Re: The neutrino has mass?!

Greg Billock (
Mon, 8 Jun 1998 16:17:30 -0700 (PDT)

Loren Haarsma,

> community to "expect" to find neutrino mass. There was another
> experiment, a year or two ago, which reported a neutrino mass in a
> measurement good enough to convince many (most?) physicists. It sounds
> like the Japanese collaboration really nailed the mass measurement -- an
> impressive experiment. Cosmologists and particle theorists have been
> ready and waiting for this piece of data for some time.

I haven't read the original article, but in seeing some comments
from people on newsgroups, it looks like the paper is based on
conversion between neutrino types that have passed through the
atmosphere (IIRC) and the inferred values are not based on new
observations, but on data looked over the course of the past few
years. Everyone is saying that the inferred masses are too light
by about two orders of magnitude (in the most natural interpretation)
to account for dark matter, which might gratify cosmological
constant people, or mixed model people. (The tau-nu needs to
be ~50eV to account for dark matter but assuming Me << Mmu << Mtau
gives Mtau ~ 1eV I think.)

> perhaps, slightly different laws of physics). Inflation theory makes a
> few predictions which non-inflationary cosmology does not make,
> predictions which are matched by observations. That doesn't mean
> inflation is necessarily right, but it does make it worth paying
> attention to.

There is a machine I walk by every day on the way to work which is
meant to answer the question. :-) One of the big differences is
in the CBR-deviation angular spectrum, which this telescope (destined
for the new observatory complex in Chile) is going to measure. That
spectrum should resolve the various cosmologies based on inflation,
the current mutation of superstring, and probably more, by being
able to put tight bounds on cosmological constant, density, and so
forth. I think it is scheduled to go operational before 2000, and
they are already getting some preliminary data in testing from
out in the auto pool lot. :-)