Neutrino Data Could Spell Trouble For Relativity

Science News has an exploration of the deeper implications of neutrino oscillation, one experimental confirmation of which we discussed last month. "The new findings could even signal a tiny breakdown of Einstein's theory of special relativity. ... MINOS [for Main Injector Neutrino Oscillation Search] found that during a 735-kilometer journey from Fermilab to the Soudan Underground Laboratory in Minnesota, about 37 percent of muon antineutrinos disappeared — presumably morphing into one of the other neutrino types — compared with just 19 percent of muon neutrinos. ... That difference in transformation rates suggests a difference in mass between antineutrinos and neutrinos. ... With the amount of data collected so far, there's just a 5% probability that the two types of particles weigh the same."

Comments

statistics fail

[gumbi west]

From the article, "there’s a 5 percent probability that the two types of particles weigh the same." Except, that would require a Bayesian statistical analysis and a prior. The thing to remember about confidence intervals is that the interval is random while the true value is stationary, so if you want to make statements about randomness, you have to make statements about the interval. Example, "An experiment conducted this way would find more muon antineutrinos than muon neutrinos disappear 95% of the time."

Re:statistics fail

[Parlyne]

The correct statistical statement here would be that an experiment like this one would show a splitting between particle and anti-particle properties at least this large 5% of the time even if there were no difference at all.

CPT = Lorentz Invariance

[SciBrad]

If I recall correctly CPT presumes the correctness of Lorentz invariance. And Lorentz invariance is one of the bedrocks of relativity. In other words CPT comes about from assuming your theory is Lorentz invariant and if CPT were violated it would mean Lorentz invariance is violated as well (check out Physical Review Letters 89: 231602 by Greenberg, O.W, which shows CPT violation implies Lorentz violation).

Re:CPT = Lorentz Invariance

[JoshuaZ]

It's a lot easier than tossing out your beloved theory or trying to build it up from scratch based on solid scientific evidence to support each individual tenet. I think the latter is what needs to be done, but it will take time. We need to re-figure out what we know absolutely. IOW, what aspects of special relativity are not contradicted by a CPT violation? If the Lorentz Transformation is called into question then so is science fiction's much beloved time dilation And what about the Twins Paradox? Yikes.

Time dilation has been observed in a number of different contexts, most famously by putting atomic clocks on airplanes and measuring the resulting slow down as they fly around the globe. Even if SR fails, time dilation is still an experimentally verified fact.

Re:CPT = Lorentz Invariance

[Parlyne]

Lorentz covariance means that a quantity changes in a way given by the appropriate Lorentz transformations under boosts or rotations. Lorentz invariance means that a quantity is unchanged under boosts or rotations. So, Lorentz invariance is a subset of Lorentz covariance which applies to frame-independent quantities like proper time, electric charge, or rest mass. As for explaining these results, I think you'll find that a large majority of particle physicists (both theorists and experimentalists) will tell you that a 95% confidence level is actually very low. It means that a value (here something characterizing the difference between neutrinos and antineutrinos) differs from 0 by only twice the uncertainty in its value. In particle physics, its usually a bad idea to trust a result until there's enough data that deviation from 0 is at least five times the uncertainty in its value. (In fact, there have been cases where effects that had deviations from 0 of about 4.5 times their uncertainty that still turned out only to be statistical flukes.) But, those uncertainties tend to decrease in such a way that the uncertainty multiplied by the square root of the number of data points you're calculating the value from stays constant. So, this is rather slow to attain. If, however, with a great deal more data, this effect still seems to be there, there are still some ways out. Essentially, you have to posit that somewhere between the production of the neutrino and its detection there's something unaccounted for which treats neutrinos and antineutrinos differently. Maybe there have been details overlooked about how propagating through matter (rather than antimatter) affects neutrinos (although this seems unlikely). There's also a paper I've run across recently which suggests that the standard treatment of neutrino oscillations misses a small dependence on the details of the physics by which the neutrinos are detected. (Personally, I'm waiting for people who know quite a bit more about quantum measurement and about neutrino oscillations to weigh in on this one.) It's only once everything of this sort has been ruled out that we face the prospect of actual, honest-to-goodness CPT violation.

Re:CPT = Lorentz Invariance

[TapeCutter]

"Time dilation has been observed in a number of different contexts"

Indeed! Without taking time dialation into account GPS locations would systematically drift about 10km/day.

CPT Symmetry

[DrJimbo]

The fine article said:

If the interactions of particles are thought of as a movie, CPT symmetry requires that whatever physics occurs during the show must be the same whether the film is run forward or backward (time), viewed through a mirror (parity) and repopulated with each particle being replaced by an antiparticle (charge).

This is unclear at best. CPT symmetry says that when the film is run backward AND seen through a mirror AND all particles are replaced with the anti-particles (and vice versa) then the physics should be the same.

If you change just one, for example by running the film backward but without the mirror or the the particle exchange, or if you change two, for example, running the film backward and with the mirror but no particle exchange, then the physics will change.

Re:I think I had an astronomy prof that talked abo

[ultranova]

That a theory is just a tool for understanding and predicting reality.

But a theory is more than just that, it's a mental model of reality, the context for sensory input. Einstein's General Relativity and Newton's Laws of Motion are fundamentally different: Newton took time and space to be a passive background, while Einstein made spacetime an active participant in events. The two theories don't just differ a little bit on their results, they represent fundamentally different ways of looking at reality.

But in a way your professor was right: a theory is "just a" tool for understanding reality, in the same way as you brains "just" allow you to think.

Re:Newton's laws would be a great example

[JSBiff]

Oh, one other point - a large part of why we teach them in High School and basic undergraduate physics classes is that they don't require a lot of math beyond algebra and trig, and maybe a little calculus (some knowledge of integration and differentiation can still be useful even with Newton's Laws), but when you start looking at the more accurate models of relativity and things, it starts to take knowledge of much more advanced math, which High School students and undergrads(well, most of them anyhow) won't know or understand.