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Better Neutrino Detection Through Beta Decay November 9, 2016

Once upon a time scientists studying the sun couldn’t have the faintest idea of the internal activity of the Sun. One bright (see what I did there) scientist realized that monitoring neutrinos, the massless, chargeless, non-interacting particles that zip through the universe barely interacting with anything at all, might give a useful clue to the machinations therein.  I mean, they knew neutrinos are part of the solar flux,so it’s just a matter of detecting massless, chargeless, non-interacting particles.

Oh, crap.

Well, luckily neutrinos do not remain neutrinos forever; they decay into detectable particles…eventually.  Not often to be sure, as billions pass through a square centimeter every second without leaving any decay particles. Those decay particles can be detected with rather elaborate photomultipliers in a huge cavern in Japan somewhere: “It consists of a tank filled with 50,000 tons of ultra-pure water, surrounded by about 13,000 photo-multiplier tubes. If a neutrino enters the water and interacts with electrons or nuclei there, it results in a charged particle that moves faster than the speed of light in water. This leads to an optical shock wave, a cone of light called Cherenkov radiation. This light is projected onto the wall of the tank and recorded by the photomultiplier tubes.1“ Despite the heavy hardware only a few thousand are detected every year, which should tell you something about the likelihood of a decay event…not very damn likely.

Thing is, the theoretical number and the actual number didn’t match; the experimental result was one-third of theoretical, indicating something must be wrong with the theoretical understanding, or the experiment is crap. It turned out that neutrinos oscillate among three forms (electron, muon and tau) and detectors were primarily sensitive to only electron neutrinos.

Here’s where science gets really intricate; pour another shot and I’ll tell you why. In a distantly-related field, other scientists observed variations in the rate of beta decay of radioactive elements.  Once again, either the data is crap or the theory, and the theory says the decay rate should be constant.  Looking at the data over time, they found that the beta-decay rate matched the neutrino data, indicating a one-month oscillation attributable to solar radiation. Many now believe that neutrino emissions from the Sun are somehow affecting beta decay.

If that’s not strange enough for you then feature this: the same guys who figured this out are going to use beta-decay experiments here on Earth to monitor massless, chargeless, non-interacting neutrinos, and thereby the Sun.

1. Sometimes I don’t feel like writing all that much.  It is 11:30p.m. and I’m tired. Sue me.

Homework:  P. A. Sturrock et al. Comparative Analyses of Brookhaven National Laboratory Nuclear Decay Measurements and Super-Kamiokande Solar Neutrino Measurements: Neutrinos and Neutrino-Induced Beta-Decays as Probes of the Deep Solar Interior, Solar Physics (2016). DOI: 10.1007/s11207-016-1008-9