[Paper Review] Direct and Indirect Searches for Low-Mass Magnetic Monopoles

Leonard Gamberg, G. Kalbfleisch+1 more|arXiv (Cornell University)|Jun 28, 1999

Superconducting Materials and Applications4 citations

TL;DR

This paper evaluates direct and indirect searches for low-mass magnetic monopoles, focusing on experimental limits from Fermilab's E882 and D0 collaborations. It argues that while direct searches for 500 GeV Dirac monopoles are viable using collider data and material binding estimates, the indirect method based on virtual monopoles via the Euler-Heisenberg Lagrangian is theoretically flawed due to unitarity violation and radiative instability, rendering such limits invalid.

ABSTRACT

Recently, there has been renewed interest in the search for low-mass magnetic monopoles. At the University of Oklahoma we are performing an experiment (Fermilab E882) using material from the old D0 and CDF detectors to set limits on the existence of Dirac monopoles of masses of the order of 500 GeV. To set such limits, estimates must be made of the production rate of such monopoles at the Tevatron collider, and of the binding strength of any such produced monopoles to matter. Here we sketch the still primitive theory of such interactions, and indicate why we believe a credible limit may still be obtained. On the other hand, 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, based on virtual, rather than real processes. 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. We critique the underlying theory, by showing that the cross section violates unitarity at the quoted limits and is unstable with respect to radiative corrections. We therefore believe that no significant limit can be obtained from the current experiments, based on virtual monopole processes.

Motivation & Objective

• To assess the viability of indirect limits on low-mass magnetic monopoles derived from virtual monopole contributions in photon-photon scattering.
• To evaluate the theoretical foundation of using the Euler-Heisenberg Lagrangian combined with duality to constrain monopole masses below 1 TeV.
• To examine the credibility of experimental limits set by the D0 collaboration based on high-transverse-momentum photon pairs.
• To explore the feasibility of direct detection of 500 GeV Dirac monopoles in the Fermilab E882 experiment using old D0 and CDF detector materials.
• To analyze the theoretical challenges in modeling monopole interactions with matter, particularly binding strength and production rates.

Proposed method

• Analyzes the Euler-Heisenberg Lagrangian extended by electromagnetic duality to model virtual magnetic monopole contributions to photon-photon scattering.
• Evaluates the unitarity of the predicted cross section for virtual monopole exchange at high energies.
• Performs a radiative correction analysis to test the stability of the cross section under quantum corrections.
• Estimates the production rate of real Dirac monopoles at the Tevatron collider for masses around 500 GeV.
• Models the binding strength of produced monopoles to detector materials to assess detectability in the E882 experiment.
• Compares theoretical predictions with experimental non-observation data from the D0 collaboration on high-pT photon pairs.

Experimental results

Research questions

• RQ1 Can the Euler-Heisenberg Lagrangian with duality provide a reliable theoretical framework for setting indirect limits on low-mass magnetic monopoles?
• RQ2 Does the predicted cross section for virtual monopole exchange in photon-photon scattering violate unitarity at the energy scales relevant to the D0 experiment?
• RQ3 Are the experimental limits on monopole mass derived from non-observation of high-transverse-momentum photon pairs physically justified given the theoretical instability of the underlying model?
• RQ4 What are the production rates and binding characteristics of real Dirac monopoles with mass ~500 GeV at the Tevatron?
• RQ5 Can the Fermilab E882 experiment set credible direct limits on 500 GeV magnetic monopoles using existing detector materials?

Key findings

• The cross section for virtual monopole exchange in photon-photon scattering violates unitarity at the energy scales considered in the D0 analysis, rendering the theoretical framework inconsistent.
• The cross section is unstable under radiative corrections, indicating that the model lacks predictive power for setting limits.
• As a result, no significant experimental limit on magnetic monopoles below 1 TeV can be reliably derived from the D0 experiment's non-observation of high-pT photon pairs.
• The direct search for 500 GeV Dirac monopoles in the E882 experiment remains theoretically viable, provided accurate estimates of production rates and binding to matter are available.
• The paper concludes that while direct detection is plausible, the indirect method based on virtual monopoles is theoretically unsound and should not be used to constrain monopole masses.