Quark event. Electronic display of subatomic particles created in a proton-antiproton collision in the CDF detector at Fermilab, the Fermi National Accelerator Laboratory near Chicago, USA. The proton-antiproton collision has produced a burst of energy which rematerialises as a high- energy photon (yellow beam & red rectangle at top right) and a quark, which is unseen because it immediately decays into a jet of other particles (pink tracks). The CDF records the collisions of protons & antiprotons accelerated to high energy in Fermilab's Tevatron collider.