MOEDAL first results at the LHC’s discovery frontier
In 2010 the MoEDAL experiment at the Large Hadron Collider (LHC) was approved, as the LHC’s newest experiment, to start data taking in 2015. MoEDAL is a pioneering experiment designed to search for highly ionizing avatars of new physics such as magnetic monopoles or massive (pseudo-)stable charged particles. Its groundbreaking physics program defines over 30 scenarios [1] that yield potentially revolutionary insights into such foundational questions as: are there extra dimensions or new symmetries; what is the mechanism for the generation of mass; 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.
The innovative MoEDAL detector employs unconventional methodologies tuned to the prospect of discovery physics. The largely passive MoEDAL detector, deployed at Point 8 on the LHC ring, has a dual nature. First, it acts like a giant camera, comprised of Nuclear Track Detectors (NTDs) - analyzed offline by ultra fast scanning microscopes - sensitive only to new physics. Second, it is uniquely able to trap the particle messengers of physics beyond the Standard Model, for further study in the laboratory. MoEDAL's radiation environment is monitored by a state-of-the-art real-time TimePix pixel detector array. A depiction of the MoEDAL detector deployed at IP8, adjacent to the LHCb detector, is shown in Figure 1.
Just as the search for the Higgs boson was a priority of the main LHC experiments ATLAS and CMS so is the quest for magnetic monopoles and dyons at LHC energies MoEDAL’s main concern for initial data taking. MoEDAL has reported search results for the magnetic monopoles at LHC centre-of-mass energies (Ecm)of 8 TeV [2] and 13 TeV [3]. For these results we utilized only a fraction of MoEDAL’s innovative trapping detector system. We detect the monopole by observing a persistent current induced in a superconducting magnetometer (SQUID) by the passage a monopole captured in a tracking detector element.
Figure 2. Cross-section upper limits at 95% confidence level for DY monopole production in 13 TeV pp collisions as a function of mass for spin-1/2 (left) and spin-0 (right) monopoles. The colours correspond to different monopole charges.
MoEDAL is the first experiment to place limits on the production of magnetic monopoles in 13 TeV pp collisions. Also, our search to date has probed mass ranges previously inaccessible to collider experiments for multiply charged spin-0 and spin-1/2 monopoles with a magnetic charge up to 5 times the Dirac charge (gD). Cross-section upper limits at the 95% confidence level for Drell-Yan monopole production are shown in Figure 2. A summary of the MoEDAL limits for monopole production obtained at an Ecm of 8 and 13 TeV is compared with the ATLAS limit [4], the only other LHC monopole search result, in Figure 3. The MoEDAL limits for direct production of monopole anti-monopole pairs is the best in the world for magnetic charges greater than one Dirac charge.
Figure 3 A summary of limits obtained by MoEDAL for monopole production at Ecm 8 and 13 TeV compared to the ATLAS limit.
MoEDAL has finished an initial campaign of calibration using heavy-ion beams at the NASA Space Radiation Laboratory and the CERN –SPS (NA61) as well as studies of etching conditions for the MoEDAL NTDs. The MoEDAL collaboration is now poised start to produce greatly enhanced results, with unparalleled sensitivity, using the full detector. This will enable us to search for electrically and magnetically charged highly ionizing messengers of new physics. In addition, MoEDAL is planning to expand is physics horizons by deploying a new sub-detector called MAPP (a Monopole Apparatus for detecting highly Penetrating particles). This year we expect to install a small prototype MAPP detector in a tunnel adjacent, some 40m away from IP8, in order to study physics backgrounds.
The MOEDAL experiment provides a pioneering and complementary expansion of the LHC’s discovery horizon. The "high-risk" nature of MoEDAL’s extensive physics program is justified not only by the prospect of a revolutionary breakthrough with impact far beyond the realm of particle physics but also by the unique and wide reaching constraints it can place on new physics. The unprecedented nature of the MoEDAL detector and its systematics – exemplified by its ability to retain a permanent “photographic” record of new highly-ionizing particles and even capture them for further study - will make MoEDAL an invaluable asset in the elucidation of any Terascale new physics scenario covered by its extensive physics repertoire.
Bibliography:
[1] B. Acharya et al., “The Physics Programme Of The MoEDAL Experiment At The LHC”, MoEDAL Collaboration, Int.J.Mod.Phys. A29 (2014) 1430050.
[2] B. Acharya et al., “Search for magnetic monopoles with the MoEDAL prototype trapping detector in 8 TeV proton-proton collisions at the LHC”, MoEDAL Collaboration, JHEP 1608 (2016) 067
[3] B.Acharya et al., “Search for magnetic monopoles with the MoEDAL forward trapping detector in 13 TeV proton-proton collisions at the LHC”, MoEDAL Collaboration, Phys.Rev.Lett. 118 (2017) no.6, 061801
[4] G. Aad et al., “Search for magnetic monopoles and stable particles with high electric charges in 8 TeV pp collisions with the ATLAS detector”, ATLAS Collaboration,
Phys. Rev. D93 (2016) no.5, 052009.
