If a heavy Dirac monopole exists, the light to light scattering below the monopole production threshold is enhanced due to the strong coupling of monopoles to photons. This effect could be observable in the collision of virtual photons at proton colliders. At the Fermilab Tevatron it will be seen as pair production of photons with energies 200–400 GeV and roughly compensated transverse momenta 100–400 $\mathrm{GeV}/c.\mathrm{}$ This effect could be seen at monopole masses of about 1–2.5 TeV at the upgraded Tevatron and 7.4–19 TeV at the CERN Large Hadron Collider depending on the monopole spin.

• Received 13 February 1998

DOI:https://doi.org/10.1103/PhysRevD.57.R6599