HPC shower of 44.0 GeV.