How do neutrinos do it?

[Qfwfq]

AFAIK, neutrinos are circularly, or “not” polarized.

Circularly doesn't mean not polarized. It only makes sense to say unpolarized in the sense of not knowing the polarization state.

 

Thouh some experiments involving lenses, diffraction grates and similar techniques (like all particles, neutrinos have a wave nature, so, even though they only weakly interact with ordinary matter, can be manipulated optically) have examined neutrino polarization, I don’t think any of the major detectors have, or would gain any advantage by doing so.

Do you have a reliable source? They would have to have lenses and diffraction grates that the neutrino interacted with. As far as I can see, optical manipulation would require sufficient soft interaction via virtual weak bosons and I'm not sure if it's feasible. The way to know anything about the polarization states would be, rather, by the outcome of the observed events.

[CraigD]

Thouh some experiments involving lenses, diffraction grates and similar techniques (like all particles, neutrinos have a wave nature, so, even though they only weakly interact with ordinary matter, can be manipulated optically) have examined neutrino polarization, I don’t think any of the major detectors have, or would gain any advantage by doing so.

Do you have a reliable source?

Not any really good ones. I made the claim based on a quick google search of “neutrino polarity” and “neutrino optics”, which yielded finds such as Very Long Baseline Experiment and The Reference Frame: Michele Papucci: neutrino optics, and, frankly, recollection of a few hard science fiction stories describing future development in optics that allow neutrinos to be used as a sort of “super x-ray radar”, augmented by personal speculation based on basic physics. Upon further checking, I’m not sure if anyone has achieved or even proposed any way to lens neutrinos with anything other than gravity (with which they interact as strongly as any fermion).

 

I’ve made a sloppy, possibly deceptive claim, and humbly beg pardon. :lol:

As far as I can see, optical manipulation would require sufficient soft interaction via virtual weak bosons and I'm not sure if it's feasible. The way to know anything about the polarization states would be, rather, by the outcome of the observed events.

As Qfwfq notes, getting enough neutrinos to exchange W or Z bosons with another fermion seems to be major difficulty in optically manipulating neutrinos. I’m neither sure it’s feasible, nor unfeasible. I suspect than any such optics would be very “lossy”, rather like one sees in a reflector telescope with a finished but unsilvered glass mirror, moreso by a large factor, and require many advanced techniques to “enhance” into useful images.

 

If such a technology could be made to work, though, it could be spectacular, providing direct images of the interior of stars with nearly no interference from intervening dust, gases, or even massive solid objects. With enough processing, neutrinos have the potential to provide data about matter with which they’ve weakly interacted, unhindered by other intervening matter. Direct images of the interior of planets, images of objects on the other sides of planets, etc., all seem withing the real of possibility. :lol:

[jungjedi]

maybe you could use some beig TOCOMAC to lense the nuetrinos if you fired it up with dueturium because of the weak interaction with the dueturium nuclia the electron antinutrino might be lensed in a very,very very...very very strong electric bottle of a tocomac.

A Search for Solar Electron Antineutrinos at the Sudbury Neutrino Observatory

[Qfwfq]

I’ve made a sloppy, possibly deceptive claim, and humbly beg pardon.

Don't worry Craig, and don't be overly :rolleyes:.

 

I suspect than any such optics would be very “lossy”, rather like one sees in a reflector telescope with a finished but unsilvered glass mirror...

Regarding a diffraction grating, yes, but for a lens I'd say it's more like having a mirror with a perfect surface, albeit very, very, all too toooooo flat! Alternatively, like using a lense of a glass that's highly transparent but has almost the same refractive index as the vacuum. No doubt Earth acts as a lens for the buggers, but I wonder how many parsecs its focal length must be...

 

...with nearly no interference from intervening dust, gases, or even massive solid objects. With enough processing, neutrinos have the potential to provide data about matter with which they’ve weakly interacted, unhindered by other intervening matter.

Which is the very reason for the difficulty.

 

maybe you could use some beig TOCOMAC to lense the nuetrinos if...

Are you sure you don't mean a TOKAMAK? Or, if you prefer, a Токамак which means "тороидальная камера в магнитных катушках".

[ronthepon]

Er, by the way...

 

Neutrinos ARE effected by gravity in pretty much the same was photons. The thing that makes neutrinos different is that they don't interact at all with photons, and so other then a direct collision there is no way for any other fermion to mess with them.

Um- what is the force that plays during the 'direct collision'? Do neutrinos feel the strong nuclear force as well? Or is it something else?

[CraigD]

Um- what is the force that plays during the 'direct collision'? Do neutrinos feel the strong nuclear force as well? Or is it something else?

Only the weak force – the W+, W- and Z “intermediate vector” or “weak force” bosons.

 

Because they have very short lives (about 3 * 10^-25 s), which limits their range of interaction to about 10^-18 m (about the classical diameter of an electron). So the probability of a neutrino interacting with a particle in a particular volume of space is only as great as the probability of fermion (an electron, a quark in a nucleon, etc) existing in the same volume, extended by 10^-18 meters. That’s about as close to a classical “direct hit” as is to be found in particle physics!

