Why don't neutrinos interact much with matter?

[Evil Dr Ganymede]

Given it's so difficult to detect neutrinos, would anyone know if they're actually picking up neutrinos from the cosmic neutrino background? Would they have a particular signature (a certain energy?)? Would you be able to detect enough of them to make a 'neutrino map' of the sky?

[t00fri]

Given it's so difficult to detect neutrinos, would anyone know if they're actually picking up neutrinos from the cosmic neutrino background? Would they have a particular signature (a certain energy?)? Would you be able to detect enough of them to make a 'neutrino map' of the sky?

Here is a nicely written paper by a colleague and friend of mine about the exciting possibility to detect cosmic relic neutrinos via the so-called "Z-burst" scenario, I discussed above.

http://xxx.lanl.gov/pdf/hep-ph/0111112

(a PDF viewer in your browser is needed, e.g. Acroread...)

Reading the first page might suffice to get a good idea...

For this mechanism to work, it is crucial that

i) Neutrinos do have a nonvanishing (small) mass, for which there is convincing evidence from all recent neutrino oscillation experiments.

From WMAP we also know a cosmic upper limit

Code: Select all

Mass(neutrinos) <~ 0.2 eV


ii) Cosmic sources must exist that may produce a flux of extremely high-energetic neutrinos. These would then be able to interact with the cosmic relic neutrinos on the Z-boson resonance, which boosts the rate by many orders of magnitude! A direct signal for the Z-burst process would then be absorption dips at the known resonance energy

Code: Select all

E~4.2 *10^21 eV (1eV/mass[neutrino])


in the spectrum of ultra-high-energy cosmic rays detectable on earth! A few such extremely high-energetic cosmic ray events have been observed already. So things are within reach and most interesting...

Present and future neutrino detection facilities will be directly able to search for the required ultra high energy neutrino sources and/or cosmic ray events, respectively. Examples are the present (AMANDA) and future (ICECUBE) neutrino "telescopes" at the South pole or the forthcoming AUGER experiment in South America.

It is worth emphasizing that this example provides an excellent illustration why and how particle physics and cosmology are merging recently...

Bye Fridger

[Draconiator]

...I wonder how many neutrinos cruise through our bodies in any given minute...

[Evil Dr Ganymede]

...I wonder how many neutrinos cruise through our bodies in any given minute...

I thought I read somewhere that the neutrino flux was about 55 per cubic centimetre per second on Earth? Quite a lot, and chances are that only a handful of them would actually interact with our bodies in a human lifetime.

[t00fri]

...I wonder how many neutrinos cruise through our bodies in any given minute...

I thought I read somewhere that the neutrino flux was about 55 per cubic centimetre per second on Earth? Quite a lot, and chances are that only a handful of them would actually interact with our bodies in a human lifetime.

56/cm^3 is the number density just due to the relic neutrinos in analogy to the microwave photons (you may have read that number in my post above?;-)). But in addition, there is a significant flux of neutrinos penetrating our bodies from the SUN, of course...
The sun is a powerful nuclear reactor as everyone will be aware.

And more...

There is a strong neutrino flux from cosmic ray air showers due to weak decays of pi mesons etc.

Bye Fridger

[Harry]

...I wonder how many neutrinos cruise through our bodies in any given minute...

As found on a couple of webpages (google is your friend): the number of solar neutrinos going through a surface with 1 sq. cm surfaace is about 6*10^10 (60 000 000 000) per second. Makes a much more impressive number than the density

Harald

[t00fri]

Have a look at the two images below, illustrating some of the involvement of my laboratory (DESY) in hunting cosmic neutrinos via the "neutrino telescope" AMANDA located exactly at the South pole! The next step after AMANDA will be the international ICECUBE experiment at the same location, however with a dramatically enlarged neutrino detector volume under the ice.

The second image shows the beauty of the FIRST sunrise at the AMANDA station after a long winter of total darkness and isolation...

Anybody wants to go there for a month or two? "Nightlife" is said to be most exciting

Bye Fridger

[Evil Dr Ganymede]

Hey, you got some nifty halo/refraction effects around the sun in that second photo (unsurprisingly, since most of that is caused by ice in the high atmosphere)! is that two sundogs and part of a 22 degree halo I see on the horizon on either side of the sun?

[chris]

Have a look at the two images below, illustrating some of the involvement of my laboratory (DESY) in hunting cosmic neutrinos via the "neutrino telescope" AMANDA located exactly at the South pole! The next step after AMANDA will be the international ICECUBE experiment at the same location, however with a dramatically enlarged neutrino detector volume under the ice.

