Merged Puzzling results from CERN

[edd]

An eV is not a unit of energy divided by c^2.

I think MattusMaximus pretty obviously made some unintended errors. He does know what he meant to say, fairly clearly.

 

[BenBurch]

I think MattusMaximus pretty obviously made some unintended errors. He does know what he meant to say, fairly clearly.

Two commas would have fixed it anyway.

 

[Soapy Sam]

I had an email from my mother (aged 86) asking me what I thought of all this. I passed on some of the comments from here. Her view- " If it takes less time than it should, then the distance must be shorter than they think. Watch this space."

I suspect she may be right on the money. As usual.

 

[MattusMaximus]

Two commas would have fixed it anyway.

Yup, stupid grammar.

 

[Lennart Hyland]

Thanks for your answers guys!

 

[Tim Thompson]

Superluminal Neutrinos III

I have noticed several pre-prints that have cropped up addressing the OPERA superluminal neutrinos and thought I would post a brief summary of what I see. I quote snippets directly from the papers where it is worth while and add a few comments of my own. In all cases a PDF of the paper can be had by following the arXiv link.

It's possible for group velocities to exceed c - there's nothing even slightly exotic or surprising about that. {...} While the recent result might be explained by something related to group velocities (for instance, the proton pulses are quite wide, and "when" they first hit the graphite block is hence not very well defined), if that is the explanation it does not mean that neutrinos propagate faster than c.

That's actually what I was thinking of. Since I am not familiar with the exquisite features of particle physics, I am temporarily free to speculate in unrestrained fashion. I was wondering if what we are seeing could be the group velocity of the neutrinos.

This seems to be an idea that is catching on.

Neutrinos superluminality and Local Lorentz Invariance; Cardone, Mignani & Petrucci; 24 Sep 2011.

In those experiments, where a time of flight is measured, there exists two types of superluminality. The first type has to do with the temporal width of the signal (in our case, the width of the bunch of neutrinos) and hence with the performance of the detectors. This first type is not a genuine superluminality. The second type is related, conversely, to the limit of the parameter δ.

This parameter δ represents the breakdown of local Lorentz invariance. The authors show that this parameter for the OPERA data has a value on the order of 10^-5, which compares to published results that range from 10^-8 to 10^-4 and are therefore not sufficient to claim a violation of local Lorentz invariance. So the most likely explanation is the pulse width, consistent with the idea that this is a group velocity effect.


Fast light, Fast Neutrinos?; Kevin Cahill; 25 Sep 2011.

Light has been observed with group velocities both faster and slower than the speed of light. The recent report from OPERA of superluminal 17 GeV neutrinos may describe a similar phenomenon.

Cahill calculates the group velocity in a medium with complex index of refraction and points out that OPERA might have discovered "fast neutrinos", with group velocities in excess of the speed of light due to a resonance with earth's crust matter near 17 GeV.


On the report of discovery of superluminal neutrinos; Moses Fayngold, 26 Sep 2011

In this brief comment we argue that even if the superluminal neutrinos do exist, this fact by itself will not overturn relativity.
{ ... }
The recent report about the discovery of µ-neutrinos' superluminal propagation in the CERN-OPERA experiment [6] may be based on some subtle systematic error. For instance, it could be another case of observed superluminal group velocity similar to those discussed in [1-3]. This is possible because the earth's crust acts as an optical medium with refraction index n which is extremely close but not exactly equal to 1 and thus can reshape the pulse associated with each particle.

Fayngold goes on to point out that some studies suggest a tachyon duality, where the normal "tardyons" are each partnered with a tachyon of the same invariant mass, spin, charge & etc. The failure thus far to find charged tachyons can be the result of random deflections due to quantum Cherenkov radiation, which will not happen with neutral particles. Hence, the OPERA results could point towards the discovery of a tachyon dual particle. That, of course, is far more exotic, and arguably less likely, than the more mundane idea of a group velocity effect. Still, this idea too seems to have legs.

But first, as has already been pointed out, we have neutrinos from SN1987A which certainly did not propagate that much faster then light.

Inconsistency of super-luminal Opera neutrino speed with SN1987A neutrinos burst and with flavor neutrino mixing; Daniele Fargion, 25 Sep 2011

Fargion points out that the observed SN1987A electron neutrino burst establishes the constraint that all neutrinos cannot be tachyonic in nature, but points out that if µ-neutrinos are tachyonic but e-neutrinos are not, then the SN1987A data and the OPERA data could be mutually consistent. The next paper make that consistency more quantitative.

