[Paper Review] Electroweak Monopole Production at the LHC - a Snowmass White Paper

Y. M. Cho, J. L. Pinfold|arXiv (Cornell University)|Jul 31, 2013

Superconducting Materials and Applications1 references3 citations

TL;DR

This paper argues that the electroweak (Cho-Maison) magnetic monopole, predicted by the Standard Model due to the non-trivial topology of the SU(2)×U(1)Y gauge group, should be produced at the LHC with a cross-section enhanced by (1/αem)² relative to W⁺W⁻ pairs. It advocates for the MoEDAL experiment as the optimal detector for such highly ionizing monopoles, capable of detecting them via ionization tracks in nuclear track detectors and trapped magnetic charge in superconducting quantum interference devices (SQUIDs), with discovery possible even from a single event.

ABSTRACT

We maintain that the search for the electroweak monopole is a key issue in the advancement of our understanding of the standard model. Unlike the Dirac monopole in electrodynamics, which is optional, the electroweak monopole should exist within the framework of the standard model. The mass of the electroweak monopole is estimated to be 5 to 7 TeV, but could be as large as 15 TeV. Above threshold its production rate at the LHC is expected to be relatively large, (1/alpha(em)2) times bigger than that of W+W- pairs. The search for the electroweak monopole is one of the prime motivations of the newest LHC experiment, MoEDAL, which is due to start data taking in 2015.

Motivation & Objective

• To establish the theoretical existence of the electroweak monopole (Cho-Maison monopole) within the Standard Model framework.
• To argue that the monopole's magnetic charge is twice that of the Dirac monopole due to the U(1)em subgroup having a period of 4π.
• To demonstrate that the monopole's production cross-section at the LHC is significantly enhanced—(1/αem)² times larger than W⁺W⁻ pair production—making it detectable.
• To advocate for the MoEDAL experiment as the optimal detector for highly ionizing monopoles due to its unique sensitivity to slow, highly ionizing particles.
• To show that MoEDAL can detect the monopole via nuclear track detectors and SQUID-based trapping detectors, enabling direct measurement of magnetic charge and discovery with a single event.

Proposed method

• The paper uses the Weinberg-Salam model with a spherically symmetric ansatz for the Higgs doublet and gauge fields to derive the monopole solution.
• It applies Abelianization via the Cho decomposition to express the Lagrangian in terms of physical fields, including the electromagnetic field strength Fμν(em).
• The equations of motion are derived from the Lagrangian, showing that the monopole solution exists with a non-trivial second homotopy group π₂(SU(2)×U(1)Y/U(1)em) ≅ ℤ.
• The monopole's magnetic charge is calculated as 4π/e, twice the Dirac charge, due to the 4π periodicity of U(1)em.
• The MoEDAL detector is proposed as the primary detection method, using plastic nuclear track detectors (NTDs) to record ionization trails from highly ionizing monopoles.
• Trapping detectors made of aluminum are used to capture monopoles, with magnetic charge measured via SQUID magnetometry after periodic replacement and analysis.

Experimental results

Research questions

• RQ1 Does the Standard Model predict the existence of a topological magnetic monopole due to the non-trivial second homotopy of the vacuum manifold?
• RQ2 What is the magnetic charge of the electroweak monopole, and how does it differ from the Dirac monopole?
• RQ3 What is the expected production cross-section of the electroweak monopole at the LHC, and how does it compare to standard model processes like W⁺W⁻ pair production?
• RQ4 Can the MoEDAL experiment detect the electroweak monopole despite its high ionization and potential rapid absorption in standard LHC detectors?
• RQ5 Can MoEDAL directly measure the magnetic charge of a monopole and confirm its topological nature through trapping and SQUID detection?

Key findings

• The electroweak monopole is a topological soliton in the Standard Model, arising from the non-trivial second homotopy group π₂(SU(2)×U(1)Y/U(1)em) ≅ ℤ.
• The monopole carries a magnetic charge of 4π/e, twice that of the Dirac monopole, due to the 4π periodicity of the electromagnetic U(1) subgroup.
• The production cross-section for the electroweak monopole at the LHC is estimated to be (1/αem)² times larger than that of W⁺W⁻ pairs, making it significantly enhanced.
• The monopole's ionization power is approximately 9400 times that of a minimum ionizing particle (MIP), enabling detection via nuclear track detectors even at low fluxes.
• MoEDAL can detect the monopole with a single event in its NTD array or trapping detectors, with charge resolution as fine as 1/100 of an elementary charge.
• The MoEDAL experiment is uniquely capable of directly measuring magnetic charge via SQUID magnetometry, a first for a collider detector.