The second image shows the beauty of the FIRST sunrise at the AMANDA station after a long winter of total darkness and isolation...

Anybody wants to go there for a month or two? "Nightlife" is said to be most exciting

Beautiful pictures!

I'd jump at the chance to spend at the month at the South Pole station. Preferably in the summer, but then again, the aurora australis and clear dark skies of the winter would be wonderful as well.

--Chris

[granthutchison]

Hey, you got some nifty halo/refraction effects around the sun in that second photo (unsurprisingly, since most of that is caused by ice in the high atmosphere)! is that two sundogs and part of a 22 degree halo I see on the horizon on either side of the sun?

Looks like there might be a sun pillar, too, unless it's an odd lens flare.

Grant

[t00fri]

Hey, you got some nifty halo/refraction effects around the sun in that second photo (unsurprisingly, since most of that is caused by ice in the high atmosphere)! is that two sundogs and part of a 22 degree halo I see on the horizon on either side of the sun?

Well observed Dr. Evil!

I did not comment on these beautiful effects, curious to see who will spot them and has the right explanation ready;-). No wonder...

Bye Fridger

[Evil Dr Ganymede]

Well, Mr Freezer , I did spot similar effects in the sky here a few months ago...

[t00fri]

Well, Mr Freezer , I did spot similar effects in the sky here a few months ago...

Anybody recognizes what's going on (optically) on this beautiful photograph?



or here

or here

or here

or perhaps here


My bet is that the name of the effect will be revealed by at least one of our well known "Celestians", but not how it really works. The underlying theory was only fully derived as late as 1969.

Grant,

Mie theory could do it in principle, but those /hundreds/ of wildly oscillating terms necessary here in the Mie partial wave expansion do not allow much insight...

One reason why I never liked the Mie theory;-)

Bye Fridger

[granthutchison]

Anybody recognizes what's going on (optically) on this beautiful photograph?

It's a glory (the coloured halo of light), surrounding a Brocken Spectre (the observer's shadow).
The glory is produced in the same way as a corona (the coloured rings around the Moon when seen through thin cloud). The colours derive from constructive interference of light diffracted around water droplets - different wavelengths reinforce each other at different scattering angles. However, the light that forms a glory comes from the anti-solar point (as you can see by the fact that it surrounds the shadow of the photographer's head in each picture), so the light must be undergoing reflection to reach your eye. How it manages it be both reflected (usually a central phenomenon) and diffracted (usually an edge phenomenon) by the water droplets is something of a mystery, I think.

The underlying theory was only fully derived as late as 1969.

Nussenzveig?

Grant

PS: You'll often see glories if you travel by plane ... they surround the shadow of your plane on the clouds below. If you look carefully, you'll see that the glory always surrounds the exact position of your seat in the plane (as it must do, because it forms exactly opposite the position of the Sun). I once manage to get half the passengers on a small plane wandering up and down the aisle and peering out the windows, checking that the glory moved from the front to the back of the plane's shadow as they moved from a front to a rear seat!

[t00fri]

...
How it manages it be both reflected (usually a central phenomenon) and diffracted (usually an edge phenomenon) by the water droplets is something of a mystery, I think.

No surprise, Grant knows most about the Glory effect;-).

+++++++++++++++++++++++++++
Yet the hardest and most interesting part is missing...That's what was only understood in the late 60's!
+++++++++++++++++++++++++++

The question to answer is this:

How does the light get to the "anti-diffractive" direction, i.e. exactly to 180 degrees ?? Like in usual forward diffraction there is a caustic line connecting 0 degrees and 180 degrees, that naturally amplifies the light which manages to get there.


[The position of caustics can easily be identified within the familiar (?) WKB approach by calculating the geometrical locus where the flux factor in the /denominator/ vanishes.]

Why is it hard to scatter generic incoming light rays exactly to 180 degrees??

Well...
A generic incoming ray hitting the water droplet (composing the fog) splits in general into a component that is reflected on the droplet's surface and one that is refracted into the droplet according to Snell's law. Right?
The latter tells us how the involved angles all depend on the droplet's refractive index n.

Next, that ray in the droplet undergoes further reflections inside the droplet at its spherical wall, each time emitting part of the light again to the outside at an increasing scattering angle. Eventually these emitted rays from multiple internal reflections may well come close to 180 degrees. Yet unfortunately, this is not close enough for amplification by the 180 degree caustics;-), since for non-special refraction indices n, 180 degrees will never be reached exactly (need an illustration?). Only for very special values of n this could accidentally happen.

