Pair production refers to the creation of an elementary particle and its antiparticle, usually when a photon (or another neutral boson) interacts with a nucleus. For example an electron and its antiparticle, the positron, may be created. This is allowed, provided there is enough energy available to create the pair – at least the total rest mass energy of the two particles – and that the situation allows both energy and momentum to be conserved. Other pairs produced could be a muon and anti-muon or a tau and anti-tau. However all other conserved quantum numbers (angular momentum, electric charge, lepton number) of the produced particles must sum to zero – thus the created particles shall have opposite values of each other. For instance, if one particle has electric charge of +1 the other must have electric charge of −1, or if one particle has strangeness of +1 then another one must have strangeness of −1. The probability of pair production in photon-matter interactions increases with increasing photon energy and also increases with atomic number approximately as Z2.
Famous quotes containing the words pair and/or production:
“I should have been a pair of ragged claws
Scuttling across the floors of silent seas.”
—T.S. (Thomas Stearns)
“The growing of food and the growing of children are both vital to the family’s survival.... Who would dare make the judgment that holding your youngest baby on your lap is less important than weeding a few more yards in the maize field? Yet this is the judgment our society makes constantly. Production of autos, canned soup, advertising copy is important. Housework—cleaning, feeding, and caring—is unimportant.”
—Debbie Taylor (20th century)