Thursday, January 26, 2006 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

AMANDA, neutrinos, and new physics

David Goss has pointed out a press release about

A system of neutrino detectors immersed deeply in Antarctic ice is measuring a single number, namely the ratio of up-going and down-going neutrinos, which nevertheless imposes constraints on new physics because various processes - such as colissions of very high-energy (typical example: around 20,000 TeV) cosmic neutrinos with the atoms of the atmosphere that may create microscopic black holes - contribute to this ratio. The ratio is more interesting than the overall number: the overall number depends mostly on astrophysical phenomena while the ratio mostly depends on particle physics that occurs in the Earth or in its vicinity. A better experiment of this kind, IceCube, is under construction.

For a flavor of this kind of physics and constraints, see

and an article in the new issue of Physical Review Letters. The homepages of the projects are here:

A more general topic: David Gross who was described as a new skeptic and sourball by a misinformation and brainwashing blog called "Not Even Wrong" - a blog addressed to those who can't distinguish s*it from gold - has calculated, during his lecture in India, that physics will be even more exciting in the 21st century and the string theory revolution is yet to come:

Gross who claims that he has been waiting for his Nobel prize only since 1994 argues that the following revolution will be even more shocking than the previous two.

All theater fans should see the new Hamlet of the 21st century, namely

I would like to remind the omnipresent intellectual trash that this article is about the neutrino detectors, new physics, the waves of physics discoveries, and a theater play from 2002. If you're unable to contribute anything about these topics, you are encouraged to submit your production to "Not Even Wrong" where the s*it will be undoubtedly rated as gold. On this blog, unfortunately for you, s*it is just s*it and we follow basic rules of hygiene.

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snail feedback (8) :


reader Belette said...

Hi Lubos. Todays test question is: what is 2 times 280. Is it (a) 380 (b) something a bit bigger?


reader Lumo said...

Dear Belette,

I suppose that you think that your deep question is related to neutrino detectors.

Your humble correspondent is always ready to help the world's climate research, so without hesitation, I will answer that it is 560, and I hope that it will help you and your equally talented colleagues in your research tremendously.

Incidentally, if you were interested, the number that you're interested in has oscillated with 100,000-year-long quasiperiods between 180 and 280, and its current value is close to the double of the average and more than the double of the minimum.

Even if you did not care about the minima and only considered the natural maximum, almost 50% has been added to the natural value already. If you find it that important, you may increase the estimates by a factor of two, but at any rate, the qualitative conclusions will be unchanged.

What we've added is exactly equal to the difference between the natural maxima and minima.

Enjoy your milk, and greetings to your father.

Best
Lubos


reader Quantoken said...

Sounds an interesting experiment. But what does it has to do with string theory? You have not shown us you can predict exactly how many down-going or up-going high energy neutrinos you can expect to detect, based on string theory calculation. String theory can't say anything about interaction cross-sections or reaction rates so it's out of the equation.

I am highly skeptical that they can obtain significant event counts to produce statistically meaningful result. If you read the 4 page paper carefully, you find that the author is trying desperately to STRETCH THE NUMBER to un-reasonable limit, in order to produce a reasonably looking event count.

According to the author, during a total of 15 years of experiment run (a very long time, isn't it?), he expects to detect mere 4 down going neutrino events and 20 up going events. Very small number and hardly enough to do any statistics, you would agree.

But even that (4,20) event count estimate is way too much optimistic. If you carefully exam his calculation, you find he stretched the numbers too much. A more realistic estimate would give you an event count 100 times lower. Rendering the experiment meaningless since your expectation of event count is less than ONE.

First big mistake the author made, is he used the effective aperture of individual detectors times the length of detector strings to estimate the number of target nucleons, thus attrived at NT = 6x10^38. That estimate is wrong because there is redundancy between detectors.

A more common sense estimate is actually calculate how many atoms are involves in the detection. This brochure says the total volume of ice in the IceCube is ONE CUBIC KILOMETER. One should be able to calculate how many nucleons is contained in one cubic kilometer of ice.

The density of ice is about 900 kilogram per cubic meter. So one cubic ice is 9x10^11 kilogram. The water molecule contains 3 nucleons, and has an atomic weight of 18. That means each 0.018 kilogram contains 3 times the Avogardro constant, 6x10^23 nucleons. Put those number together. The total number of target nucleons is 9x10^37.

The author used 6x10^38 nucleons, which is an over estimate of 7 times already.

The author also grossly over estimated the detection efficiency to be between 50% to 100%. No such efficiency exists. Think about it, one single muon is created a few hundred meters away, it does emit some number of photons, but for the photons to be almost 100% detectable by a detector a few hundred meters away, that is really a stretch. It takes many many many photos to trigger an event. During dark nights there are still billions of bilions of photons entering our eyes per second but we hardly see anything. I do not know how to calculate the quantum efficiency but it must be way below 100%.

