Neutrino oscillation observed

[sjastro]

One of the early problems with the solar nuclear fusion model was that the observed neutrino flux reaching Earth was only one third the theoretical amount.

This was explained by neutrino oscillation where a neutrino could change "flavours" and oscillate between an electron, muon and tau neutrino.

While neutrino oscillation has been observed in solar neutrinos, it has never been observed in experiments..... until now.

http://news.discovery.com/space/ferm...ge-110704.html

Regards

Steven

[renormalised (Carl)]

Very important discovery, now that neutrino oscillation has been experimentally confirmed (well, at least to 3 sigma).

[CraigS]

Correct me if I'm mistaken, but 3 sigma means that there is about a 1 in 1,000 chance that the result can be attributed to a statistical fluctuation in the data, right (??)

It seems that in particle physics, 3 sigma creates 'interest', but everywhere else (generally), 5 sigma, (~ 1 in 1 mill chance that the result is a fluke), is needed to claim a discovery.

Recently, (in June), Femilab reported a possible new particle had been discovered but when checked by a second detector, they found slightly less than the 5 sigma level, so the new particle announcement was deemed not valid.

So in these guys' words:

With more data, the current 3-sigma signal should strengthen sufficiently to claim a solid discovery.

Hmm … maybe …
5 sigma seems to be what they need in order to make the ultimate claim of 'discovery' ..

Cheers

[sjastro]

Justification for 5 sigma level.

Ever since, the role of statistics, and the justification of the 5σ confidence level, have been major topics in particle physics. For example, Oxford University physicist Louis Lyons organized a workshop on the subject at CERN in 2007, and he plans another one on the same topic at CERN early next year. The workshop proceedings reveal just how rich and sophisticated a field the application of statistics to physics has become (see the webpage).
In 2008 Lyons wrote an article, "Open statistical issues in particle physics" (arXiv:0811.1663v1), that included a section entitled "Why 5σ?". While statisticians invariably say that being so stringent is overkill, Lyons writes, there are several good reasons for it. One is past experience. As he points out, "we have all too often seen interesting effects at the 3σ or 4σ level go away as more data are collected". A second is the "look elsewhere" effect: the decisions you make in sorting the data into "bins" in a histogram may serve to concentrate fluctuations, meaning that "the chance of a 5σ fluctuation occurring somewhere in the data is much larger than it might at first appear". Finally, physicists worry that some systematic effect may have been underestimated or even missed altogether.
Nevertheless, 5σ is essentially arbitrary, with many discoveries accepted with considerably less sigma, and some not accepted even with higher sigma. The classic recent instance, numerous respondents reminded me, is the still-disputed claim, made several years ago by the DAMA/LIBRA experiment at the Gran Sasso National Laboratory in Italy, of evidence for the presence of dark-matter particles in the galactic halo at a confidence level of 8.2σ (arXiv:0804.2741). No-one doubts that DAMA has seen something. But the fact that other experiments have not seen anything – even though they should if DAMA did – raises doubts about DAMA's interpretations, as did a certain chariness by the collaboration about sharing information. The "DAMA effect" underscores that statistics alone do not make a discovery.
One factor is that the translation of sigma into a probability often involves the assumption of a normal distribution of errors. "It is by no means clear how to justify this assumption in many cases," Charles Jenkins from CSIRO in Canberra, Australia, told me. "And it is certainly not clear that the assumption of normality applies so far out in the wings of the distribution. If we had enough data to draw a histogram and verify the error distribution out to 5σ, we probably wouldn't be bothering with statistics!" Scientists insist on this apparently extreme level of significance, Jenkins continued, as "an insurance policy against the multitude of error sources that don't average away quickly and give fat tails to the error distribution". It is, he continued, a cheap and cheerful way of dealing with the underlying issue, which is that ascribing the significance level to an observation requires an assumption about the error distribution. "One has to view a result as a package," he wrote, "where the statistical interpretation is one of the things that may be wrong. As a fellow student of mine once asked in a seminar, 'What are the errors on your errors?'."
The critical point
Few respondents were excited about the CDMS-II results. "If you roll a dice six times," says astrophysicist Rafael Lang from Columbia University in the US, "would you be excited if you rolled the 'four' twice?"
Nearly everyone I spoke to had tales – many well known – of signals that went away, some at 3σ: proton decay, monopoles, the pentaquark, an excess at Fermilab of high-transverse-momentum jets. Several people reminded me of one case from the story of dark energy – what is believed to be causing the expansion of the universe to accelerate – when Saul Perlmutter and colleagues (Astrophys. J. 483 565) concluded that the mass density (ΩM) of a flat universe was about 1 (and the cosmological constant Ωλ ~ 0) based on their first seven supernovae. This result was, however, 2.3σ away from their later answer, although the inclusion of more supernovae data could have made a big systematic difference.
Some of these tales – such as the latter – were the result of statistical fluctuation. Others, however, were due to faulty analysis. The need to protect against that is, I think, the reason for the otherwise absurdly high confidence level. "The fact is, in high-energy-physics experiments, you sometimes find substantial systematic errors," says Grannis. "The big fear is: how do I know I have thought of all sources of error?"

