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Re: neutrino mass



I have a question about a finite mass neutrino. If it is so, then it takes
over
as the smallest non-zero mass particle from the electron. When photons with
energies above twice the electron rest mass pass through matter, they create
electron/positron pairs. So if neutrinos of mass 0.07 eV exist why don't
photons
of energy > 0.14 eV create neutrino/antineutrino pairs? (And how would optics
be different if they did?)

The same question could be asked about photons producing electron
positron pairs, of course, and of course they do (even by photon-
photon scattering). The process is difficult to observe, and it
has no serious consequences for optics on the terrestrial scale,
though it can lead to a horizon effect for gamma ray bursts. Thus
the neutral current process you suggest may exist, but may be
difficult to see.

For myself, I'm going to wait until I can read an understandable
account of this Super-K evidence before declaring the neutrino
(any neutrino) to have mass. Until then I suggest you all read
the papers on atmosphric neutrinos and contemplate the question I
pose below.

(What follows is from a note I sent my son this morning)

{

Thanks. I've read some of the papers, but I haven't found this result.
It apparently concerns the interpretation of atmospheric neutrino
events. There is no mention anywhere of MSW, but it would seem relevant
concerning neutrinos from below the horizon. I really don't expect
anything very convincing to come out of this. It is an attempt to scoop
SNO. I think they needn't have bothered; data from SNO won't show up
for three years.

One thing is curious, and the APOD is another way of looking at it. If
you look at Fig. 2 in hep-ex/9805021 from the preprint archive you will
note that only a small fraction (<10%) of the neutrinos detected by
Super-K are solar. The "solar neutrino problem" arose from data
collected by Raymond Davis in an isotropic instrument. He had no way of
deciding that a neutrino came from the Sun or elsewhere. There's no
indication of spectral differences between solar and other neutrinos
though I'm sure such differences exist and are important in some sense.
I can't see detecting the effect in this background, however.

I wish an expert would wander through. If you get one, please ask for me.

}

It bothers me greatly to see this news media event. These guys aren't
announcing their result on the publication date; they're announcing
that they've submitted it to PRL! Aside from demonstrating their lack
of taste, it also demonstrates their deviation from previous practice
since these things used to show up in the LANL preprint archive. How
can we possibly understand anything from a newspaper article,
especially one with evident errors?

Leigh