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 … Read more

The Mathematician You Haven’t Heard Of (But Physicists Have)

It is quite amusing to find that just as I am drafting an article on mass and energy, in which Emmy Noether, one of the important mathematicians and mathematical physicists of the last century, makes a central appearance, the New York Times decides this is the day to make her deservedly famous among the wider … Read more

This Time, ICARUS Really DOES Refute OPERA

Well, ICARUS flies even higher, and so far shows no sign of losing its wings.

Remember OPERA, the experiment that claimed neutrinos sent from the CERN lab in Switzerland to the Gran Sasso lab in Italy arrive earlier than they were expected to? And that a couple of weeks ago had to admit they’d found a couple of problems that were large enough to scrap their result for the moment, and that require additional investigation?

And remember ICARUS, OPERA’s neighbor in the same Gran Sasso lab in Italy, which measured the energies of neutrinos from the CERN neutrino beam, and showed they were not altered in flight? And thus proved that if the neutrinos really were traveling faster than light, they did not exhibit anything like the variant of Cerenkov radiation that was suggested by and calculated by Cohen and Glashow?

Now, ICARUS’s result from the fall didn’t directly refute the OPERA experiment (despite some claims, even by them) but it certainly added to the aura of extreme implausibility that surrounded the whole story.

Well, this time ICARUS refutes OPERA. Essentially, they did the same measurement as OPERA-2, as I called the short-pulse variant of OPERA’s original experiment.  They took data at the same time as OPERA-2, in the same neutrino beam, in the same laboratory.  It took them a while to do all the distance and timing calibrations that OPERA had done many months ago, but they’re finished now. And whereas OPERA-2 gets the same result as OPERA-1— an early arrival of 60 nanoseconds (billionths of a second) — ICARUS finds a result consistent with an on-time arrival. Same measurement, different answer. At least one experiment made a mistake; and one result is vastly more plausible than the other, so I think the consensus is pretty clear in the matter.

ICARUS's 7 neutrinos (dark blue histogram), measured in October and November, arrived as expected to within 10 nanoseconds (billionths of a second). OPERA's result (but not its neutrinos) is shown at right, at approximately 58 nanoseconds early arrival.

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Everybody’s a Critic

I wanted to make a few assorted comments about the OPERA experiment’s painful climb-down, and about yesterday’s widespread response to it, which bothered me a lot.  You may want to read my initial post from yesterday, and also my attempt to sharpen the main question OPERA left unanswered in my second post.  [ALSO: look ahead to the next post, in which many of the confusions that were still present at the time of this post were resolved.]

Over the past day I’ve learned enough to be pretty convinced (but not certain) that the situation that we are in is case (e) [or a version of case (d)] as described in yesterday’s post: that probably the previous OPERA experimental data is tainted and we can draw no conclusions from it at all.  It’s not that they found a problem that shifts their data so that it is consistent with Einstein’s relativity [case (b) from yesterday], and they can say that the neutrinos travel as expected.  (Press reports that said so are just wrong.) It’s that they found a problem that means their data from last year can’t be interpreted at all… at least, not at the moment, and maybe not ever.  If true, this would indeed mean that there is no longer any data from OPERA that can be used to measure neutrino speeds to good accuracy, and we’re back where we were before OPERA ran in the first place: with no reason to think there’s anything amiss with Einstein’s relativity equations.  As for OPERA, the only way forward is to rerun the experiment (apparently in March-April-May.)

[The NY Times article that appeared today (which attributes OPERA, a non-CERN experiment, to CERN; what has journalism come to these days?) has some additional details, but if you read it carefully, those details don’t change anything written in this post.  See the first comment at the very end of this post.]

Ok, some comments.

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Space Travel is Relatively Complicated

The principle of relativity comes up regularly in the context of space travel, and this week’s launch of NASA’s “Curiosity” rover mission was no exception.  The BBC has a pretty nice article about it, but as happens so often in press articles, it stumbles in a big way at one point.  Quoting from the article: … Read more

Climate Change in Climate Change

The most important thing that happened this week in Berkeley, California was definitely not the news of a  small and probably ephemeral excess of multi-lepton events at the Large Hadron Collider‘s CMS experiment — and probably not even the disconcerting earthquakes on (near?) the strained Hayward fault — it was the (public but not yet … Read more

Don’t Cancel the Webb Telescope!

Terrible news indeed, that there is a serious chance that the James Webb Telescope, the successor to the Hubble space telescope, will be cancelled by the House of Representatives.   I myself am horrified watching this country voluntarily give up its leadership in one scientific field after another, killing projects that are not even a … Read more

Space Shuttle

30 years ago, I took a battery-operated radio along on an 8th grade camping trip so I could listen with excitement to the first space shuttle launch.  Today I watched the last one on streaming video, sadness mixed in with the thrill.   And once, 12 years ago, I witnessed a nighttime space shuttle launch in … Read more