It was discovered only in 1969 by S. Nussenzveig that there is a classically forbidden, diffractive (surface) component, the so-called "surface creep waves"
that will bridge the (small) gap from the last internal reflection to exactly 180 degrees! That's the real "secret" of the Glory effect!! Diffraction again was the crucial missing piece...The most elegant part in Smuel Nussenzveig's 2 long papers in "Journal of Mathematical Physics" was to isolate this surface creep wave component by means of a so-called "Sommerfeld Watson" transformation of that horrible Mie sum;-)

PS: You'll often see glories if you travel by plane ... they surround the shadow of your plane on the clouds below. If you look carefully, you'll see that the glory always surrounds the exact position of your seat in the plane (as it must do, because it forms exactly opposite the position of the Sun). I once manage to get half the passengers on a small plane wandering up and down the aisle and peering out the windows, checking that the glory moved from the front to the back of the plane's shadow as they moved from a front to a rear seat!

Indeed seeing the Glory from planes on the clouds below is the easiest way to spot this interesting effect. The photographs above collect other possible and much rarer to meet occasions...

Bye Fridger

[granthutchison]

Yet the hardest and most interesting part is missing...That's what was only understood in the late 60's!

Interesting. I knew Nussenzveig had produced a complex bit of mathematical physics that allowed the reflected light to come straight back off the edges of the droplets, but had formed the impression that this was not entirely accepted by atmospheric physicists - hence my remark about "something of a mystery". Looking back through the books just now, I see where I got the idea ... Robert Greenler is rather lukewarm about Nussenzveig in Rainbows, Halos, and Glories, but it's difficult to tell whether he finds fault with the theory or just resents the complexity of it when compared to the simple optics that can be used adequately for other phenomena. Lynch and Livingston are more outspoken in Color and Light in Nature: "... a good physical explanation is, in our opinion, lacking."
<Shrug.> I don't understand nearly enough to take sides.

But I'm intrigued that you give Nussenzveig's first name as "Smuel" ... the initials are given as "H.M." in references from the 1970s. Is there a father-and-son operation going on?

Grant

[t00fri]

Yet the hardest and most interesting part is missing...That's what was only understood in the late 60's!

Interesting. I knew Nussenzveig had produced a complex bit of mathematical physics that allowed the reflected light to come straight back off the edges of the droplets, but had formed the impression that this was not entirely accepted by atmospheric physicists - hence my remark about "something of a mystery". Looking back through the books just now, I see where I got the idea ... Robert Greenler is rather lukewarm about Nussenzveig in Rainbows, Halos, and Glories, but it's difficult to tell whether he finds fault with the theory or just resents the complexity of it when compared to the simple optics that can be used adequately for other phenomena. Lynch and Livingston are more outspoken in Color and Light in Nature: "... a good physical explanation is, in our opinion, lacking."
<Shrug.> I don't understand nearly enough to take sides.

But I'm intrigued that you give Nussenzveig's first name as "Smuel" ... the initials are given as "H.M." in references from the 1970s. Is there a father-and-son operation going on?

Grant

Grant,

as to Nussenzveig's name you are right, of course. Yesterday night I had written these things only from my memory dating back 25-28 years!;-). At this early time my wife and I wrote a series of papers were we adapted these new ideas of "surface creep waves" in advanced optics and -- along with this -- a semiclassical formalism of tunnelling using complex classical paths in functional integrals, to diffraction scattering in elementary particle physics.

We actually speculated at the time that there may be an analog of the "Glory effect" also in particle physics!

I gave a large amount of talks about this novel idea and even was invited to give a respective plenary talk at an intl. conference in Osaka/Japan

Thirty years later these concepts are still "en vogue" but have been renamed in our field as "instanton" effects...

I knew Nussenzveig's teacher Prof. Guido Beck from Bariloche/Argentina quite well personally, while he was still alive. At Bariloche they did theoretical research to explain the subtleties of the rainbow and many related phenomena including the glory for many years. Nussenzveig I never met in person.

However, my wife and I studied his papers

[actually here is the correct reference:
H.M. Nussenzveig, Journal of Math. Phys. 10 (1969) 82; 10 (1969) 129; also Annals of Phys. 34 (1965) 23]

carefully over weeks, which was a quite difficult and tedious task. I simply claim that your book authors above might well have had neither the patience nor the math training to seriously judge for themselves the sound quality of Nussenzveig's results. We checked every single formula and convinced ourselves that his results were undebatably right.

