Quark-Pair Production in Proton-Nucleus Collisions

Abstract
The cross sections for pair production of quarks in proton-nucleus collisions are calculated using the cross section for the production of massive photons measured by Christenson et al. in a recent μ-pair experiment. A comparison with upper limits on the total quark production cross section measured at CERN and Serpukhov reveals that pointlike fractionally charged quarks with mass ≲ 3 GeV/c2 do not exist as free particles.