Apparent Lorentz violation with superluminal Majorana neutrinos at OPERA?; Tamburini & Laveder, 28 Sep 2011 (version 3, version 1 dated 26 Sep 2011)

{ ... } we suggest a simple toy model that describes these neutrino states as a Majorana-like particle with an imaginary mass component lower limit on the order of 10^-13 eV and, for p ≤ kc, in the limit p ~ kc, an imaginary mass on the order of 10⁸ eV, if the data interpretation and Monte Carlo simulations of OPERA results are correct. This solution, already discussed by Majorana in 1932, has here the meaning of a phenomenological description of what has been observed without invoking Lorentz invariance violations due to quantum gravity effects, discarded by the most recent results present in the literature. This apparent tachyonic propagation, also supposed for v_e's in SN1987a data [4] an be due either by an actual Majorana property of neutrinos, or through MSW mixing, sterile neutrino states and acquisition of orbital angular momentum states, induced by the structured material in Earth's crust. We argue that this superluminal effect is expected only in the presence of neutrinos interacting with matter, with an effect similar to that observed with photons in a metamaterial [8]. in vacuum, instead, neutrinos are expected to propagate at speed less or equal than the speed of light, otherwise the anticipation observed in the SN1987a would have been of years.

Another paper along similar lines requires the presence of a propagating medium, but appeal to radiative corrections in the particle-vacuum interaction, due to the presence of the propagating medium. So the presence of matter is still required, but it is now the interaction between the neutrino and the vacuum, not the matter, that induces superluminality.

Neutrino dispersion relation changes due to radiative corrections as the origin of faster-than-light-in-vacuum propagation in a medium; Karl Svozil, 25 Sep 2011

Radiative corrections to the dispersion of neutrinos in nonstandard vacuum may give rise to "boosts" in their speed. This could explain recent experimental evidence by the OPERA collaboration, as well as the null result indicated by the supernova 1987A (SN 1987A) measurements of neutrino and photon arrival times
{ ... }
In summary we have discussed field theoretic options for the "speedup" of ultrarelativistic particles beyond the speed of light barrier in the presence of suitable media which cause a reduction of polarizability and radiative corrections. These considerations do neither represent the possibility to circumvent relativistic causality, because no ad-hoc "willable" superluminal information or paradoxical time travel will be rendered [32]; nor are they inconsistent with the present formalism of relativity theory or the theory of quantized fields; on the contrary they can be taken as a demonstration of the relativistic formalism [33, 34]. They would not even make necessary the standard SI conventionalization of the constancy of the speed of light [35]; with the possible addendum of referring to this the velocity of light in a particular type of rather idealized vacuum.

The next paper ignores the propagating medium altogether. Here is is purely an interaction between the neutrino and the vacuum, but it's an interaction (a dispersion relation) that literally switches on & off as a function of the neutrino mass (could be total mass energy, not clear to me). This allows for the low e-neutrinos from SN1987A to remain subluminal, while the µ-neutrinos from OPERA cut loose.

Beyond the speed of light on Finsler spacetimes; Pfeifer & Wohlfarth, 27 Sep 2011

Taking the OPERA result seriously hence tells us that the structure of spacetime cannot be described simply by Lorentzian Geometry

Finally, the last paper simply asserts that there is nothing "real" here at all. The apparent superluminality is just that, apparent, and due to the statistics of the neutrino distribution, and the fact that only about 10⁴ neutrinos from about 10²⁰ target protons are detected. A strongly damped Gaussian wave packet describing the neutrino distribution will produce the appearance of superluminality.

Possible statistical mechanism of anomalous neutrino velocity in OPERA experiment?; Robert Alicki, 26 Sep 2011

That's what I have seen come across the desk so far. Could be the group velocity, could be tachyonic particles, could be weird particle-vacuum interactions, or it could be a statistical artifact of the data. There are champions for all sides.

 

[Soapy Sam]

Can someone explain the concept of "Group velocity" in idiot speak, please?
If I substitute ball bearings for neutrinos , I can see that shooting a bunch out of a magnetic cannon, there will be a spread of muzzle velocities. So a 1 second burst will hit the target spread over more than 1 second.
What I don't see is how any of them can get there faster than Distance/ Muzzle Velocity (ignoring air resistance or other energy loss).
ie the average velocity will be lower than the highest muzzle velocity in all cases. Never faster.
In the case where the muzzle velocity= c, some neutrinos can be expected to arrive late, but not early.

Is it possible to put a second neutrino detector (hey- it's only money) about ten feet downstream of the graphite source, to see if any of them are leaving the source at unusual speed? That would rule out the 473km variable.

Just thinking about this, - is the idea of group velocity to do with the possibility that one of the last shots fired may be miscounted as one of the earliest arrivals? If so, would thespread time per "burst" not be pretty consistent from shot to shot and so easily corrected for?

 

[MattusMaximus]

I have noticed several pre-prints that have cropped up addressing the OPERA superluminal neutrinos and thought I would post a brief summary of what I see. I quote snippets directly from the papers where it is worth while and add a few comments of my own. In all cases a PDF of the paper can be had by following the arXiv link.

Thanks for all the info, Tim. Going to be a LOT of interesting reading in the weeks to come

Having said that, I think much of what's in those papers looks to be speculation (which is fine; I had also speculated on the group velocity question). What's going to be really interesting to see is when other research groups attempt to replicate the results!

 

[MattusMaximus]

Can someone explain the concept of "Group velocity" in idiot speak, please?
If I substitute ball bearings for neutrinos , I can see that shooting a bunch out of a magnetic cannon, there will be a spread of muzzle velocities. So a 1 second burst will hit the target spread over more than 1 second.
What I don't see is how any of them can get there faster than Distance/ Muzzle Velocity (ignoring air resistance or other energy loss).
ie the average velocity will be lower than the highest muzzle velocity in all cases. Never faster.
In the case where the muzzle velocity= c, some neutrinos can be expected to arrive late, but not early.

