## Tuesday, September 20, 2011

### Rumour of the Century

We don't usually report on unsubstantiated rumours here at AP, but this one is just too spectacular to ignore. Jester thinks its crazy, Phil sounds excited, and Graham says that Tommaso had a post up with a $6.1 \sigma$ result from OPERA, but the post has now disappeared. Given the number of false rumours that get circulated, we should be doubtful at this point. Here is OPERA's last arxiv paper. The CERN seminar is this coming Friday.

So the rumour is that neutrinos arriving at OPERA have travelled at a speed greater than $c$. Forget fairy fields. If this is true, it demolishes establishment thinking in one falcon swoop. Could the minus sign in Brannen's Koide relation for neutrinos be responsible for such tachyonic behaviour? Why not? Or, perhaps all neutrinos are tachyons. Now the minus sign goes with the lightest neutrino mass state. The literature has an annoying tendency to confuse EW and mass states, but we should note that all mass states can occur in $\nu_{\mu}$-$\nu_{\tau}$ oscillations.

1. As we know, photons always travel at $c$ locally. Particles with mass, such as electrons and muons, travel at speeds less than $c$ precisely because they have mass. But until OPERA, as far as I know, nobody could actually measure neutrino speeds. And we already know that the Koide formula looks different for neutrinos. The tachyonic behaviour would not even violate Lorentzian geometry, because we would simply insist that tachyons always travel at speeds greater than $c$.

2. Even kneemo likes tachyons, because M theory has tachyons.

3. And it would strengthen the argument that the neutrino sector is crucial for understanding gravity.

4. So now we can rethink the strange MiniBooNE/LSND results, and in fact all the appearance disappearance anomalies. With tachyonic neutrinos, hopefully the ad hoc introduction of sterile states can finally be dismissed. As we said some time ago, the local neutrino gas should not behave in a standard fashion.

5. I predict that the rumored result will not stand.

6. Of course you do, Mitchell. You are still a string theorist. But there is no reason to doubt that tachyons exist in our form of M theory. Mind you, I bet OPERA will have a hard time convincing everyone that they know what they are doing.

7. Now according to the rumour, which contains only the sketchiest facts, the OPERA detector was looking for the onset of tau neutrinos from a well timed $700+$ km beam. This strongly suggests that ALL the arriving neutrinos are travelling at a speed $> c$. Duh.

8. So all mass states are tachyonic.

9. Some people are already talking about the implication of classical time travel, but there is no reason to jump to that conclusion here. There is nothing concretely acausal about sending the neutrinos from point A to point B and then measuring the apparent speed. The speed is whatever it is. Relativity is prefectly well respected by tachyons, even in interaction with ordinary matter, provided we consider a complexification of our geometry, which we do with twistor theory anyway.

10. No, wait! The onset time only gives an indication of the fastest speed. It is not true that all neutrinos need travel that fast. So perhaps OPERA actually sees something really amazing, like a triplet of arrival times, one $>c$.

11. And since the fastest speed corresponds to the lowest energy for a tachyon, the low energy excess of MiniBooNE comes from the most tachyonic neutrinos.

12. My understanding of Carl's philosophy of time is that time is absolute and Lorentz symmetry is emergent. I don't know how yours works. I don't know how to "interpret" just two timelike dimensions, let alone three. When you have a two-time signature for twistors, that's not something which shows up in any observable physical state; it's something that you analytically continue back to the physical signature. Similarly, when you have multiple times in F-theory, S-theory... they have to be hidden away with the spacelike compact dimensions. At some point, the formal mathematical concepts of time that are employed in physics have to reconnect with phenomenological time, and I do not at all see how that is possible if you have more than one "time".

13. It smells a bit bad, and rather inconsistent with previous data...

There had been a delay of ~3h between the neutrinos and the gammas in SN1987A (it had been explained by astrophysical reasons, though). If one however interprets it as physical, takes the distance of the SN (168000 ly) and rescales it to the distance (700 km) between CERN and the Gran Sasso (GS), one would expect

Dt ~ 10000 s * (700e3/(168000*3e7*3e8)) ~ 5 ps

which is 1 millimeter of delay... It is true that the SN neutrinos were in the MeV, but it looks strange that something dramatic happens between the MeV and the GeV...

There was also a ~1-day-before claim in 1987, but then it was withdrawn - and in any case it is 2-3 orders of magnitude below the needed sensitivity.

Alessandro De Angelis

14. If it is true, it would mean that neutrino can see more than any other particle. Wow. In a fundamental theory of quantum gravity c is no longer an invariant, the planck lenght or certain fundamental lenght \alpha L_P is the main quantity. Anyway, I hope this could be true. LHC is being something boring yet...The surprinsing discoveries are yet to come! Careful has to be paid to the tachyonic conclusion. OPERA is not a vaccum detector, so a bad definition of group speed in the dispersion relation could appear as a fake v>c. Is the rumour on OPERA a claim on neutrino speed at vaccum? Curiously, it is an experiment I am following less than others. And about a theory with v>c...I only know three theories ( at least published) that could obtain that claim (forget M theory at principle): Gonzalez-Mestres theory of superbradyons, varying speed-of light theories and extended relativities in C-spaces. Of course, they are non main stream theories, but they postulate from first principles the possible existence of particles with v>c without tachyons. I would like to emphasize this: if it is true, if neutrino has v>c at vacuum, it does not necessarily means they are tachyons. Questions: has someone else realized what would happen if there some other EM-like in the Universe very weakly coupled to the SM and whose "speed of light" is NOT the common speed-of-light?

15. Yes, the supernovae data are interesting, but it could be the case that the tachyonic species are only observable more locally.

Juan, many people have thought about these kind of things, since the 1950s. However, very few people think about emergent geometry using modern mathematical methods, with which far more is possible. I have no more information on the rumour, since I did not even get to read Tommaso's post. I don't think the rock medium is an issue, since it is pretty transparent to neutrinos. My guess is that a satellite measurement of the distance, using an accurate angle for the two photon paths, could be used to determine a length for the other side of the triangle, as a reasonable estimate of the distance.

16. Graham knows more about supernovae. And someone at vixra mentioned fibre optics 'down the shaft' from the GPS point.

17. Now we just have to wait. As Graham says, the mistrust of $6.1 \sigma$ results is rather disturbing to those theorists that approve of the result.

18. Like EPR, till they show what really they have got, we only get romours...A pity!What time is the Friday talk, local time? I am getting interested since there are several prominent blogs commenting the rumour. Will it be real after all?
Yeah, I know neutrino is almost transparent to medium ( I am doing my Master thesis on neutrinos) but group velocity and phase velocities can be greater than c. I have to read more about what they are measuring, if it proves to be a real 6.1 sigma claim.

19. By the way: note that something weird is also happening in the existent data on reactor neutrinos. Will the neutrino surprise us ...again? :D

20. Has anyone thought of the possibility of a tunneling-like event in the 'insides' of earth? It is a well known fact that light CAN travel faster than c in case of a tunneling event. (Steinber, PRL 1993 - http://prl.aps.org/abstract/PRL/v71/i5/p708_1 - Or just google 'tunneling time of single photon') In thet perspective, this data would not mean tachyonic behaviour of neutrinos, but simply the occurence of quantum barrier for the neutrinos. Just saying it...