© SLAC National Accelerator Laboratory.
SLAC's Mark I detector was an array of sodium-iodide crystals that precisely measured gamma rays emitted in the electron-positron collisions. This computer reconstruction of a psi-prime decay in the detector shows how the decay makes a near-perfect image of the Greek letter psi (). The psi-prime particle is a meson consisting of a charm quark bound to an anti-charm quark. (Unit: 1)