Last night a preprint appeared on the arXiv, with a re-analysis of old 1992-5 LEP data, looking at the dimuon spectrum for b-tagged (identified as involving a b-quark) events. An excess around 30 GeV was found, which would indicate a possible new particle around that energy. The author quotes various significance numbers for the bump, with look-elsewhere effect included, of 2.4 to 2.9 sigma.
Thinking a bit about the look-elsewhere effect here, something very funny is going on. To properly compute the look-elsewhere effect, one really should know how many other channels the author looked at and found nothing, but there’s no mention of looking at other channels. Why did this particular physicist decide to go and reanalyze LEP data, looking only at the b-tagged dimuon spectrum (and it seems he’s doing this by himself)? It’s hard to understand why anyone would do this, unless perhaps they had heard that one of the LHC experiments might be seeing something in the b-tagged dimuon spectrum, say, around 30 GeV.
We’ll likely find out more about this story soon. If the LHC experiments haven’t been looking closely at this particular channel, they will do so now. 30 GeV is low enough that I don’t see why you would need the Run 2 13 TeV data, this should be in the older Run 1 data.
I should make the obvious remark though: this is an extraordinary claim, and the evidence for a new particle is very far from the extraordinary level. So, at a high confidence level, the probability is that there’s nothing there.
Update: Tommaso has an update with more about this: the author was not a member of ALEPH and that collboration does not support this but thinks this is bogus. It appears that the signal is spurious, with the muons coming from semileptonic b decays, not a new particle. Still a mystery: why was this physicist looking at this old data for one very specific signal?
Update: The talk today by Nate Odell of CMS at the LPC Physics Forum at Fermilab is not public, but the title is: “Dimuon 29 GeV analysis”. Any guess whether that has something to do with this story about 30 GeV dimuons?
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