The Gallium Anomaly: A Mystery That Has Defied Physics for 35 Years; Understanding

Having a silver metal that melts in the palm of your hand making gallium one of the preferred elements for practical demonstrations in educational and scientific experimentsThe phase change that makes the element “fun” is due to its low melting point of around 29.76 °C, just above room temperature.

But when it comes down to it, this so-called “weak metal” also has some extraordinary properties, such as forming alloys with other metals with lower melting points, such as mercury and cesium. Gallium is widely used in electronics. in the production of semiconductors and LEDs and other research in physics and chemistry.

In physics in particular, one of the two isotopes of the element used in the search for solar neutrinos gives rise to a phenomenon known as “solar neutrinos”. “gallium anomaly”This is actually an observed discrepancy between the amount of neutrinos detected in laboratories and the values ​​expected according to the standard model of particle physics.

What happens to neutrinos in the gallium anomaly?

Neutrinos are strange particles: They have no electric charge, but their mass is so small that it was theorized for years to be zero. Known as three “flavors” (electron, muon and tau), neutrinos can travel across intergalactic distances because of their low interaction with matter. Hundreds of trillions of them may be passing through our bodies without us even realizing it.

When a gallium-71 atom interacts with an electron neutrino, it causes a nuclear reaction that causes the subatomic particle to decay into germanium-71 and release an electron. However, unlike gallium, this isotope is radioactive and unstable. It decays back to gallium-71 in 11.4 days.

The good news here is that this decay can be measured, meaning scientists can track the number of germanium-71 atoms formed to know how many neutrinos were initially captured. But this is where the problem arises, because the amount of germanium-71 was less than expected, and fewer neutrinos were captured than expected.

Does a sterile neutrino explain the gallium anomaly?

The gallium anomaly was detected in 1989 in the so-called Soviet-American Gallium Experiment, which lasted until 1999. In 2001, another experiment called GALLEX began in Italy, which also pointed to a gap in germanium production. Even an event held in 2012, BEST (Baksan Sterile Transition Experiment), exposing gallium to neutrino-rich chromium resulted in 20% to 24% less germanium.

BEST, which investigated the existence of a possible sterile neutrino that interacts only through gravity, found no evidence to support the hypothesis that this hypothetical particle would have a mass one-fifth that of an electron. That is, it discovered nothing except: If neutrinos are sterile, they will likely have a larger mass than previous research suggested.Q.

This doesn’t even mean that sterile neutrinos are the solution to the gallium anomaly. There could be some additional detail that the researchers missed, or an unprecedented explanation that requires new physics. Regardless, the mystery remains.

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