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Stuart
2003-Jun-23, 02:28 PM
Some time ago, I read of some experiments in detecting solar neutrinos that were undertaken using a large tank of chemicals under a mountain. There was a comment that some future work may be done using the ocean deeps for this purpose.

What is going on in the solar neutrino area now? Have the experiments detected the particles and what's the consensus on neutrino science. And did we ever use sensors in the ocean deeps for this role?

Donnie B.
2003-Jun-23, 03:03 PM
Solar neutrinos have been observed for something like 30 years now, and indeed the results were somewhat unexpected.

The number of neutrinos detected was considerably lower than was predicted by theory. This led to the now-accepted idea that neutrinos are not massless, and can therefore decay from one type to another. The solar neutrinos do this (to some extent) on their way from the Sun to here, and the decay products are not detected by the older experiments (hence the shortfall). I think the latest generation of neutrino observatories can detect multiple flavors, and has confirmed this interpretation.

The neutrino experiments also observed a pulse of neutrinos from Supernova 1987a (hope I got the designation right). All the way from the Magellanic Clouds!

I don't know of any detectors in the ocean depths, but there's one experiment in a salt mine under Lake Erie.

Sunfish
2003-Jun-23, 03:26 PM
Check out today's APOD

(http://antwrp.gsfc.nasa.gov/apod/astropix.html)

ToSeek
2003-Jun-23, 04:08 PM
Check out today's APOD

(http://antwrp.gsfc.nasa.gov/apod/astropix.html)

Link that will still work tomorrow, etc. (http://antwrp.gsfc.nasa.gov/apod/ap030623.html)

The premier neutrino detection observatory is Kamiokande (http://www-sk.icrr.u-tokyo.ac.jp/about_kamioka.html), which is built inside a mine in Japan. They picked up a Nobel Prize a few years ago for detecting the varieties of neutrinos from the Sun and thereby demonstrating that they change enroute. More recently, they had a major accident that blew out most of their detectors. I'm not sure where they stand with regard to recovery.

tracer
2003-Jun-23, 07:29 PM
This led to the now-accepted idea that neutrinos are not massless, [ ... ]

The neutrino experiments also observed a pulse of neutrinos from Supernova 1987a (hope I got the designation right). All the way from the Magellanic Clouds!
I remember the discovery of the neutrino "hit" that coincided with the moment SN 1987A went off.

The thing that bugs me is, the neutrinos arrived at almost exactly the same moment as the light from SN 1987A started to reach us, which implies that the neutrinos were moving at the speed of light. However, if neutrinos are not massless, this means they have to be moving slower than the speed of light.

So ... what's going on here?

Rue
2003-Jun-23, 07:52 PM
There is one in Sudbury, Ontario (http://www.ewh.ieee.org/reg/7/millennium/neutrino/sno_blue.html)

ToSeek
2003-Jun-23, 08:03 PM
Actually, the neutrinos got here first! (http://zebu.uoregon.edu/~soper/StarDeath/sn1987a.html) But they have a head start because the neutrinos are generated in the interior of a supernova, while it takes some time for light to reach the surface. Still, neutrinos must travel at 99.9999% of the speed of light (add more 9s as needed).

Eta C
2003-Jun-23, 08:13 PM
Both experiements made significant discoveries. Super K found evidence for neutrino oscillation in neutrinos produced by cosmic rays hitting the atmosphere in 1998 (http://www.aip.org/enews/physnews/1998/split/pnu375-1.htm). These were muon neutrinos (there are three flavors: electron, mu, and tau neutrinos). SK saw a difference in the flux of mu neutrinos produced above it and those that had to pass through the earth to reach the detector. This was evidence that those passing through the earth changed flavor. An earlier version of this detector saw the neutrinos from SN1987A.

Sudbury did the work that resolved the solar neutrino problem. Their detector can observe all three flavors and found the total flux in agreement with that predicted by solar models. This was reported last April (http://www.aip.org/enews/physnews/2002/split/586-1.html). This work was related to the 2002 Nobel Prizes. (http://www.aip.org/enews/physnews/2002/split/608-1.html)