Why do all measurements of neutrino speed show a positive delta t?

[Niceperson27]

Hi people,

I have the following question:

First, here is a concise statement of the major neutrino speed measurements:
http://en.wikipedia.org/wiki/Measurements_of_neutrino_speed

As you can see all of them show that the speed of neutrino is within the speed of light, when taken into consideration the errors of course. But if you notice, almost all the measurements (MINOS (2007), OPERA (2011, 2012), ICARUS (2012), Borexino (see: improved analysis), LVD, Icarus, Opera) provide a positive δt (when no error is accounted for). Note that δt>0 indicates an earlier neutrino arrival time.

Shouldn't be that almost half of the measurement should provide a positive δt and half of them a negative one? I mean it does not make sense statistically.

Thanks

 

[Dale]

You would need to approach this with a formal meta-analysis. Usually in meta-analysis it is not simply a vote-counting approach, but the weighting is determined roughly by the inverse of the variance. So if you have a large number of high variance studies with a positive δt and a small number of low variance studies with a negative δt then you may still get a negative δt in the meta-analysis.

I don't know that anyone has done such a study, but it would be interesting.

 

[Niceperson27]

Sure,

but if you take a look at the variances you will see that only negative \delta t is for MINOS 2012 (new timing system, where they improved the measurements of the previous old one), where the variance is in fact quite small.

Of course we would need more measurements (than the 5-6 we have) to see what's going here, but remember something IMHO: I do not think we are over yet with the ''faster than light'' issue.

 

[phinds]

Sure,

but if you take a look at the variances you will see that only negative \delta t is for MINOS 2012 (new timing system, where they improved the measurements of the previous old one), where the variance is in fact quite small.

Of course we would need more measurements (than the 5-6 we have) to see what's going here, but remember something IMHO: I do not think we are over yet with the ''faster than light'' issue.

So, you think neutrinos travel faster than light?

 

[Niceperson27]

I did not say that. I mean that I do not think that the scientific community has stopped discussing on this issue.

 

[Dale]

only negative \delta t is for MINOS 2012 (new timing system, where they improved the measurements of the previous old one), where the variance is in fact quite small.

So that one will be given the strongest weight.

 

[Vanadium 50]

The best measurements are from SN1987A. These are about a thousand times better than the other measurements. I don't think you learn anything by looking at measurements 1000x worse and seeing how they are distributed. At best, that tells you something about the systematics of inferior measurements, not anything about nature.