What the study found
The study reports potential anomalies in muon-induced neutron multiplicity spectra from lead (Pb) targets. The authors say a single power-law function may not accurately model the highest-multiplicity events, and they note a small but statistically significant excess at the upper end of the spectra.
Why the authors say this matters
The authors suggest these findings may limit the accuracy of models used to describe muon-induced neutron multiplicity spectra. They also conclude that the weak depth dependence makes the anomaly unlikely to be directly linked to muon flux.
What the researchers tested
The researchers examined neutron multiplicity spectra from massive Pb targets at depths of 3, 40, 210, 583, 1166, and 4000 m.w.e. (meters of water equivalent, a measure of underground depth). The measurements were collected between 2001 and 2024 using three experimental setups with 14 or 60 He-3 neutron detectors and Pb targets weighing 306, 565, or 1134 kg, with more than six years of total acquisition time. Where available, the spectra were compared with Monte Carlo simulations.
What worked and what didn't
The data indicate that a single-power-law approach fails to account for a small excess of events at the highest multiplicities, even at shallow depths. The excess appears similar to a second power-law component, and the highest-quality data at 583 m.w.e. suggest a possible structure resembling emission of about 74, 106, 143, and 214 neutrons from the target.
What to keep in mind
The abstract describes these effects as potential anomalies and suspected structures, so the result is not presented as fully confirmed. The authors call for new underground measurements with low-cost, large-area, position-sensitive neutron arrays around multi-ton Pb targets to verify the anomalies and determine their origin.
Key points
- Potential anomalies were found in muon-induced neutron multiplicity spectra from lead targets.
- A single power-law function did not fully describe the highest-multiplicity events.
- The spectra showed a small but statistically significant excess at the upper end.
- The anomaly changed only slightly with depth and was said to be unlikely to be directly linked to muon flux.
- Data at 583 m.w.e. suggested a possible structure resembling neutron emissions of about 74, 106, 143, and 214.
Disclosure
- Research title:
- Muon-induced neutron spectra show possible high-multiplicity anomalies in lead
- Authors:
- W. H. Trzaska, A. Barzilov, T. Enqvist, K. Jędrzejczak, Marcin Kasztelan, P. Kuusiniemi, Kai Loo, Jerzy Orzechowski, M. Słupecki, J. Szabelski, T.E. Ward
- Publication date:
- 2026-03-11
- OpenAlex record:
- View
Get the weekly research newsletter
Stay current with peer-reviewed research without reading academic papers — one filtered digest, every Friday.