Electrons Are Practically Immortal

Borexino detector. Borexino collaboration/INAF

Electrons are one of the building blocks of the universe, carrying the negative electric charge around the cosmos and allowing us to enjoy all the pleasures of modern life. The stability of the electron has never been in question, but putting a limit on its stability allows scientists to better understand the fundamentals that govern our existence.

So, in a new study, Italian researchers looked at potential electron decay using the Borexino neutrino detector for 408 days. They found nothing. No electron decay. That is good news, because it confirms that the conservation of charge is one of the fundamental laws of the universe.

The team was also able to estimate a minimum lifespan for electrons based on the results from the experiment. An electron life is 66 Yottayears (6.6x1028 years) or 5 billion billion times the age of the universe. The findings are published in Physical Review Letters.

The Borexino experiment is a special neutrino detector buried deep within Gran Sasso, an Italian mountain 100 kilometers (60 miles) from Rome. Borexino is filled with an organic liquid rich in electrons (about 1032, or 100,000 billion billion). A hypothetical electron decay will produce a photon and a neutrino, and the detector has 2,000 photomultipliers that can sense the emitted light. No detection matched the expected model. Reporting on this might seem silly, but experiments that discover nothing are still very important in physics.

Decay is a habitual phenomenon in physics, with heavier particles decaying into a lighter one. These decays tend to follow precise rules, and heavier particles tend to decay into smaller ones. Electrons are the smallest particles with charge; anything smaller (neutrinos, photons, gluons) is neutral, so there’s no way for it to decay into anything else without violating the conservation of charge.

Speaking to Physics World, Gianpaolo Bellini suggested that if all the sources of background radiation were accounted for, the minimum lifetime could be boosted to over 1031 years.  

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