Has LZ seen a WIMP?
One of the candidates for the dark matter that seems to pervade the cosmos is a Weakly Interacting Massive Particle (WIMP, for short). Such particles are hypothetical but, if they exist they could have been produced in large numbers in the early Universe. Among the possible WIMPs are supersymmetric particles, but there are alternative candidates. Whatever their nature it is possible that they could be directed directly in collisions with regular matter but, because they are weakly interacting, the cross-section for such events is low and potentially masked by background events caused by radioactive decays. So far these experiments have drawn a collective blank (and a number of false alarms).
One experiment trying to detect dark matter directly is LUX-ZEPLIN (LZ for short) which is based at the Sanford Underground Research Facility in South Dakota in the USA but is a collaboration of 30 institutions worldwide, including the the UK, Portugal and South Korea as well as the USA. This experiment tries to detect WIMPs using an ultra-sensitive detector made of 7 tonnes of liquid xenon to hunt for signals of their interactions with atomic nuclei.
Today there was a potentially exciting announcement that LZ may have seen a WIMP, in a preprint with the following abstract:
There is also a scientific presentation by Sam Eriksen from which I have extracted the crucial figure(s):
The event causing the excitement was detected over three years ago, on 16th June 2023. You can see it as the little black dot towards the upper right of the dashed square in the left hand panel. The LZ signal does appear unlikely to have been generated by known background events, but that does not necessarily mean that it is likely to be WIMP. The statistical significance quoted is not sufficiently high for it to be regarded as a clear detection; the implied odds are roughly the same as the odds that you, the reader, have a birthday on 16th June…
In the Dark 
September 1, 2026 at 11:15 pm
Why 38 months to be made public?
September 2, 2026 at 9:54 am
Were I a cynical person I might suggest that they have a grant review coming up and decided to put this out just in advance of it.
September 2, 2026 at 3:01 am
@telescoper.blog Not really serious, see this post https://tritonstation.com/2026/09/01/you-have-one-1-dark-matter-particle-detection/
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September 2, 2026 at 3:01 am
@telescoper.blog Not really serious, see this post https://tritonstation.com/2026/09/01/you-have-one-1-dark-matter-particle-detection/
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September 2, 2026 at 10:28 am
@telescoper.blog I can see excess events from I125. Now I know where the missing Brachytherapy seeds went.
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September 2, 2026 at 3:18 pm
It will take more than one. We need a bunch of WIMPs to verify this.
September 2, 2026 at 3:31 pm
Certainly. It may well be an artefact of an unanticipated background. It will take time to understand the background better and find more similar events.