MoEDAL: Passive but no less active

Relying almost completely on passive detectors, MoEDAL is a pioneering experiment designed to search for highly ionising avatars of new physics, such as magnetic monopoles or massive (pseudo-)stable charged particles. The first test detectors were deployed at LHC Point 8 in 2012 and analysed in 2013, and the full MoEDAL detector was installed in the winter of 2014 to start data-taking during Run 2 this year.


The image shows the MoEDAL detector systems installed at Point 8 of the LHC.

MoEDAL’s groundbreaking physics programme defines over 30 scenarios that yield potentially revolutionary insights into such fundamental questions as: are there extra dimensions or new symmetries? Does magnetic charge exist? What is the nature of dark matter? And how did the big bang develop? MoEDAL's purpose is to meet such far-reaching challenges at the frontier of the field.

Having reached its final configuration in winter 2014, MoEDAL now consists of ten layers of plastic attached to the walls and ceiling of the cavern that houses LHCb’s VELO detector at Point 8 of the LHC ring. Its plastic Nuclear Track Detectors act like the film of a camera sensitive only to new physics: when a heavily ionising stable particle, such as a magnetic monopole or a massive stable super-symmetric particle, crosses MoEDAL’s detectors, it damages the plastic at the level of polymeric bonds in a small cylindrical region around its trajectory. The subsequent etching of the solid nuclear detectors leads to the formation of etch-pit cones. These conical pits are usually of micrometre dimensions and can be observed offline with an optical microscope. Their size, shape and alignment yield accurate information about the charge and the direction of motion of the incident highly ionising particle, thus they reveal the nature of particle messengers of physics beyond the Standard Model for further study. For example, if it exists, a magnetic monopole will leave a very characteristic set of collinear etch-pits.

The Magnetic Monopole Trapper (MMT) is MoEDAL’s second sub-detector system consisting of roughly 1 tonne of aluminum trapping volumes deployed around the MoEDAL cavern. A fraction of the massive HIPs created will be captured in the MMT detector. The exposed MMT trapping volumes will be monitored at the ETH Zurich SQUID facility for the presence of captured monopoles and then to SNOLAB to be monitored for the decays of very long-lived electrically charged particles. The MMT detector is uniquely able to trap the particle messengers of New Physics for further study. MoEDAL's radiation environment is monitored by a third detector system, a real-time “digital-camera” TimePix pixel detector array.

Since its approval by CERN in 2010, the MoEDAL collaboration has trebled in size. It now includes 66 physicists from 23 universities and institutes in 13 countries on four continents. 

by MoEDAL Collaboration