A strange gap between theoretical predictions and experimental results in a major neutrino research project could be a sign of the elusive “sterile” neutrino – a particle so silent it can only be detected by the silence it leaves behind.
It’s not the first time the anomaly has been seen, adding to previous experimental data pointing to something strange in the world of neutrino research. This time it was detected during the Baksan experiment on sterile transitions (BEST).
Unambiguous evidence of the hypothetical sterile neutrino could provide physicists with a solid candidate for the universe’s mysterious stash dark matter† On the other hand, it could all just come down to a problem in the models used to describe old school quirky behavior neutrinos†
That would also be an important moment in the history of physics.
“The results are very exciting”, say Los Alamos National Laboratory physicist Steve Elliott.
“This definitely confirms the anomaly we’ve seen in previous experiments. But what this means is not clear. There are conflicting results now about sterile neutrinos. If the results indicate that fundamental nuclear or atomic physics is being misunderstood, that would be very interesting as well.” to be .”
Despite being among the most abundant particles in the universe, neutrinos are notoriously difficult to catch. If you have hardly any mass, no electrical charge, and make your presence known only through the weak nuclear force, it’s easy to slip through even the densest materials unhindered.
The ghostly motion of the neutrino isn’t its only interesting feature. Each particle’s quantum wave changes as it progresses, oscillating between characteristic “flavors” that echo their negatively charged particle cousins - the electron, muon and tau.
Studies on the oscillations of neutrinos at the US Los Alamos National Laboratory in the 1990s noted gaps in the timing of this flip-flop that left room for a fourth flavor, one that wouldn’t cause as much as a ripple in the weak nuclear field.
Shrouded in silence, neutrino’s sterile taste would only stand out for a brief pause in its interactions.
BEST is shielded from cosmic neutrino sources under a mile of rock in Russia’s Caucasus Mountains. It features a double-chambered tank of liquid gallium that patiently collects neutrinos that erupt from a core of irradiated chromium.
After measuring the amount of gallium converted to a germanium isotope in each tank, the researchers were able to work backwards to determine the number of direct collisions with neutrinos as they oscillate through their electron flavor.
As with the Los Alamos experiment’s own “gallium anomaly,” researchers calculated a fifth to a quarter less germanium than expected, suggesting a deficit in the expected number of electron neutrinos.
This is not to say for sure that the neutrinos had briefly assumed a sterile taste. Many other searches for the pale little particle comes up empty-handed, leaving open the possibility that the models used to predict the transformations are misleading at some level.
That in itself is not a bad thing. Corrections in the basic framework of nuclear physics can have significant consequences, opening gaps in the Standard model which could lead to explanations for some of the great remaining mysteries of science.
If this is indeed the hallmark of the sterile neutrino, we may finally have evidence of a material that exists in enormous quantities, yet makes only a gravitational pit in the fabric of space.
Whether that’s the sum of dark matter or just one piece of the puzzle would depend on further experimentation with the spookiest ghost particles.
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