ATTN LMNO: PLEASE TO EXPLAIN

[Jasper]

The follow-up is: physicists are confused, and not sure what to make of it all.

...And that's news, is it?

[Cain]

The follow-up is: physicists are confused, and not sure what to make of it all.

...And that's news, is it?

IT IS NOW!

[Golden Applesauce]

Can't we do an "absolute zero" type extrapolation for this, like what is done for Kelvins? Since we've never measured anything at absolute zero temperature either.

IF the explanation is that photons have a real (albeit tiny) mass and therefore only travel at a near-unity fraction of c, then we'd need to figure out what their mass is first before any extrapolation takes place.  Given that everyone is (was?) pretty sure that photons have no mass and that they've been pretty thoroughly studied, I suspect we don't have the instruments or the techniques to measure a photon's mass precisely enough in the first place.

My money's on photons have no rest mass, and the fact that neutrinos have nonzero mass does something something to spacetime that lets them travel through space relative to them at near c, but that appears to observers as above c?  Like they make a chain of tiny wormholes or something?  That's IF the results turn out to hold.

[Rumckle]

This blog is usually pretty accurate with it's particle physics:

http://resonaances.blogspot.com/2011/09/phantom-of-opera.html

[Triple Zero]

This blog is usually pretty accurate with it's particle physics:

http://resonaances.blogspot.com/2011/09/phantom-of-opera.html

"As everyone knows by now, the OPERA collaboration announced that muon neutrinos produced at CERN arrive to a detector 700 kilometers away in Gran Sasso about 60 nanoseconds earlier than expected if they traveled at the speed of light (incidentally, trains traveling the same route arrive always late)."

[Kai]

This blog is usually pretty accurate with it's particle physics:

http://resonaances.blogspot.com/2011/09/phantom-of-opera.html

We should weigh this evidence against the analysis of OPERA which does not appear rock solid. Recall that OPERA was conceived to observe tau neutrino appearance, not to measure the neutrino speed, and indeed there are certain aspects of the experimental set-up that call for caution. The most worrying is the fact that OPERA has no way to know the precise production time of a neutrino it detects, as it could be produced anytime during a 10 microsecond long proton pulse that creates the neutrinos at CERN. To go around this problem they need a statistical approach. Namely, they measure the time delay of the neutrino arrival in Gran Sasso with respect to the start of the proton pulse at CERN. Then they fit the time distribution to the templates based on the measured shape of the proton pulse, assuming various hypotheses about the neutrino travel time. In this manner they find that the best fit is for the travel time is 60 nanoseconds smaller than what one would expect if the neutrinos traveled at the speed of light. However, one could easily imagine that the systematic errors of this procedure have been underestimated, for example, the shape of the rise and the fall-off of the proton pulse have been inaccurately measured. OPERA does a very good job arguing that the distance from CERN to Gran Sasso can be determined to 20 cm precision, or that synchronizing the clocks in these two labs is possible to 1 nanosecond precision, but the systematic uncertainties on the shape of the proton pulse are not carefully addressed (and, during the seminar at CERN, the questions concerning this issue were the ones that confounded the speaker the most).

IOW, when your range of error is large, your precision is weak, especially when you can't actually account for the error properly. I expect that the replication will show this.

But I am glad I didn't jump jump to the "you're wrong" conclusion immediately.

[Don Coyote]

From some guy who uses his mighty skills to theorycraft for WoW

This really feels like a total non-story to me, but I'm a little biased since I have a thesis to defend on the topic next week. The neutrinos saw a fractional advancement of ~60 nanoseconds in a total traversal time of 2.4 milliseconds. Without more information, it's impossible to tell whether 60 ns is relevant.

For example, I have an experiment running right now where photons are "traveling" faster than the speed of light. That doesn't mean that Einstein causality is wrong, or that the cornerstones of physics are crumbling beneath our feet. It means that someone out there doesn't understand what those cornerstones actually say, and what their implications are.

There's nothing special about making a particle appear to travel faster than the speed of light. It happens all the time. The speed of light is only the cosmic speed limit for signal transit, so unless you can prove that those neutrinos carry information, it's meaningless. I'd like to know the temporal width of their neutrinos, simply because that would help determine if what they're seeing is interesting. If they're seeing 60 ns of advancement on a 100+ nanosecond particle, then the results aren't ground-breaking, even if they are surprising (is rock really that dispersive?).

The confusing part, to me, is why the very first thing they thought of wasn't dispersive propagation effects. Maybe particle physicists don't see that very often?

[Kai]

That quote honestly doesn't make any sense at all.

[LMNO]

Ok, I have a new physics guy -- as it turns out, he's been working on a nutrino project in Japan for a few years (this guy, if you want to check my references).

Anyway, this is his take on it:

Most likely, there is an error somewhere.  Measuring the time between the birth of neutrinos and its arrival at a detector 730 km away accurately is not a trivial task. They say that they accuracy is 10 ns, which is very hard to achieve. 10 ns corresponds to 2 m of electric cable.

In regards to the idea that particles that were created already moving at the speed of light, the neutrinos are created from decaying pions that are created from protons hitting a target. To produce neutrino already moving faster than c you will need protons with literally infinite energy.

He also provided this link: http://news.sciencemag.org/sciencenow/2011/09/neutrinos-travel-faster-than-lig.html which says:

The big question is whether OPERA researchers have discovered particles going faster than light, or whether they have been misled by an unidentified "systematic error" in their experiment that's making the time look artificially short. Chang Kee Jung, a neutrino physicist at Stony Brook University in New York, says he'd wager that the result is the product of a systematic error. "I wouldn't bet my wife and kids because they'd get mad," he says. "But I'd bet my house."

Jung, who is U.S. spokesperson for a similar experiment in Japan called T2K, says the tricky part is accurately measuring the time between when the neutrinos are born by slamming a burst of protons into a solid target and when they actually reach the detector. That timing relies on the global positioning system, and the GPS measurements can have uncertainties of tens of nanoseconds. "I would be very interested in how they got a 10-nanosecond uncertainty, because from the systematics of GPS and the electronics, I think that's a very hard number to get."

And finally:

[Kai]

Thanks, LMNO. Error bars are not to be ignored.

Also, the GPS XKCD reference is cool for me, because the time dilation offset in global positioning experiments is a direct result of the Hafele-Keating Experiment which showed time dilation in jets going different directions around the planet. And Joe Hafele is my grandfather.