As I stated repeatedly also in other posts, Mie theory becomes quite useless for kR>>1, with R being the droplet radius and k the wave number of the incident light. The main reason is that e.g. for the range 30 ...1000 of kR, where the glory is typically observed, a huge number of oscillatory terms contributes.

Nussenzveig's main merit was to rigorously derive a new asymptotic expansion for the exact Mie theory for kR >>1. The trick was to apply the so-called Sommerfeld Watson transformation to the Mie series. The rest is partly tedious math but it is free of any further assumptions. The merit is that the new expansions are highly accurate for any n, allow a full discussion of subtle color phenomena and exhibit a reformulation of general diffraction effects in form of the already mentioned "surface crep waves".

Nussenzveig also refers to sophisticated laboratory experiments using laser light, where his predictions were ingeniously verified. A single droplet of different refraction index was cleverly suspended and irradiated with monochromatic laser light. The shrinking radius of the droplet was monitored while evaporation took place! This way the n-dependence, color, R and k dependence of his theory could be tested in great detail and accuracy...

I only found scanned versions from the Japanese KEK laboratory of our old papers on the net. So, for your information and amusement, let me quote the URL of the shortest one,
published in Physics Letters B70 (1977) 88:
http://ccdb3fs.kek.jp/cgi-bin/img/allpdf?197701082
[use Acroread to view the PDF format]

Have a look in the introduction and the references... An amusing piece of "history"....

The beauty of Nussenzveig's results is that the surface creep waves may be translated back into a very topical functional integral language of field theory by complexifying the time! This way one arrives at a semi-/classical/ description of classically forbidden diffraction phenomena in terms of "bending rays propagating along geodesics" of the scatterer's surface!
Whatever that surface may be!

In addition, this formalism can be readily transcribed into curved spaces (viz. general relativity...)

In modern times we analogously go over from Minkowsky space to Euclidean space, which effectively amounts to the continuation from real to imaginary time.


Finally, yesterday night, being very tired after a long working day, I had apparently mixed up Nussinov's first name (Smuel) with Nussenzveig's

Bye Fridger

[granthutchison]

as to Nussenzveig's name you are right, of course. Yesterday night I had written these things only from my memory dating back 25-28 years!

The reason I even remember his second name over the same time span is simply because I stole it for a character in a short story. (The nerdy protagonist's name, "Lester Nussenzveig", was unfortunately the part of the story that worked best.) The initials I only encountered when I did a quick web search on "Nussenzveig" and "glory" to check the time-frame matched what you were talking about.

I simply claim that your book authors above might well have had neither the patience nor the math training to seriously judge for themselves the sound quality of Nussenzveig's results.

That's certainly compatible with what I'm reading ... I was getting a sense of disgruntlement from Greenler about the complexity of the maths required to predict the sizes of the coloured rings.

Have a look in the introduction and the references... An amusing piece of "history"....

Ah, typing up papers on a manual typewriter with carbon paper. How much fun was that?
I think I don't understand enough to get the full amusing historical effect, though it occurs to me I haven't heard the phrase "bag confinement model" for a long time ...

Grant

[Evil Dr Ganymede]

I was going to say "that's what you see around a shadow of a plane", because I've noticed that on a couple of occasions (never realised exactly what it was, but I figured it was an optical effect of some sort), but then you showed the photo that was clearly taken by a person on the ground. I didn't know it had a specific name though

[granthutchison]

I was going to say "that's what you see around a shadow of a plane", because I've noticed that on a couple of occasions (never realised exactly what it was, but I figured it was an optical effect of some sort), but then you showed the photo that was clearly taken by a person on the ground. I didn't know it had a specific name though :)

There's another lighting effect that crops up around the antisolar point, which you often see around an aeroplane shadow when flying low over grass or cropland. On foot, you can see it at sunrise when there's dew on the grass:

It's very evident once you have it pointed out to you, but remarkably few people seem to notice it spontaneously.
It's called heiligenschein, and I wrote a bit about it for a Scottish newspaper a few years ago: it comes in two varieties, wet heiligenschein (the brighter kind you usually see in dew-covered grass) and dry heiligenschein (which is the kind you usually see from aircraft). Dry heiligenschein also seems to be a feature of lunar dust, at least on the maria explored by Apollo ... several astronauts reported that the shadow of their helmets on the dust was always surrounded by a bright nimbus.
I spoke to a bush pilot after the Zambian total solar eclipse a few years ago, and he said that he was in flight during the onset of the partial phase. He could see the patch of heiligenschein around his plane gradually turning crescent-shaped below him!

Grant