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2007-07-28 17:56:21
Neutrinos -

If u gonna shoot em thru earth interior i.e thru crust , mantle etc...

In form of a beam... it means dat these neutrinos hav properties of waves...

and can be collected as Sound waves in a SONAR.... juz an example

If this is possible... u can calculate its size and weight
2007-07-28 17:57:29
fyi relaying from as there are 80,000 members of that community hope it creates soem interest there
Stephen Brooks
2007-07-29 12:18:16
Sound waves are vibrations of atoms (the atomic nuclei and surrounding electrons) that move through a material.  Most neutrinos don't scatter off any of the atoms they pass through in the Earth, so they won't exchange any momentum with them.  There will be a very small sonic wave created when the occasional one causes a nuclear recoil, but this will be drowned out by vibrations from heat and other radioactive decays in the Earth's interior.

However, there is a "matter effect" where neutrinos are predicted to be refracted (very slightly) by layers in the Earth.  (The first paper I found on it is here, basically says how the electron density in the Earth modifies the precession of e-type neutrinos).  This is sometimes mentioned in meetings as something the neutrino factory could also measure, though it is generally believed to be more difficult to detect (smaller) than the mass splittings themselves - in fact, the matter density effect gets in the way of doing accurate measurements of other things because it relies on estimates of the density of the Earth's layers!  You measure (oscillations + matter effect) in the case of electron neutrinos.  Fortunately the neutrino factory produces muon neutrinos as well, which are unaffected, so there is the possibility of getting some calibration on that.

This is part of "neutrino phenomenology", which I'm not an expert in - I do the accelerator parts.  I'll have to ask someone what the current estimate of the size of the matter effect is.
Stephen Brooks
2007-07-29 12:26:51
Actually in that paper they take the standard 6 parameters of neutrino oscillations and relate them (page 9) to a set of 5+1 where the 5 are independent of matter and the 1 is proportional to the amount of matter.  So the neutrino factory will measure some of those six (or a combination), but only for one will the geologically estimated density of the path in the Earth have to be inserted.
Barrie Tite
2007-08-25 12:17:42
So am I right in thinking that this project is all about characterizing the properties of neutrinos, and there is no prospect of using it to infer anything about the internal structure of the Earth?
Stephen Brooks
2007-08-25 15:31:11
Yes, it'd doubtful we'll be able to work out a lot about the Earth from this experiment - seismic waves are more accurate for that currently anyway.
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