Neutrino experiment repeat at Cern finds same result

[hue]

http://www.bbc.co.uk/news/science-environment-15791236

The team behind the finding in September that neutrinos may travel faster than light has carried out an improved version of their experiment - and found the same result.

If confirmed by other experiments, the find could undermine one of the basic principles of modern physics.

Critics of the first report had said that the long bunches of neutrinos used could introduce an error into the test.

[ananda]

1. OK, doesn't appear to be an error.

Wow.

[jberryhill]

4. Or... The same undiscovered error was made twice

The neutrinos probably just found a short cut and are screwing with the physicists.

[BadgerKid]

7. That would be called systematic error.

All the more reason to have independent labs and their experiments to verify results :)

[jberryhill]

8. "All legs amputated. Frog completely deaf."

[girl gone mad]

12. The only change they made to the experiment..

was to decrease the pulse duration.

Some theoretical physicists believed that the experimentalists' methodology of only analyzing the peaks of each pulse was flawed. They thought the measurements could prove wrong because the pulses were longer than the signal.

Reducing the pulse to just 3 nanoseconds measures the speed of individual neutrinos, in essence, rather than matching up the corresponding peaks of many.

There are many more likely causes of error in this experiment, in my view. There was no consensus among physicists that a shorter pulse would produce a different result.

[caraher]

18. Right

There's a lot more to dig into, but this was an easy change and does address some possible explanations.

The best confirmation would come from a different group.

[GodlessBiker]

2. Interesting, but it may be a gravitational time dilation difference between the two clocks.

But very interesting. We'll see.

[hue]

3. re:it may be a gravitational time dilation difference between the two clocks

this would not be the case since the faster an object moves the slower the clock ticks, though nothing has been measured that travels faster than the speed of light.

[jberryhill]

5. The experiment relies on having "synchronized" clocks in two places

Which is a tough problem.

How do you know if a clock at one location is synchronized with a clock in another location?

[jayfish]

6. I believe they used a mobile atomic clock to synchronize local time sources. -NT-

[jberryhill]

13. Yes, and "mobile" and "clock" raise issues when those words appear together

There is a huge localized gravity distortion complex - otherwise known as the Alps - between the two ends of this experiment.

Let's say you have clock A, mobile clock B, and clock C.

You can put clocks A and B next to each other and get them "synchronized" to a high degree of precision.

You can then take clock B over to clock C and do the same thing.

You can even go back and forth and check clock A and Clock C against clock B multiple times if you want.

After doing all that, you have never had Clock A and Clock C in the same place. You infer that they are "synchronized" but it is a trivial consequence of relativity that you can't really know if any two separated things in the universe are in fact synchronized.

And, again, the distance between the end points of the experiment depends on clocks aboard orbiting GPS satellites, which introduces other problems.

[BadgerKid]

14. Yes, agreeing on "now" appears to be the fundamental issue.

I'd expect they would have to account for possible non-uniformity of gravitation fields, therefore time dilation effects, all along the neutrons' path. I'm doubting spherical cow assumptions won't cut it here.

[jberryhill]

15. There was a note that was published by another group

...to the effect that uncertainties caused by relativistic effects in the GPS system were of the same order of magnitude of the anomaly seen here, but... there's a reason I don't do physics anymore, lol.

You'll enjoy this:

http://dvice.com/archives/2011/10/speedy-neutrino.php

Researchers at the University of Groningen in the Netherlands went and crunched the numbers on how much relativity should have effected the experiment, and found that the correct compensation should be about 32 additional nanoseconds on each end, which neatly takes care of the 60 nanosecond speed boost that the neutrinos originally seemed to have. This all has to be peer-reviewed and confirmed, of course, but at least for now, it seems like the theory of relativity is not only safe, but confirmed once again.

[bananas]

16. It wasn't a group, it was one guy, and I think it's been discounted

Here's his revised paper: http://home.kpn.nl/vanelburg30/TOFRemarks.html
Here are some comments about it:
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=228&topic_id=84650&mesg_id=84674
http://scienceblogs.com/principles/2011/10/experimentalists_arent_idiots.php

[jberryhill]

17. Hm

Them danged little things seem to be going mighty fast.

Or the result remains unexplained.

[GodlessBiker]

9. A clock ticks more slowly in a stronger gravitational field, too. The clock...

issue is not insignificant (the two clocks may be in two different places in Earth's gravitational well) and it is something I believe they are checking out.

[jberryhill]

10. There are a lot of clocks

The distance of the course is also determined by GPS, which uses clocks on orbiting satellites.

If you are familiar with the geography between Geneva and northern Italy, there are some considerably massive objects - i.e. Alps - along the way, which also influence local gravitational conditions.

The drive from Geneva down to Chamonix and through the Mont Blanc tunnel to the Aosta valley is quite beautiful. If I were a neutrino, I wouldn't rush through it though. It's much better to take your time and take in the sights.

[hue]

11. Yes this is true! Much has to be checked out-->so far not conclusive. n/t

[caraher]

19. All this stuff about clocks and simltaneity is true and relevant...

but none of it is anything a sophomore physics major isn't already aware of. There are well-known formulas for taking into account all of these effects that have been validated in experiment after experiment, and it's extremely hard to believe the OPERA collaboration released their results in ignorance of any of it.

This is almost certainly either new physics or some kind of systematic error. Maybe there's some technical problem or an unnoticed erroneous measurement used somewhere in their analysis. I'd bet pretty strongly against any of the simplest relativity-based arguments simply.

[hue]

20. CERN Do-over Results in Faster-Than-Light Particles ... Again

http://www.technewsworld.com/story/73798.html

...Two other groups of researchers will seek to duplicate the Gran Sasso results.
They are Japan's T2K experiment and the United States' Minos experiment.

Minos "is the best candidate for this going forward" because it's claiming its measurements will be "a factor of five or so" better than what Opera's doing now, Siegel remarked.

Minos and T2K may be able to eliminate some biases that might exist in the Gran Sasso experiment...

[hunter]

21. Those damned neutrinos. Star Trek speculations would be fun...

Maybe as neutrinos oscillate they go a little faster than light and then a little slower; borrowing a little time, and then paying it back.

http://en.wikipedia.org/wiki/Neutrino_oscillation