[Erasmus00]

Er, by the way...

 

Um- what is the force that plays during the 'direct collision'? Do neutrinos feel the strong nuclear force as well? Or is it something else?

 

The weak interaction. If the neutrino comes very close to a quark, they can interact through a weak interaction.

-Will

[CraigD]

If the neutrino comes very close to a quark, they can interact through a weak interaction.

Neutrinos can also interact with electrons via the weak (but not the strong) interaction. As I understand it, many neutrino detectors detect them due to their interaction with electrons.

 

Neutrinos are fermions, so obey the Pauli exclusion principle. This means neutrinos interact with other neutrinos, via the weak interaction. So, unlike light beams consisting of photon bosons, 2 beams of neutrinos can interact, similarly, but more weakly, than, for example, 2 beams of electrons.

 

I’m unsure of the practical implications of this. The more I consider neutrinos, the more questions I have about them.

[jungjedi]

Neutrinos can also interact with electrons via the weak (but not the strong) interaction. As I understand it, many neutrino detectors detect them due to their interaction with electrons.

 

Neutrinos are fermions, so obey the Pauli exclusion principle. This means neutrinos interact with other neutrinos, via the weak interaction. So, unlike light beams consisting of photon bosons, 2 beams of neutrinos can interact, similarly, but more weakly, than, for example, 2 beams of electrons.

 

I’m unsure of the practical implications of this. The more I consider neutrinos, the more questions I have about them.

 

are nuetrinos more given to react with other nuetrinos than they are other leptons like electrons

[CraigD]

are nuetrinos more given to react with other nuetrinos than they are other leptons like electrons

The answer is, I believe, between “no” and “it depends on the neutrino”.

 

AFAIK, the maximum interaction distance for the weak force is the same whether it is “carrying force” between an electron and a neutrino or a neutrino and a neutrino, so likelihood of an interaction should be about the same. The 3 neutrinos have very different masses, though (.0000043, .33, and 30 electon-masses), so the velocity change of most, but not all, neutrinos in neutrino-neutrino interactions should be greater than that of an electron.

 

Unlike an electron, however, detecting the speed and direction of an neutrino is very difficult, so measuring such effects may very difficult.

[Qfwfq]

Um- what is the force that plays during the 'direct collision'?

Actually, I find the term misleading, it hardly makes sense to talk about a "direct collision" between single quarks and leptons as we don't know of these having any radius at all, all tests of the highest possible spatial resolution so far show electrons as pointlike. The standard model seems convincing enough to consider them all non composite and pointlike.

 

Hadrons do have a spatial extent, they are a ball-like distribution of mainly quarks, antiquarks and gluons. The radius of a single nucleon is around 1 fm, or [math]\norm10^{-15}[/math] m. It therefore makes sense to talk about traversing a hadron, but this can even occur with little or no mishap. At collision energies of, for instance, 10 GeV or so, two protons can go right through each other and they don't always tear each other apart!

 

Do neutrinos feel the strong nuclear force as well?

Not at all, or they wouldn't be going through Earth so easily. As far as gravity goes, being just about massless they are practically the same thing as photons: They will simply follow a null geodesic (or almost).

 

Neutrinos are fermions, so obey the Pauli exclusion principle. This means neutrinos interact with other neutrinos, via the weak interaction. So, unlike light beams consisting of photon bosons, 2 beams of neutrinos can interact, similarly, but more weakly, than, for example, 2 beams of electrons.

Fermi or Bose statistics of the two incoming particles aren't so relevant in collisions because, even if they are of the same species, they could hardly be in the same state.

[Erasmus00]

Actually, I find the term misleading, it hardly makes sense to talk about a "direct collision" between single quarks and leptons as we don't know of these having any radius at all, all tests of the highest possible spatial resolution so far show electrons as pointlike. The standard model seems convincing enough to consider them all non composite and pointlike.

 

I apologize that I used sloppy language.

 

Anyway, as to the standard model implying pointlike particles, I strongly disagree. The standard model is plagued with infinities that can only be dealt with through renormalization, which is a process that (in a very loose sense) moves the infinity to where it "belongs." In all cases, these infinities are pushed into very high energy (short length scale) areas of the theory (more technically, often the "bare" lagrangian parameters are infinite).

 

Since the theory is blowing up at short length scales I think we can be fairly certain in saying that we don't at all know what is happening, and a more detailed interaction should probably be put in to help regulate these divergences. Consider condensed matter field theories, where often the physical spacing of some crystal lattice provides a limit that naturally removes infinities.

 

So, I think we can safely say we don't know whats happening at these short length scales where a "radius" of a fundamental particle might be coming into play. We also don't really have any experiments yet that can directly probe this area. Currently, string theory is in vogue, which puts in a specific short range structure to fundamental particles (i.e. it says that they are strings). Whether or not it is right, I believe one things is certain: the infinities of the standard model probably indicate we are NOT dealing with points.

-Will

[Qfwfq]

Certainly we don't know much about below the Planck scale, perhaps I was sloppy myself if I didn't explicitly say that I meant nothing about such scales. It is of course somewhat beyond the scope of this thread.