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Karl
2001-Oct-23, 12:13 PM
[i]"The consensus is now that less boron 8 is produced from the sun, which in turn reduces the number of solar neutrinos by around 20 percent compared to previous calculations," Gagliardi says.[i]

http://www.sciencedaily.com/releases/2001/10/011022030224.htm

Russ
2001-Oct-23, 12:31 PM
So does this have anything to do with neutrinos changing flavor as they travel between the Sun and Earth? The last I read in Scientific American, the reason the count was low is because they changed flavor in flight.

So I guess my question is Which is correct Boron 8 absorbtion or flavor change,...or both?

Karl
2001-Oct-23, 12:37 PM
On 2001-10-23 08:31, Russ wrote:
So does this have anything to do with neutrinos changing flavor as they travel between the Sun and Earth? The last I read in Scientific American, the reason the count was low is because they changed flavor in flight.

So I guess my question is Which is correct Boron 8 absorbtion or flavor change,...or both?


As I understand it, both. I don't think the flavor-changing completely explained the shortfall, but the combination comes much closer.

ljbrs
2001-Oct-24, 11:58 PM
I believe, from my more recent readings in *Nature* and in *Science* (and on .edu and .gov websites) that flavor change (due to neutrino oscillation) is the presently-accepted reason for the shortfall in the neutrino count from the Sun.

ljbrs

Hale_Bopp
2001-Oct-25, 03:23 PM
There is a new experiment being constructe at Fermilab called NUMI which will study flavor changing of neutrinos. A neutrino beam will be measured at Fermilab and then again at a detector in Minnesota. The distance should allow them to detect flavor changing.

Rob

frenchy
2001-Oct-25, 09:25 PM
A few different nuclear reactions produce neutrinos in the Sun and the neutrinos from each reaction has a different energy spectrum. Different experiments measure different mix of those neutrinos the two 'best' (SNO and Super kamiokande) measure only the flux from the Boron 8 neutrinos, while other measure PP and Berrylum 7 neutrinos (you also have a few neutrinos from the CNO cycle and the so-called hep neutrinos).

All that to say that Be7 and B8 neutrinos fluxes can be played around substantially by changing the physics of the core only slightly, within the constraints from helioseismology. The killer is the PP neutrinos which are closely correlated to the solar luminosity. To change those you need to play with the solar structure quite a bit which does not seem probable at this point.

To account for all the experiments one needs to invoke the neutrino oscillation models. But that does not mean that the source of the neutrinos (i.e. the solar core) is terribly well known. As oscillation models have a bit of of a hard time to match with the experiments it shows that not everything is perfectly understood yet.

Or something like that... /phpBB/images/smiles/icon_smile.gif

ljbrs
2001-Oct-28, 12:01 AM
That's science for you. Uncertainty rules. For those who wish for certainties, one should stay well away from anything scientific. Of course, anything unscientific would be wrong, so you might have wrong *certainties* instead of right *uncertainties*.

Now, I am not certain about all of this, so there!

ljbrs /phpBB/images/smiles/icon_smile.gif

jkmccrann
2007-Oct-02, 03:19 PM
Please note, this is a somewhat older thread I've come across.

With relation to this question - but slightly different, have we been able to measure the neutrino flow from any extra-solar star systems? To use for comparative purposes? Or indeed are there any plans to launch instruments perhaps into Earth orbit to achieve this?

Kaptain K
2007-Oct-02, 03:35 PM
Please note, this is a somewhat older thread I've come across.

With relation to this question - but slightly different, have we been able to measure the neutrino flow from any extra-solar star systems? To use for comparative purposes? Or indeed are there any plans to launch instruments perhaps into Earth orbit to achieve this?
You're joking, right? Neutrinos (from any source) are extremely hard to detect, much less determine a source.
AFAIK, the only extra-solar source of neutrinos that has been detected is SN 1987A and that was by the time of arrival rather than by direction.

StupendousMan
2007-Oct-02, 03:37 PM
Please note, this is a somewhat older thread I've come across.

With relation to this question - but slightly different, have we been able to measure the neutrino flow from any extra-solar star systems? To use for comparative purposes? Or indeed are there any plans to launch instruments perhaps into Earth orbit to achieve this?

Several detectors on Earth measured a few neutrinos from the explosion of SN 1987A in the Large Magellanic Cloud.

The only sources which would produce measurable neutrino fluxes are (to my knowledge) core-collapse supernovae in the Milky Way or one of its satellites. Ordinary stars produce far too few neutrinos for us to detect here on Earth (or in space near Earth).

trinitree88
2007-Oct-02, 04:25 PM
You're joking, right? Neutrinos (from any source) are extremely hard to detect, much less determine a source.
AFAIK, the only extra-solar source of neutrinos that has been detected is SN 1987A and that was by the time of arrival rather than by direction.

Kaptain. K. The detection of neutrinos from SN1987a at Kamiokande, and the IMB was via Cherenkov cones from neutrinos striking water molecules. Several cones from the prompt burst all radiate their axes towards a general direction in the sky....the Large Magellanic Cloud...hence confirming not only the timing of the prompt burst, but their most likely point of origin...SN1987a. pete

see;http://www-personal.umich.edu/~jcv/imb/imbp4.html

Fortunate
2007-Oct-02, 07:24 PM
Please note, this is a somewhat older thread I've come across.

With relation to this question - but slightly different, have we been able to measure the neutrino flow from any extra-solar star systems? To use for comparative purposes? Or indeed are there any plans to launch instruments perhaps into Earth orbit to achieve this?

I believe that fusion in the cores of stars produces relatively low energy neutrinos (high KEV and low MEV scale). I don't think Super K receives a high enough flux of these to locate any point sources other than the sun and nearby supernovae (only example so far is SN1987A). Another detector, Borexino, just came online this summer to detect Be7 neutrinos, the flux of which is about 100 times (I think) that of the B8 neutrinos detected by Super K. Much bigger water Cerenkov projects such as UNO and HyperK are in the planning stages as is a proposal named GADZOOKS!, which might greatly increase the sensitivity of water Cerenkov detectors. IceCube, a square kilometer detector currently under construction at the South Pole, will not be sensitive to KEV and MEV neutrinos but will be optimized for TEV and PEV sources (maybe gamma ray bursts, AGN, who knows what?).

Tim Thompson
2007-Oct-02, 08:05 PM
"The consensus is now that less boron 8 is produced from the sun, which in turn reduces the number of solar neutrinos by around 20 percent compared to previous calculations," Gagliardi says.
http://www.sciencedaily.com/releases/2001/10/011022030224.htm

Note that the date on the page is 2001, so the results are hardly "new". The paper has garnered only 1 citation thus far, and so is probably not as directly important to the solar neutrino question as one might think. And, in any case, not far after the quote give by Karl above, we find ...

"A big ambiguity has been resolved," Gagliardi says. "This new result sets our calculations of stellar physics on a much firmer foundation, which makes the interpretation of the results in terms of neutrino oscillations considerably more reliable than it was before."
It certainly appears that these old results are already incorporated in the neutrino oscillation framework.

trinitree88
2007-Oct-03, 08:41 PM
A new ArXiv preprint by D.L.Khoklov suggests that entanglement of neutrino and electron eigenstates is causing missing neutrinos in several experiments, with numerical predictions bearing him out pretty well. Interesting. Pete
see:http://arxiv.org/PS_cache/physics/pdf/0703/0703200v4.pdf