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CERN team claims measurement of neutrino speed >c

by turbo
Tags: anisotropy, cern, ftl, gps, new math books
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hamster143
#145
Sep23-11, 08:19 PM
P: 986
What bothers me most about this result is not so much the claim of v > c, as the magnitude of the effect. It is way, way too strong.

It is incompatible with QG-inspired Lorentz-violating dispersion relations (it's too strong, by something like 13 orders of magnitude, compared to what we'd expect.) It is incompatible with tachyons (for tachyons, speed goes up as energy goes down, and that would be hard to miss - for starters, MINOS would've seen the arrival time anomaly of ~2000 ns.) The energy scale implied by this value of (v-c)/c is in the MeV range. I could accept a slightly superluminal mass eigenstate with negative m^2 on the same order as mass differences measured in neutrino oscillations; or even a value like those produced in tritium beta decay experiments (where m^2 values down to ~-100 eV^2 have been reported). But none of these values would come even close to producing a 10^-5 effect in the speed of travel at 17 GeV.

It has to be an unaccounted-for systematic error, a large-extra-dimensions effect that increases the strength of QG-induced Lorentz violation, or something completely unexpected. I'm leaning towards a systematic error.
kmarinas86
#146
Sep23-11, 08:28 PM
P: 1,011
Quote Quote by SeventhSigma View Post
I did the math too and was able to confirm Vanadium's result of a 4 year expected difference if the neutrinos were in fact faster than light. I think I trust that supernova over this experiment. Were there any other differences in the neutrinos themselves (I tried reading the paper but it's too dense for me)?
For one, the method of acceleration is different. So if any difference is real, then the geometry and strength and dynamical motion of the magnetic field might play a role. This could lead to a different oscillation signature. It is possible that a difference in the speed may be real while us not having any immediate reasons as to why that may be. It is too early to speculate much further than on Physics Forums though. Answers to this (accounting for whether it is a statistically significant difference or not) cannot be complete or valid at this time.
turbo
#147
Sep23-11, 08:29 PM
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Quote Quote by SeventhSigma View Post
I did the math too and was able to confirm Vanadium's result of a 4 year expected difference if the neutrinos were in fact faster than light. I think I trust that supernova over this experiment. Were there any other differences in the neutrinos themselves (I tried reading the paper but it's too dense for me)?
Put yourself in the position of an observational astronomer, and then extrapolate to the position of a theorist in stellar evolution. Do we know that photons and neutrinos are emitted at the same time in a SN? Do we know that if there is a differential in the emission of copious amounts of photons and neutrinos that it can be constrained to minutes, hours, months, years? Are any of these time-frames relevant if we don't know what happens when a star self-destructs?

We have a lot of stars to look at and supernovas of all types get lots of attention. Still, we don't know all that we need to about the birth, life, and death of stars. We have some compelling models, but our lives are very short and the lives of stars are very long, so there is a sampling problem...
ghwellsjr
#148
Sep23-11, 08:39 PM
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Quote Quote by PAllen View Post
Quote Quote by ghwellsjr View Post
I don't see how clocks adjusted by GPS can get around the concern that I have. Consider the atomic clocks at Greenwich and Boulder running at different elevations and therefore running at different rates. If we measured the round-trip speed of light at both locations using their own atomic clocks, we'd get the correct answer of c. But if we used a common time generated by GPS, we will no longer get the correct answer of c at both locations, correct?
Yes, that's true, but not relevant to what they are doing.
Is it not relevant because the errors caused by the different time rates are too small to matter in this experiment or because the experimenters took the different rates into account?
peefer
#149
Sep24-11, 12:12 AM
P: 4
'Just standing back, ignoring the particle physics, looking a this from a nuts and bolts perspective ...

60ns. 18m. This seems too crazy-big to be a systematic error, right? What about this:

GPS-based distance measurements are made at the earth's surface. Then, most significantly at the OPERA detector, adjustments are made for the detector's position relative to the GPS receiver. So, if the neutrino detector is 1400m underground, and 50m toward CERN, the correction is about -50m. Right? Wrong.

Since the earth isn't flat like it used to be (sorry, I can't cite a reference for this offhand), two deep holes some distance apart are not parallel. They converge toward the earth's center. The bottom of the 1400m deep hole at OPERA is in fact 26m closer to CERN than the top of the hole where the GPS receiver is, if you work out the numbers. (The extreme case would be a 1400m hole in New Delhi, India, which is about 1400m closer to New York. With OPERA and LHC only 730km apart, the effect is much smaller, but relevant.)