Now the technical difficulties how you can run such an experiment for 15 years in the frigid cold in the southern pole? These detectors and instruments must run on continuous electricity. How do you supply stable electricity for 15 years? Using solar panels? Well half of the year on the southern pole will be permanent darkness without sun shine. So no solar energy.

You may think of batteries. But the temperature is so cold that the fluid of the batteries will freeze into solid, disabling the battery. If you read recent news about the cold snip in Russian, you know many people had to take their car batteries into their home to keep it warm over night and put it back on the car the next morning. Any one not bringing their battery home will not have a working car the next day. So battery option is out for the souther pole experiment due to the temperature.

Or some device burning gasoline to generate electric power? That would be subject to supply issues and human maintenence. And it is impossible to maintain it year around.

Anyway you look at it, the experiment simply can not be run continuously year around. You may be able to run some months during each year, but not all the time.

The author used a full 15 years to estimate the event count. Again that is a gross over estimate. The realistic number should probably be divided by 3 or 4.

After you factor in all these realistic consideration, I am sure the experiment simply will not produce enough event count to draw any statistically meaningful result of any kind.

Quantoken


reader Lumo said...

Dear Quantoken,

string theory is the current framework to parameterize the conceptual phenomena that actually occur at very high energy scales - which is why the press release is full of the term "string theory".

If the braneworld scenarios of string theory are correct, very unusual phenomena are plausible. For example, mini black holes and excited strings can be generated, and all of these effects would strongly influence the observed rates of the neutrinos.

As you can see, I described the experiment without direct links to string theory because the result will have impact not only on those who use string theory to study very high energy physics, but to everyone who studies it.

Best wishes
Lubos


reader Quantoken said...

Lubos said:

"and all of these effects would strongly influence the observed rates of the neutrinos."

But exactly how? Does it make the observed rate increase or decrease? And increase or decrease by how much percentage? You are unable to say anything definitely and quantitatively. You could only make ambiguious statement like the above without any quantification.

I am sorry, but if you are unable to say anything specific about an experiment, then the experiment can not be used to falsify or verify your theory. And so anything observed could well be attributed to something completely different, making your theory totally irrelevant. That's what I mean you are out of the equation.

For example, just an assumption, if the LQG group predicts that the event rate is increase by such and such percentage, and it matches the experimental value, and you string theory camp can't come up with a specific number. That will put you out of business.

But a much more likely outcome, like I said, is that due to the technical difficulty, the experiment simply will NOT produce enough event count to be statistically meanful for any result.

I wish you can jump in and do some quantitative estimates of the event rates. But I know your basic physics training is too poor to allow you to do any technical calculation.

Quantoken


reader Lumo said...

We know exactly how to calculate these rates of up/down high energy neutrinos for various models in string theory, and if you click at the hep-ph paper as those of the fellow readers who are not illiterate, you could even learn what these numbers are. I am not going to copy the articles here because this blog is not addressed to idiots who think that the world is incalculable and who are not able to open web pages with preprints.


reader Quantoken said...

Lubos said:

"....if you click at the hep-ph paper as those of the fellow readers who are not illiterate, you could even learn what these numbers are."

Lubos, are you trying to give more evidence that YOU are the illiterate one? I already opened the hep-ph paper. Printed it out. Read it. Verified all the numerical calculation. And discussed the numerical result the author provided, right above in my comment. You are too illiterate to see that I was discussing the numbers quoted from the paper.

But no, that is an phenomenology paper, not a theoretical paper. All the calculations of cross-sections the author did, is based purely on Standard Model. His event number, (4,20), is based on SM. If the experimental result show a deviation from that figure, it is a deviation from SM. And he showed how such deviation can be identified statistically. As for how such deviation should look like or how it can be calculated based on different theoretical model, the author said not a single word. He does NOT say anything how string theory predicts the cross-secion. He used cross section numbers calculated from Standard Model!

Too bad you are too illiterate to be able to read the paper and follow its calculation and discussion. You don't even know what the paper is talking about. It's only 4 pages and you can't read it, God grief!

Quantoken


reader Lumo said...

Dear Quantoken,

when I say that people are expected to be able to read, it also includes the ability to read the references and other papers.

The phenomenology of particular low-energy-gravity models is calculated at various places, e.g.


http://arxiv.org/abs/hep-ph/0107057


Predictions from TeV-scale excited strings:

http://arxiv.org/abs/hep-ph/0204112

Predictions from mini black holes:

http://arxiv.org/abs/hep-ph/0202081

If you expect me that I will be telling you how to read every letter, you will be disappointed. This was the last stupid question I answered for you.

I encourage you to try to triple your IQ so that you will be able to answer your next trivial questions without the help of others.

Best
LM