Neutrinos Key to Understanding Why the Universe Has so Much More Matter Than Antimatter

Matter and antimatter may not be symmetrical after all.
Loukia Papadopoulos

Physicists have come a long way in understanding the Universe, but there are still some mysteries that elude them. One such mystery is why there seems to be so much more matter than antimatter.


A balance violated

Thanks to new research, they may have just stumbled upon an answer, according to Nature. It all started in 1956 when nuclear-weapons physicists Clyde Cowan and Frederick Reines discovered the neutrino.

At the time, in a commentary for Nature, the researchers called it “the smallest bit of material reality ever conceived of by man." This led to Russian physicist Andrei Sakharov introducing a mechanism for how the balance between matter and antimatter might have come to be violated ten years later.

Sakharov implied that the symmetry between matter and antimatter was not perfect, which may have led to a surplus of matter during the cooling that took place after the Big Bang.

Now, an article-physics experiment called Tokai to Kamioka (T2K) is indicating that Sakharov may have been right. The experiment sees neutrinos generated at the Japan Proton Accelerator Research Complex (J-PARC) at Tokai and fired underground.

From there, the generated neutrinos travel 295 kilometers towards a neutrino observatory called Super‑Kamiokande. In this observatory, a giant water tank captures the light emitted as neutrinos interact with the water.

In ten years, T2K detected only 90 neutrinos and 15 antineutrinos. This number is so small because neutrinos have a very small chance of interaction.

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T2K then evaluated both the probabilities that a neutrino would oscillate between different physical properties and that an antineutrino would do the same. The researchers speculated that if matter and antimatter were symmetrical, the probabilities would be the same.

T2K found that they were not. The experiment detected a higher likelihood that neutrinos would change properties and a lower likelihood that antineutrinos would do the same.

As exciting as these results may be, it should be noted that they do not satisfy 5-sigma (5σ) levels of confidence. So, for the time being, they still count as preliminary observations. Time will tell whether they turn out to be true or not.

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