26 metres. That would quite nicely explain the 60ns premature neutrino detection within statistical error.

Of course, the scientists already must have considered this, right? It sure would be embarrassing if they didn't.
hamster143
#150
Sep24-11, 12:20 AM
P: 986
Quote Quote by peefer View Post
'Just standing back, ignoring the particle physics, looking a this from a nuts and bolts perspective ...

60ns. 18m. This seems too crazy-big to be a systematic error, right? What about this:

GPS-based distance measurements are made at the earth's surface. Then, most significantly at the OPERA detector, adjustments are made for the detector's position relative to the GPS receiver. So, if the neutrino detector is 1400m underground, and 50m toward CERN, the correction is about -50m.
This is logical, but wrong. :) OPERA is not exactly "underground" (as in, "in an abandoned mine".) It sits just off a 10-km highway tunnel through the mountain. They took two GPS units and measured locations of both ends of the tunnel, and then tracked back from the entrances to the facility to determine its exact coordinates.
Lord Crc
#151
Sep24-11, 12:21 AM
P: 88
Quote Quote by peefer View Post
Of course, the scientists already must have considered this, right? It sure would be embarrassing if they didn't.
Highly likely. They have GPS receivers at both ends of the tunnel, and they triangulated from both ends. They said the two measurements agree very closely. It seems improbable that they would get close agreement between the two if they had ignored this.
f95toli
#152
Sep24-11, 05:26 AM
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Quote Quote by Nikpav View Post
Significant part of that measurement relies on use of GPS timing distribution.

I propose to perform an experiment to verify that it is correct.
It is based on the fact that current stability performance of atomic clocks is at the level of 10^-14,
or about 10nS error per day (24 hours).
I propose to use some portable atomic clock device to first synchronize at one site (e.g. OPERA)
and then physically move ( by cars and airplaine) to another one within few hours.
During that period of time it should not drift for more then a few nSec.
Such precision should be adequate to calibrate against possible GPS related errors.

Thank you for your attention
This experiment has been done many,many times. Note that the UTC is based on comparing lots of clocks around the world, meaning there are well developed methods for time transfer. Time transfer does become tricky with very accurate clocks due to GR effects that can not be compensated for(due to uncertainties in position); but this is only an issue for the best optical clocks which are orders of magnitude better than the cesium clocks useful for the UTC (10^-17 level or so).
Again. this is NOT a problem with GPS time keeping, 60 ns is a very long time inmodern time metrology .
harrylin
#153
Sep24-11, 05:37 AM
P: 3,181
Quote Quote by keji8341 View Post
Neutrino results challenge cornerstone of modern physics --- Sagnac effect?

Within 60 ns, light goes through 18 m.

The Earth ‘s velocity around the Sun is 30 km.
The time during which light goes through 730 km is: 730km/300,000 km = 0.00243 s.
Within 0.00243 s, the Earth around the Sun goes through 30 km/s x 0.00243 s = 73 m.
With the location effect of the experiment taken into account, 18 m and 73 m are in the same order.
Not that one: GPS is ECI frame based. The Sagnac effect that the experimenters appear to have overlooked is the rotation speed of the Earth. However, as we discussed before, that effect is still more than an order of magnitude too small to explain this riddle (between 0 and 465* m/s instead of 7500 m/s).

*v of equator: 40000 km / (24x60x60) s
divvydan
#154
Sep24-11, 05:40 AM
P: 1
Hi everyone, interested newbie.

Was sent a link today to a page that explains why the result was wrong statistically (http://johncostella.webs.com/neutrino-blunder.pdf).

Leaving aside any concern on the background of the person involved, I was left unconvinced by the argument put forward but I don't know enough to be able be definitive about it.

