Proc. Neutrino Astrophysics - MPP Theory Group

2030: Neutrino Thermometer
Now we’re getting to some harder stuff, real challanges for the next generation of experimentalists.
As you know, the 7 Be neutrinos from the sun are essentially monochromatic, coming
from an electron capture process. However the Be nuclei in the center of the sun are moving
around due to the high temperature, giving a spread and shift of the line. A calculation [3]
gives the shift as 1.29 keV. A measurement, performed perhaps by comparing with a terrestrial
source, would give the temperature in the center of the sun, an amusing use of neutrinos
as a thermometer.
2040: Neutrino Geology
Around this time we see the active development of neutrino geology. The various radioactive
processes in the earth give rise to neutrinos (actually anti-neutrinos, except for the neutrino
“line” from electron capture in 40 K). Measurement of these terrestrial neutrinos will give
a direct snapshot of the energy production in the earth and allow us to answer many interesting
questions of geophysics and the thermal history of the earth. Since the coherent
superconducting detector provides a light and portable instrument, local and “tomographic”
studies will be possible, as well as the investigation of the planets and their moons. I set this
relatively late since the background from solar neutrinos and probably also nuclear reactors
must be well understood to see this signal (see Fig. 11 of Ref. [2]).
2050: Extra-Galactic Neutrino Burst Observatory
Now we’re getting to the big stuff: the extra-galactic neutrino bursts. If we had a detector that
could see the neutrinos from stellar collapse in nearby clusters of galaxies we wouldn’t have
to wait decades for the next event. With a thousand galaxies in the Virgo cluster at 10 Mpc,
we will be having them every few weeks and supernova neutrino observations will become a
systematic affair. This will permit the study of many interesting points, such as flavor “echos”
due to mixing, tests of CP for neutrinos and so forth [4]. The enormous distance involved
means various time-of-flight effects due to neutrino masses are greatly magnified (in fact there
is a danger this could become too much of a good thing since too much spreading of the pulse
could make it disappear into the background [5]). Such a detector, or perhaps we should say
observatory, is very ambitious, but not inconceivable. With the coherent scattering process
and cryogenic detection to see the small recoils, about a megaton of cold material could
suffice [5]. An alternative idea is the “magic mountain” or OMNIS [6] where neutral-current
induced neutrons from natural Ca are the signal. The joker in these proposals, as usual, is
background.
2050: Neutrino Technology
It took the laser about 50 years to get from the lab to the checkout counter at the supermarket.
Since neutrinos are more difficult than photons, let’s give them a hundred years from their
discovery to get into the economy. About mid-century, then, the light and portable detector
will allow us to monitor nuclear power stations from the outside and to make geological
investigations for minerals and petroleum. Here again an understanding of the background
is essential. I’m not so sure about the sometimes mentioned neutrino telecommunication
channel, because I don’t know what the transmitter is supposed to be.
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