Regards

Steven

[renormalised (Carl)]

The problem with being so stringent in the level of confidence is that nature itself doesn't work in that way. Scientists maybe missing discoveries simply because they don't meet the required levels of statistical analysis. Nature can be very quirky and never plays by the book. Things can crop up unexpectedly and then disappear off the charts. All the experiments in the world may not show another result.

However, in playing it safe with such stringent conditions of acceptability, it does negate to some extent the possibility of false positives and the like. But, how far do you have to go, especially when even higher levels of confidence have been rejected in the past. Where/when do you call a discovery 100% certain??. Especially in particle physics, where a spray of particles at the detector of an accelerator can number in the billions, what are your chances of finding anything even at 5 sigma??!!. Then again you may find something right off the cuff. Or repeat your experiments and not find it again. If you follow chaos theory, it would be almost impossible to repeat your experiments exactly, in any case. So how do you rate the results then??. The statistics would be meaningless.

You can see why they use such a high confidence level for the confirmation of a discovery, but it's still not the ideal way of going about it. What's needed is a symposium on this matter and a set of guidelines ruled upon that can be used across all disciplines. That way, at least we could be more confident of smoothing things out a little better than what is being experienced at present.

[CraigS]

Hmm .. great article, Steven .. many thanks for that.

A fascinating topic (although, somewhat off-topic .. apologies).

I've been pondering all this stuff over the last few days.

The sigma levels (and other considerations) are important, as they do lead us to regard things as having the status .. of say: 'a primitive physical object', (requiring demonstration that they exist in the lab), as opposed to something having the status of say: 'a concept', which allows us to continue thinking that the Standard Model is still Ok. For eg: the Higgs boson still doesn't have the status of a primitive physical object yet, eh?

I think that this is yet another aspect where much confusion exists outside of scientific circles, and creates a lot of trouble when scientific 'discoveries' hit the mainstream media.

Relativity doesn't have the same status as say an electron .. but it is still a big enabler of extended scientific thinking …

Coming back to the original topic though, if these neutrino oscillations turn out to be agreed as being physically real, then I'd imagine this would put the onus on those who refute fusion as the source of the Sun's energy, to come up with a viable alternative, eh?

Cheers

[renormalised (Carl)]

In relation to my last post, yes, you could use Bayesian analysis but what would be the point. Considering its inherent subjectivity, your results would be biased right from the start. Assuming the prior conditions of the statistical set is just as accurate as saying "the milkman did it". Given that the number of assumptions one can make about the priors of any analysis, you might as well use "the milkman did it" because everyone with an opinion on what initially happened could make an analysis and get what they wanted out of it. And, that's with exactly the same set of values!!!.

That's why I believe we have to be careful with using statistics. It can be made to say or justify anything. If it were as unambiguous as algebra or calculus, for example, then there would be no problem. But it's not.

[renormalised (Carl)]

Originally Posted by CraigS

Hmm .. great article, Steven .. many thanks for that.

A fascinating topic (although, somewhat off-topic .. apologies).

I've been pondering all this stuff over the last few days.

The sigma levels (and other considerations) are important, as they do lead us to regard things as having the status .. of say: 'a primitive physical object', (requiring demonstration that they exist in the lab), as opposed to something having the status of say: 'a concept', which allows us to continue thinking that the Standard Model is still Ok. For eg: the Higgs boson still doesn't have the status of a primitive physical object yet, eh?

I think that this is yet another aspect where much confusion exists outside of scientific circles, and creates a lot of trouble when scientific 'discoveries' hit the mainstream media.

Relativity doesn't have the same status as say an electron .. but it is still a big enabler of extended scientific thinking …

Coming back to the original topic though, if these neutrino oscillations turn out to be agreed as being physically real, then I'd imagine this would put the onus on those who refute fusion as the source of the Sun's energy, to come up with a viable alternative, eh?