Could one of the more knowledgeable people (particularly in statistics) have a quick read and post their thoughts?
Vanadium 50
#155
Sep24-11, 06:10 AM
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According to the Costella paper, if I want to measure the distance between the left end of a piece of wood and a point to its left, it depends on how long the piece of wood extends to the right. That's nonsense.
TrickyDicky
#156
Sep24-11, 06:54 AM
P: 3,004
Quote Quote by Harisankar View Post
This might sound stupid,but I can't get it out of my mind,so i' asking it.
They have VERIFIED that it's neutrinos didn't they? Or they just assumed it's neutrinos because that is what is expected?
Quote Quote by hamster143 View Post
The accelerator is expected to produce neutrinos. The detector is expected to detect neutrinos. Timing of collisions seen by the detector matches exactly the timing of protons emitted by the accelerator. Nothing except neutrinos is known to be capable of penetrating through 700 km of rock. Processes inside the accelerator are well understood and it would be extremely surprising to find any unknown particles produced in bulk.
The fact is that if we leave aside the systematic error as the most likely cause of this, this is the point where the search must be and surely will be centered by serious theorists long time before they even seriously consider something's wrong with relativity. (the media is a different matter, all newpapers I've seen have already decided "Einstein was wrong").
As hamster 143 correctly answered the "FTL neutrinos" are assumed to be neutrinos because they are expected to be the neutrinos coming from the accelerator (measuring the time distributions of protons for each extraction for which neutrino interactions are observed in the detector) based on measured neutrino interaction time distributions. These statistical results can't completely rule out for instance that the "arriving" neutrinos' signal is due to some local neutrino-like interaction totally unrelated to the proton accelerator.
kfmfe04
#157
Sep24-11, 07:24 AM
P: 36
in one of the videos about OPERA, I saw a mention of fiber carrying light along the path - assuming that this light is subject to the same mass distributions as you ghc mentioned, couldn't you work backward with this fiber as the calibration point for c, and determine if the neutrinos have traveled faster than the photons in this fiber?
Vanadium 50
#158
Sep24-11, 07:58 AM
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Quote Quote by TrickyDicky View Post
These statistical results can't completely rule out for instance that the "arriving" neutrinos' signal is due to some local neutrino-like interaction totally unrelated to the proton accelerator.
When the accelerator is on, they see neutrinos. When it's off, they don't. That's pretty convincing.
DevilsAvocado
#159
Sep24-11, 10:37 AM
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Quote Quote by f95toli View Post
Again. this is NOT a problem with GPS time keeping, 60 ns is a very long time inmodern time metrology .
Could you please help me out here (because I’m about to lose my mind [almost])...

IF something is moving faster than light then the Lorentz factor γ (using c as a constant) must be somewhat 'adjusted', right? The Lorentz factor appears in several equations in Special Relativity, including time dilation, right? Time dilation is used in the GPS system to adjust the clocks involved for relativistic effects, right?


Lorentz factor as a function of velocity

So, how can we trust the GPS timing if we at the same time are looking for data that will 'overthrow' the scientific foundation the system is built on?? I don’t get it...


Please note: I know that I’m wrong (to many extremely smart people around to miss this), I just can’t see it myself...
TrickyDicky
#160
Sep24-11, 10:58 AM
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Quote Quote by Vanadium 50 View Post
When the accelerator is on, they see neutrinos. When it's off, they don't. That's pretty convincing.
It is not as simple as that and anyone who has bothered to look up the paper or knows about neutrino detection knows it, so you ought to know.
If experimental error is not found,the very detection of neutrinos 60ns before they should if they were coming from the accelerator should make you consider this possibility, unless you are one of those speculating about the fall of modern physics as we know it.
Vanadium 50
#161
Sep24-11, 11:54 AM
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Quote Quote by TrickyDicky View Post
It is not as simple as that and anyone who has bothered to look up the paper or knows about neutrino detection knows it,
That's exactly how it's done. You have the neutrino beam produced for a fraction of a second every SPS cycle, and the detector sees more events - substantially more - in this period than at other times. Furthermore, this tracks the accelerator operation at all time periods. Machine off for a week? No neutrinos that week.

You can see it graphically in the paper; figure 11.
keji8341
#162
Sep24-11, 12:23 PM
P: 94
Quote Quote by Buckleymanor View Post
Surely the one way neutrino method of measuring there speed could be adapted to measure the single-way speed of photons.
If it can work for neutrinos why can't it work for photons.
And if by any chance it ain't possible, though doubtfull, you could allways send the neutrinos back the other way and measure there velocity in the opposite direction.
It is more convincing that experiments for both neutrino and photon are done based on the same clock synchronization. The key point is the clock synchronization.


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