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

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 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- and spin-1 monopoles, we also include a magnetic-moment term , 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 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.

Scattering of charged particles off monopole–anti-monopole pairs

“…Suppose that at LHC a monopole-antimonopole pair is produced by any of the studied mechanisms [8,[21][22][23]25]. If the pair is produced close to threshold the pair will move slowly away from each other in the interaction region.…”

“…Let us use the above study for LHC physics. Imagine that monopole-antimonopole pairs are created in the collisions [21][22][23]. Some of those pairs annihilate into photons and some of them escape the interaction region.…”

“…We used the production cross section for spin 0 monopoles [2] calculated using the techniques of refs. [21][22][23].…”

“…4. The monopole-antimonopole production cross section decreases rapidly with the monopole mass [21][22][23] and so will the number of scattered protons. We show these results in Fig.…”

“…Since the magnetic charge is conserved monopoles at LHC will be produced predominantly in monopoleantimonopole pairs (or monopolium) [21][22][23][24]. This magnetic chargeless pair, given the collision geometry, will produce a magnetic dipole field.…”