Cheers

That wouldn't worry them in the slightest, especially the EU nutters. They'd more than likely have a "solution" for the "problem" even as we speak. Probably that the neutrino doesn't exist and/or some hair brain idea about electrical charge of subatomic particles.

Speaking of "status" of objects...I've just come up with a couple of terms. Those objects which have experimental, empirical proof we could call "pragmatic", and those that are strictly theoretical, "romantic"

I pretty certain you're right in saying that the confusion between what science and scientists deem as being proof and what the great unwashed deem as being proof, are two entirely different sets of criteria and that the confusion exists. The main fault in the interpretation here is coming through the journos, simply because it's hard enough for the scientists to arrive at a consensus as to what is proof let alone having complete numpkins like journos then figure out what's proof and report it to the rest of us. Filtering the definition of scientific proof through the express desire of wanting to sell a story, is not the way of going about reporting science. The major irony is that if you were to report the science strictly as is, few in the general public would be able to follow it. Except those that might have some training in science and/or be intelligent enough to figure it out in any case.

[CraigS]

Carl;

Who said anything about Bayesian Analysis or Chaos Theory ?
What does this have to do with this topic ?


Cheers

[renormalised (Carl)]

Originally Posted by CraigS

Carl;

Who said anything about Bayesian Analysis or Chaos Theory ?
What does this have to do with this topic ?


Cheers

I mentioned them in passing, w.r.t. the topic. What does it have to do with the topic.....the topic's secondary point as was being spoken about was statistics, wasn't it.

Let's not devolve this topic into a pointless debate.

[CraigS]

Originally Posted by renormalised

Let's not devolve this topic into a pointless debate.

Overwhelmingly agreed !

Cheers

[CraigS]

Originally Posted by sjastro's signature

"Man is by nature a social animal; an individual who is unsocial naturally and not accidentally is either beneath our notice or more than human. Society is something that precedes the individual. Anyone who either cannot lead the common life or is so self-sufficient as not to need to, and therefore does not partake of society, is either a beast or a god. "
— Aristotle (Politics)

Cheers

[RB (Andrew)]

We're not discussing signatures here, we like to keep this section of the Astronomy forum (mostly) on topic.

[renormalised (Carl)]

= Politician debating science (or anything else for that matter!!)

= Journalist debating science

= General public debating science

= Scientist doing science

[RB (Andrew)]

Yes I konw Carl but Mike's ask that this section be strictly moderated.
Half the time I don't even know what you guys waffle on about, but I do see when it starts to turn into spam.

[renormalised (Carl)]

Originally Posted by RB

Yes I konw Carl but Mike's ask that this section be strictly moderated.
Half the time I don't even know what you guys waffle on about, but I do see when it starts to turn into spam.

That's not spam, by its definition. If we didn't have some humour in this section, the posts would become boring and rather tiresome. Or they would devolve into pointless debates with no direction. At least it breaks up the tedious air that sometimes appears here.

Plus, I only like waffle with maple syrup and icecream

[RB (Andrew)]

Yes I agree, a bit of humour is great in this section too.
No worries, just if we can keep it relevant to the topic of the thread and not stray too much.

[xelasnave]

Very interesting Steven, my favorite particle.
Craig I only recently found out about the rating but it was from some link of yours I followed. Thanks.

I visited Thunderbolts and had a good look ..over the last couple of days ( I have to rest and its overcast so no viewing)...but having been infected in the past with a similar morosophic approach to a pet subject myself my first emotion is embarrassement....however with a recognition I have moved on I must say they are determined that everything works because of their view on the U niverse.

I have no doubt they will see any discovery as support of their Universe...gives them an interest makes them feel good...no worries...other than a determination to destroy all other ideas before them
alex

[sjastro]

How theoretical physicists react to the sigma scale for experimental confirmation.

5 sigma:-
4 sigma:-
3 sigma:-
2 sigma:-
1 sigma:-

Hopefully this is not too off topic.

Regards

Steven

[CraigS]

Originally Posted by sjastro

How theoretical physicists react to the sigma scale for experimental confirmation.

What does the 'experiment' confirm, if the results fall into one of these bin categories ?

To me, it confirms the applicability of the Standard Model, as a means for explaining the behaviour of fundamental particles. This may also lead to further predictions/outcomes.

What about the results that don't fit into any of these bins ? What do have these mean about the physical phenomena, and what do these then say about the Standard Model ?

Cheers