From what I could gather, the issue is with a cable connecting two modules of the electromagnetic calorimeter. It was discovered that this particular cable had a short-circuit, as a result of which it was repeatedly sending pulses with similar characteristics as those expected from a 125 GeV Higgs boson decaying to a pair of photons. Recall that the tantalizing hints of the Higgs boson reported last year by the ATLAS and CMS collaborations were almost entirely based on the observations of a bump in the diphoton mass spectrum, see the graph on the right. It now appears that at least a part of that bump can be blamed on the loose cable. Meanwhile, the CMS collaboration also reported a problem yesterday. From what I could understand, in this case it is not a hardware problem but a software bug originating due to the American and European parts of CMS using different units of mass (kilograms vs pounds). It is not yet clear if this issue affects the Higgs searches, but it is not unlikely that, when the data analysis is corrected, the bump in the diphoton spectrum will shift to a different location or completely disappear.
In the end, it is probable that the Higgs searches at the LHC will have to be redone from scratch during the 2012 run. In that case the LHC may lose its place in the queue, and the glory may go to the Tevatron who recently reported a signal of the Higgs boson decaying to a pair of bottom quarks.
An official statement from CERN is expected on Monday morning. Stay tuned as the story unfolds.
Update: Obviously, this story is an April Fools joke. If you forgot what date it was, you could easily realize this was not a true story because of the following inaccuracies:
- OPERA is not a CERN experiment, CERN only provides the neutrino beam for that collaboration (although, because of some awkward politics, CERN assumed in the eyes of the world a certain moral responsibility for OPERA).
- There's no way a loose cable can fake the Higgs signal; thousands things can but not this one.
- On both sides of the Atlantic the elementary particle masses are measured in GeV.
- The ATLAS and CMS detectors thousands cables, so if one of them went loose we probably would never know ;-)