Is it possible to put a second neutrino detector (hey- it's only money) about ten feet downstream of the graphite source, to see if any of them are leaving the source at unusual speed? That would rule out the 473km variable.

Just thinking about this, - is the idea of group velocity to do with the possibility that one of the last shots fired may be miscounted as one of the earliest arrivals? If so, would thespread time per "burst" not be pretty consistent from shot to shot and so easily corrected for?

First of all, stop thinking about neutrinos as little ball bearings. A better way to think of them in this context is like small wave bundles; this is due to wave-particle duality. The group velocity is the speed at which the envelope of such a spread out wave bundle travels. Link

 

[dasmiller]

Can someone explain the concept of "Group velocity" in idiot speak, please?
If I substitute ball bearings for neutrinos , I can see that shooting a bunch out of a magnetic cannon, there will be a spread of muzzle velocities. So a 1 second burst will hit the target spread over more than 1 second.
What I don't see is how any of them can get there faster than Distance/ Muzzle Velocity (ignoring air resistance or other energy loss).
ie the average velocity will be lower than the highest muzzle velocity in all cases. Never faster.

Sticking with your BB analogy, let's assume that all the BBs move at 50 m/s, we have a 100 meter path, we start our stopwatch when the middle of the burst goes past the starting line and stop it when the middle crosses the finish line:

So, the stopwatch showed 2 seconds elapsed for 100 meters, avg speed is 50 m/s, all is good.

Now, let's suppose we add an evil electromagnet to the path:

"Wowser!" you might say. "Adding the evil electromagnet increased the average speed from 50 m/s to 62.5 m/s! Sure, we lost some BBs, but that's a small price to pay."

But, of course, none of the BBs went faster than 50 m/s.

Group velocity tricks are like that, only with waves.

(someone who actually understands physics should probably correct me here, but at least it's an easily-understood falsehood)

ETA: Yeah, it doesn't explain phase vs. group velocity, but it does sort of show the 'trick.'

 

[Soapy Sam]

Thanks for both of those, guys.
I get the BB demo- but surely the fact the total duration of the detected burst is half the length of the fired burst would set bells ringing?
I'm off to follow MM's link.


ETA- EEEK! That makes my eyes go crossed. I think I get it. Thanks.

 

[dasmiller]

deleted

 

[Drachasor]

Group velocity tricks are like that, only with waves.

Granted, but they did account for that, unless there's something about the situation they didn't understand. They also accounted for the statistical distribution of the individuals impacts (which is a much bigger issue). Unless there was some unknown problem going on.

 

[SusanB-M1]

Thanks for both of those, guys.
I get the BB demo- but surely the fact the total duration of the detected burst is half the length of the fired burst would set bells ringing?
I'm off to follow MM's link.


ETA- EEEK! That makes my eyes go crossed. I think I get it. Thanks.

Ditto - also thanks for #347!

 

[rjh01]

Science youtube on the subject from my favourite channel

 

[MattusMaximus]

I finally got around to reading the CERN-OPERA paper and Costella's retraction of his earlier criticism of the statistical analysis, and I have to say - wow! I found the "Palmer method" of analyzing the data sets to be a really good visual way of showing the statistical significance of the data. Hell, it is so easy to see what's going on using Palmer's approximation method that I might even share this sometime in the near future with my AP students. Maybe I'll also pass it along to the math teachers who teach the statistics courses

Now, if I can only find some time this weekend to watch the video of the seminar... and read up on some of those papers Tim linked to above...

 

[MattusMaximus]

Thanks for both of those, guys.
I get the BB demo- but surely the fact the total duration of the detected burst is half the length of the fired burst would set bells ringing?
I'm off to follow MM's link.

ETA- EEEK! That makes my eyes go crossed. I think I get it. Thanks.

Welcome to the world of modern physics, Sam

 

[Soapy Sam]

In other news...http://www.bbc.co.uk/news/science-environment-15079119

 

[Myriad]

This thread is for discussion of the CERN-OPERA neutrino findings. As the possible implications cover a broad range of modern physics, particle research, statistics and so forth, it could be a rather diverse subject. Nonetheless, arguments about scientists covering up glaring errors in Relativity theory belong in the other thread which is in Conspiracy Theories. Please stay on topic.

Replying to this modbox in thread will be off topic  Posted By: Myriad

 

[Anders Lindman]

This thread is for discussion of the CERN-OPERA neutrino findings. As the possible implications cover a broad range of modern physics, particle research, statistics and so forth, it could be a rather diverse subject. Nonetheless, arguments about scientists covering up glaring errors in Relativity theory belong in the other thread which is in Conspiracy Theories. Please stay on topic.

Replying to this modbox in thread will be off topic  Posted By: Myriad

Ok, but I suggest people should look into the claims of Einstein's relativity before taking it too much as a gospel. I sense an unusual amount of confusion among people, even among physics experts, about something that should be pretty basic.