On hadron colliders, dark matter and black holes

[torstan]

@Redrobes - my guess is synchronised atomic clocks at both locations so they can compare readings at both places.

The likely next step is for Fermilab to reproduce the experiment and see if they can replicate the results.

And the 60ns is +/- 10ns so that gives you an idea of the difficulty there. The size of the error is not in the measuring apparatus, but I'm guessing it comes from the fact that you're measuring a bunch of neutrinos rather than a single one. It's hard to find neutrinos so you need a bunch. It's also hard to make just one, so you get a set of them. Now a bunch has a size and you're never going to pick just one out of there. So the length of the bunch will relate to the error on the arrival time measurement.

@cantab Yep there's nothing wrong with things going faster than the speed of light. Tachyons are totally legit. But we can't make them and send messages with them - or certainly not until now. The hard and fast law is that you can't go from over the speed of light to under the speed of light. You're on one side or the other. Now neutrinos are massive particles but are so light they go close to the speed of light. Measuring exactly how fast is tricky. The supernova measurement was a good check that they actually travel at almost exactly the speed of light. But yes, tachyons would be a good first go-to as it leaves relativity intact.

[torstan]

And the paper's up: http://arxiv.org/abs/1109.4897

Love the free access physics arxiv. The conclusion's worth a read:

Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results.

[ravells]

Can I commission you to build a warp drive for me please Torstan? It'll be much more fun than making maps!

[Steel General]

Love the free access physics arxiv. The conclusion's worth a read:

I think I hurt my brain trying to read that...

[Jaxilon]

I'm not a Physicist nor do I play one on TV. I'm just happy if I can grasp the concepts.

I have not read the paper linked above because I was afraid I wouldn't know what I was reading. I then hit this news article on the BBC website and now that I think I have a clue what is being talked about I want to read the paper Torstan linked as soon as I get a chance. I don't know if the news article is dumbed down but I figure it might help ease someone else into this if they are tentative about trying to read a paper written for the Physics experts.

[cantab]

I wonder, could the problem be in calculating the time taken by light to arrive? Specifically, how much variation could the mass of the Alps, and the distribution within it, cause?

[bartmoss]

There was a 2h news conference on the subject that ended an hour ago, did anybody watch it? I only caught a few minutes as I was still at work.

And the paper's up: http://arxiv.org/abs/1109.4897

Love the free access physics arxiv. The conclusion's worth a read:

That didn't stop any of the news sites...

[torstan]

@cantab - nope, the speed of light that comes into the equation here is the absolute speed of light in a vacuum - not one modified by passage through matter. That being said, if there were a non-trivial effect in the synchronisation of the GPS time synhronisation that could do it. But they've done all the obvious checks - and a whole host of non-trivial checks - to make sure that's not the case.

The other thing that could cause it is that they might have got the distance wrong. They're calculating the speed of the neutrinos using:

speed=distance/time

So at the basic level you need to make sure you've not screwed up the time calculation, or the distance measurement. Now this is a hard problem. You need to make sure you have two clocks at the start and finish that tiem the emission and arrival of neutrinos to within nano-seconds. For context - we couldn't even detect neutrinos untel then end of the last century, let alone time their transit times. Also, gravity affects the speed that clocks tick, so you need to make damn sure your clocks and your GPS satellite all take that into account properly.

Now for the distance - you need to know the distance from CERN to Gran Sasso to within 20cm. That's a pretty small error on a 730km distance measurement, especially when one end of it is under a mountain. Things that have to be accounted for are continental drift, earthquakes and the tidal forces of the moon on the earth's crust. They claim they've got all that under control - which is a mind blowing feat in and of itself.

With all that taken into account they've got the neutrinos getting from A to B faster than it would be possible to send light across the same distance in a vacuum.

[RPMiller]

What if, and this is a really out there idea, a micro black hole was actually created along the path that the neutrinos were passing and they were unable to detect it for some reason. Would it be possible for the black hole to suck in the neutrinos and spit them out a given distance away, but in a shorter time span? Essentially, a miniature wormhole being created. Like I said, probably total science fiction, but hey, you never know.

[cantab]

@cantab - nope, the speed of light that comes into the equation here is the absolute speed of light in a vacuum - not one modified by passage through matter.

It's not passage through matter I'm on about, but passage through the gravitational field of that matter - and the fact we don't know that gravitational field precisely (since we don't know exactly what density of rocks are where underground). I don't know enough GR to actually calculate the difference it could make.

RPMiller: The measurements have been aggregated over two or three years. A micro black hole isn't sticking around for that long.