Monopole production via photon fusion and Drell-Yan processes: MADGRAPH implementation and perturbativity via velocity-dependent coupling and magnetic moment as novel features

TL;DR

This paper develops a theoretical and computational framework for monopole production via photon fusion and Drell-Yan processes, incorporating velocity-dependent coupling and magnetic moments, and implements these models into MADGRAPH for collider searches.

Contribution

It introduces a novel effective field theory with velocity-dependent magnetic charge and magnetic moments, and provides MADGRAPH implementations for monopole production processes.

Findings

Perturbative treatment of monopole cross sections achieved with velocity-dependent coupling and magnetic moment.

Implementation of monopole production processes into MADGRAPH UFO models for collider analysis.

Discussion of unitarity issues and phenomenological implications for monopole searches at colliders.

Abstract

In this work we consider point-like monopole production via photon-fusion and Drell-Yan processes in the framework of an effective U(1) gauge field theory obtained from conventional models describing the interaction of spin 0, 1/2, 1 magnetically-charged fields with ordinary photons, upon electric-magnetic dualisation. We present arguments based on such dualities which support the conjecture of an effective monopole-velocity-dependent magnetic charge. For the cases of spin-1/2 and spin-1 monopoles, we also include a magnetic-moment term kappa, which is treated as a new phenomenological parameter and, together with the velocity-dependent coupling, allows for a perturbative treatment of the cross-section calculation. We discuss unitarity issues within these effective field theories, in particular we point out that in the spin-1 monopole case only the value kappa=1 may restore unitarity. However from an effective-field-theory point of view, this lack of unitarity should not be viewed as an impediment for the phenomenological studies and experimental searches of generic spin-1 monopoles, given that the potential appearance of new degrees of freedom in the ultraviolet completion of such models might restore it. The second part of the paper deals with an appropriate implementation of photon-fusion and Drell-Yan processes based on the above theoretical scenarios into MADGRAPH UFO models, aimed to serve as a useful tool in interpretations of monopole searches at colliders such as LHC, especially for photon fusion, given that it has not been considered by experimental collaborations so far. Moreover, the experimental implications of such perturbatively reliable monopole searches have been laid out.