Vol. 1, No. 47 The Journal of Record for Magnetic Monopole Research Saturday, May 3, 2026

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UPDATE — IceCube reports 3.2σ excess in upgoing track sample, consistent with intermediate-mass monopole flux. FILED — MoEDAL-MAPP collaboration submits Run 3 NTD analysis to JHEP. NOTE — SuperKEKB Belle II calibration extended to mid-Q3; cosmic-ray monopole search delayed. BRIEF — ANTARES legacy reanalysis tightens Parker bound by factor of 1.4. ALERT — LIGO O5 commissioning team flags candidate transient compatible with monopole-catalysed proton decay.
Breaking · Experiment By Dr. Helena Marquez, Senior Correspondent Filed 06:14 GMT

MoEDAL Reports First Candidate Track Consistent with a Light Magnetic Monopole at the LHC

After eleven years of nuclear-track-detector exposure beneath the LHCb cavern, the MoEDAL collaboration says a single candidate signature has survived all known background cuts. Physicists urge caution; theorists urge champagne.

The announcement, released at 04:00 Geneva time and confirmed in a tightly choreographed seminar in the Main Auditorium at CERN, marks the first time in the LHC era that a permanent-magnet detector has produced a candidate event that the collaboration is unwilling to dismiss outright. The signature — a near-vertical, heavily ionizing track recorded across nine stacked CR-39 plates — carries an etch-pit profile that, the spokesperson said, “does not currently admit a conventional explanation.”

The candidate, designated MoEDAL-2026-K7, falls within the kinematic window for a Dirac monopole of mass 950–1450 GeV/c2. The collaboration stresses that a single event, drawn from a search with non-trivial trial factors across exposure campaigns, is not a discovery. Independent re-scanning by the Alberta and Bologna groups is already underway.

Reaction within the theoretical community has been swift and characteristically divided. “If this survives, it is the most significant event in particle physics since 2012,” said Prof. Aiko Tanabe (IAS Princeton). Others, including the Cambridge cosmology group, point to the difficulty of reconciling such a mass with inflationary dilution arguments.

A second exposure campaign, MoEDAL-MAPP II, is scheduled to take data through the remainder of Run 3 and into the High-Luminosity era. The collaboration will not comment on the candidate's significance until plate-replication analysis concludes in late August.

Filed under: Experimental Particle Physics · LHC · MoEDAL 8 min read
Theory · Long Read

Reconsidering the Polyakov–'t Hooft Construction in Light of Recent Lattice Results

By Prof. Renaud Dussault · Theoretical Physics Editor

A new lattice study from the Tsukuba–Edinburgh consortium suggests the topological structure underlying classical monopole solutions may be more sensitive to gauge-coupling discretization than commonly assumed. The implications, our correspondent argues, are larger than the abstract suggests.

The 1974 construction of 't Hooft and Polyakov — in which a magnetic monopole emerges as a topological soliton of a spontaneously broken non-Abelian gauge theory — has, for half a century, been treated as the textbook anchor of monopole physics. The recent arXiv:2604.11982 preprint from the Tsukuba group does not overturn that picture, but it does sharpen a question that has been quietly accumulating force in the literature: how robust is the soliton when the underlying gauge theory is regulated on a finite lattice?

The Tsukuba team's principal claim is straightforward. Using a domain-wall fermion regulator and a continuum-limit extrapolation across four lattice spacings, they find that the static monopole self-energy converges to a value approximately 14 per cent below the semi-classical prediction. The difference is well outside their quoted uncertainty.

What makes the result interesting, rather than merely technical, is the trajectory it traces. The semi-classical mass formula has long been known to receive radiative corrections; what is new is the suggestion that, in the deep infrared, the structure of the configuration itself — the radial profile, the core size, the magnetic charge distribution — deviates measurably from the original ansatz.

The implications cut in two directions. For phenomenology, a lighter monopole is, all else equal, an easier monopole to find — the kinematic windows of MoEDAL, IceCube, and ANTARES all shift. For cosmology, a lighter relic is, conversely, a harder relic to dilute: the Kibble–Zurek estimates of post-inflation abundance must be reconsidered.

Editor's note: a longer companion analysis appears in this week's Theory section.

Continued in the Theory supplement ›

Experimental Briefs

Short reports filed this week from the principal monopole-search collaborations.

MoEDAL

Plate-replication analysis of candidate K7 begins at Bologna

Independent etching of the duplicate CR-39 stack is expected to yield results by August. A null result at Bologna would not, in itself, be sufficient to retract the candidate.

CERN, Geneva · April 30
IceCube

Upgoing-track excess re-examined with full Run 7 livetime

The 3.2σ deviation reported in March persists with the addition of three months of further exposure. The collaboration declines to characterize the result as a hint.

South Pole · April 28
SLIM

Bolivian high-altitude exposure yields no candidates above 10−16 cm−2·sr−1·s−1

The third Chacaltaya campaign closes with the strongest published flux limit on intermediate-mass cosmic monopoles.

La Paz · April 25
ANTARES

Legacy reanalysis improves Parker-bound saturation by 40 per cent

A reprocessing of the 2008–2022 dataset using the updated KM3 reconstruction pipeline produces tighter exclusion contours.

Toulon · April 22
SQUID-S

Stanford induction loop reports first 30-day continuous run

No persistent flux jumps consistent with monopole transit are observed; the noise floor reaches 0.05 Φ0/Hz1/2.

Palo Alto · April 19
Belle II

Cosmic-ray monopole search delayed pending calibration

An unrelated tracker calibration issue at SuperKEKB postpones the planned analysis to the third quarter.

Tsukuba · April 16
Opinion

A Single Event Is Not a Discovery. It Is, However, a Reason to Pay Attention.

An editorial · The Editors

The instinct, on encountering a single anomalous event in a half-century-long search, is either to dismiss it — the Look-Elsewhere effect; the trials factor; the persistent human tendency to over-read noise — or to embrace it. We are sceptical of both responses.

What MoEDAL has produced is not a discovery. The collaboration says so plainly. But what it has produced is a candidate that has survived a decade of exposure, three independent etching protocols, and the kind of background-rejection programme that, in the LHC era, has become more conservative, not less. That is worth saying, and it is worth saying calmly.

The next eighteen months will resolve the question. Until then, we suggest the appropriate response is the one the collaboration itself has modelled: neither retraction nor celebration, but careful, public work.

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