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Re: neutrino mass



Ludwick,
There is actually a difference in the number of solar neutrinos
observed at night time from day time due to the extra distance they have
to travel through the earth. This extra distance may give the neutrino
the extra time it needs to oscillate. I think I remember something about
this in a paper that can be found in Physics Review Letters or as a
preprint from http://xxx.lanl.gov.
As for resolution, I think they do a great job as is given the
sheer volume of the tank and relatively large size of the PMT's they use.
You will probably have to wait until the next generation neutrino
experiments, like KAMLAND or ORLAND, to see better resolution and more
statistics since they accept neutrinos from many more neutrino
producing processes.
This discovery of mass for the neutrino is nice for the Standard
Model, even though it says that the nu mass should be zero. Why? Because
then the different generations of leptons have a mixing angle between them
just like for the quarks. So now we have equivalents to quarks changing
flavor. I will be interested in what Super K says this angle is along
with their delta mass squared and then see what future experiments can do
to confirm this result. Nice for physics beyond the Standard Model.



Sam Held


On Fri, 5 Jun 1998, LUDWIK KOWALSKI wrote:

According to the front page article in The New York Times the essence
of the neutrino experiment is in the comparison of what comes from
above with what comes from below (after traveling through Earth). The
orientation of light cones, from the Cerenkov effect, helps to
distinguish one direction from another.

They say that the mass of the neutrino can be as large as several eV.
This helps to answer the question about measuring it directly. Even if
the mass of a neutrino were 100 eV, measuring it directly would be
impossible. The accuracy of atomic mass measurements, as far as my table
shows, is not better than several hundreds of eV. But who knows, given
enough motivation mass spectrometrist may be able to generate more
accurate data.
Ludwik Kowalski