Denouement: How OPERA’s Mystery Was Solved

On Friday I learned, and reported to you, that the OPERA experiment’s investigations into its early-arriving-neutrino anomaly (widely reported as `faster-than-light neutrinos’), performed with help from the nearby LVD experiment, have basically confirmed that a combination of (1) an optical fiber within the main timing system that was incorrectly screwed in, and (2) a timing drift in OPERA’s main synchronizing clock, together caused the observed 60 nanosecond early-arrival time.  The fiber provides the main effect, with the clock drift playing a subsidiary role.

However, in Friday’s post I only gave you the main idea of how this was done.  I have now finished an article that goes through the OPERA story in detail, to the extent I understand it, from the initial discovery and diagnosis of the two problems through the scientific investigation that demonstrated that the two problems probably caused all of the effect that OPERA observed.  On the one hand, the solution of the mystery is a classic scientific detective story,  instructive and interesting, and for its rather convincing and successful conclusion, the OPERA team deserves applause.  On the other hand, it leaves one wondering if this whole episode could have been avoided; why didn’t some of these investigations, which don’t seem exceptionally subtle, happen before OPERA announced its results?

Be that as it may, preliminarily (which means unofficially in this context — OPERA still has more work to do before they can announce a result officially) the revised result from OPERA-2 (the short-pulse version of OPERA) agrees with Einstein’s prediction that neutrinos at these high energies should travel at a speed unmeasurably close to the speed of light.  And thus it agrees with the ICARUS experiment’s recent result. So we now have two preliminary confirmations that the neutrinos coming to the Gran Sasso lab from CERN obey Einstein’s speed limit.