Difficulties with Photonic Searches for Magnetic Monopoles

TL;DR

This paper critiques recent theoretical proposals and experimental limits on magnetic monopoles derived from photon interactions, arguing that the underlying theory is flawed and that current limits are not reliable.

Contribution

It demonstrates that the theoretical approach used to set monopole mass limits violates unitarity and is unstable, proposing a revised coupling that results in much smaller cross sections.

Findings

The proposed cross section violates unitarity at the limits.

Radiative corrections destabilize the theoretical predictions.

Revised monopole-photon coupling reduces the expected cross section.

Abstract

Recently, there have been proposals that the classic Euler-Heisenberg Lagrangian together with duality could be employed to set limits on magnetic monopoles having masses less than 1 TeV. The D0 collaboration at Fermilab has used such a proposal to set mass limits based on the nonobservation of pairs of photons each with high transverse momentum. In this note, we critique the underlying theory, by showing that at the quoted limits the cross section violates unitarity and is unstable with respect to radiative corrections. It is proposed that the correct coupling of magnetic monopoles to photons leads to an effective softening of the interaction, leading to a much smaller cross section, from which no significant limit can be obtained from the current experiments. Previous limits based on virtual monopole loops are similarly criticized.